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SpectraFoo User`s Guide

1. Channel Names Reset Channel Hames Figure 5 1 Analyzer Control amp Routing The Analyzer Control amp Routing window allows you to control the global properties of SpectraFoo s analysis engine The Master Controls window allows you to add delete and configure specific instruments h O Master Controls O Real Time Rack O soto Transfer Function gt Spectragram gt Spectragraph gt TC Clock gt Level Meter gt Oscilloscope gt Power History gt Envelope History gt Band Power History gt Phase Torch gt Lissajous gt Power Balance gt Correlation gt Correlation History gt Code Meter gt Code Matrix Meter gt Code List Meter gt THD Errar Figure 5 2 Master Controls window The Master Controls window contains two types of items Instrument Classes and Instrument Controllers In strument classes contain a disclosure arrow the name of an instrument type such as spectragraph level me ter etc and an add button Instrument controllers contain from left to right a visibility checkbox an on off button a solo button a show details button a channel assignment and a remove button In the picture above the Real Time Rack item is an example of an Instrument Controller and the Spectragram item is an example of an Instrument Class To the right of each instrument class is an add button Clicking this button adds an
2. The final function computed by the transfer function measurement system is the coherence The coherence is a measure of how much on average the response signal lines up with the source signal on a frequency by frequency basis This is one of the most important pieces of the puzzle because it allows us to evaluate the quality and usefulness of the data Coherence is a little hard to understand so we ll examine it in a little more detail About Coherence Imagine the source signal is a simple sine wave The response signal will in general be another sine wave with the same frequency but a different amplitude and phase Mathematically 67 The Transfer Function s t sin 211ft r t asin 2rftr Figure 4 23 Coherence expressed mathematically The source signal s t is a sine wave with unit amplitude and frequency f The response signal r t is a phase shifted sine wave with amplitude a and frequency f These two signals are shown below the source signal is green and the response signal is red dp Figure 4 24 Simple source and response signals Even though there is a phase shift between the source and response the phase shift is constant in time On average the signals line up the same way all the time On the other hand if the signals are not related to each other Figure 4 25 Simple source Complex response signal In this case the phase shift between the source and response signals changes over time T
3. This pop up menu allows you to choose how the response traces are faded 1 None Don t fade the response traces 2 Coherence Fade the color of the trace based on the coherence of the measurement 3 Age Fade the color of the trace based on how long it has been since the source signal exceeded the threshold level Show pop up menu This pop up menu select from a number options Each option is independent of the others 1 Coherence Trace Is Visible Shows and hides the red coherence trace 2 Show Details Shows and hides the numerical readouts of the center frequencies and levels of each of the bands when the analyzer is in octave analysis mode 3 Smooth Traces Makes the Transfer Function perform averaging in frequency space to display smooth response traces This generally makes the response traces easier to interpret Compute Delay button creates a new Delay Finder window and computes the impulse response of the system that is currently being measured The Delay Finder will automatically compensate for the delay in the SUT Coherence The Transfer Function window has a Coherence trace which is displayed as a red trace in the power vs frequency display Coherence has a value of O when the trace is at the bottom of the display and has a value of 1 when the trace is at the top of the display and varies linearly in between Coherence is a measure of how well the response signal correlates with the source signal
4. Use dBu Calib Accumulatit ULN 2 Digital 1 4 Resolution ULN 2 Digital 2 Reset Peak Holds Show Trac n c a Gl 1 instant Ml 2 Peak mA 2 avg 2 Instant o Rate Arg Mode Log H Settling Time 2 039 5 Frequency pr Power Scaling Frequency Range 0 Hz 17 42 kHz e Se ca Rape 2 125 250 ilk 2k 16k Pe wane 2832 16 70 6d 58 32 46 40 34 28 lt 2 16 10 4 Figure 5 4 Channel assignment The details window is accessed by clicking the show details button in either the Master Controls window or in the instrument itself The Master Controls window allows you to have as much or as little analysis as you need It also allows you to completely personalize your configuration SpectraFoo remembers the configuration of windows and rack panels After you have set up a personalized configuration SpectraFoo will launch using that configuration until you make a change You can also save and recall different window configurations by using Window Sets which are covered later in this manual You can hide and show the Master Controls window from the Window menu or by using a key command A Analyzer Control Routing Analyzer 4096 Ft 10Hz al d of Analyzer Channels 4 E Input Matrix Ana 1 ULH 2 Digit a Ana 2 ULH 2 Digit H Mode Horm Hay Ana 3 ULH 2 Anal rey Ana 4 ULA Analo he Mode Horm HH Output Matrix Cut 1 Internal 1 E Dut 2 Internal Z 8 Out 3 nic Ha
5. The unit of spacing on the frequency scale determined by the doubling of frequency centers The common octave centers are 8 16 31 62 125 250 500 1 k 2 k 4 k 8 k and 16kHz Unit used in the measurement of resistance and impedance Often used with prefixes to indicate large values such as k kilo which equals 1000 for example 5 kQ means five thousand ohms or 5 kilo ohms Similarly M mega is used to indicate 1 000 000 so 10 MQ means 10 million ohms or 10 megaohms The maximum energy of a signal Describes the position of one sound wave relative to another or in relation to time Let s look at phase between two signals In the first example the two signals have the same phase 117 Glossary Figure 186 0 Phase offset The two signals are drawn perfectly on top of each other In the next example the right signal is 180 out of phase with the left signal When the audio on the left is at its highest the right is at its lowest and vice versa A signal that is 180 out of phase is also called polarity inverted or phase inverted Figure 187 180 Phase offset If we sum the signals together we get nothing the high of the left is cancelled out by the low of the right This is called phase cancellation 118 Pink Noise PPM RMS S Signal to noise ratio SUT THD VU Glossary Figure 188 Phase cancellation Random noise that has been run through a pi
6. Meter scales 24 Orientation 19 PPM ballistics 23 Sum amp Difference mode 21 Link Groups 87 Choosing what groups an instrument belongs to 89 Disable 89 Enable 89 Naming and configuring 88 Lissajous Phase Scope Adjustable sensitivity 46 Auto Sensitivity Mode 47 Change mode 46 Hi Res Mode 47 Stereo Position mode 46 Vectorscope and X Y modes 45 Main menu 105 Preferences 105 Master Controls window 76 O Oscilloscope Selectable trigger channel 44 Single and Dual trace modes 43 Trace display modes 43 P Parameter Management System 85 Phase Torch 47 Power Balance History 45 Power History 44 Preferences All clicks bring instruments to front 106 Always run at full speed 106 Automatically bring all windows to front 106 Automatically Show Delay Finder Name Dialog 106 Automatically switch hardware sample rate for captures 106 Cursor Keys 106 Font 105 Horizontal Window Grid 106 Instrument Graph Background color 106 Instrument Window Cursors Always Track Mouse 106 Instrument Windows have Window Frames 105 Make control windows float 106 Panel Color 105 Panel Highlight Tints 105 Use 64 bit Analyzer 106 Use brushed metal panels 105 Use OpenGL 106 Vertical Window Grid 106 S Sample Rate 108 Saving and recalling presets 85 Signal Generator 90 Arbitrary signal sample rates 94 Building Files amp Captures 94 Dither amp Quantization 92 FFT Synchroni
7. SpectraFoo User s Guide SpectraFoo User s Guide Metric Halo Revision 1656 Publication date Date 2012 04 30 13 49 05 0500 Mon 30 Apr 2012 Copyright O 2011 Metric Halo Table of Contents Pi a A O O ctaaateete So nha erat acest ats asain a Memeearcomesreees 11 Coneratla O A AI 11 About SpectraFoo COn Uri SS 11 N 11 OY SUS ln REQUITC eS rt ectn cutee eines Reaver Ais au aloha attains anya Noes E ads 12 Zi CCU ak OOD ASICS ite oN oat E iain eae Nien da Ao o 14 Getinge TOs NOW ope CTA OO Ate oe ae A iS 14 Common Features lAs rune is A E E NN 14 Common Features Control WAM COWS sszrsesisi rerin AAA AE 15 Wie Real IMIG Nac coc ooi cas 16 Real Time Rack Consolidated VieW iii A A AA I7 D a E US E E E A AE ASS 18 SIS CU lOO anda a arar eats E N A E E E eed tae eet ida eet 18 Specta Foo Complete su aa A A a a iii 18 LA A E E NTN RAN EN 19 A E cE aaa enema 19 User Definable Over Digital Clip Counter cccssccssccssccesccnnsceeeccntsceascensecesceenconness 20 SUM Diference Meter MOO Ci a 21 Detailed Readout and Hold Indicator Controls oooccooccnoccconcnnncnnnncnnncnnnccnnncnnnncnnncnnncnnnnos 21 ODON VV IMGQOW as cada 21 PRIDE 23 Mero CaA S a E ya ane ica e e ad 24 User selectable meter bar colors isan ida 24 Meteribar color transition leves aaa 25 STDS Bi Ve 21 0 nena POPE O cates casas eet lg aia deste ns lu esalic ed duet see eee tet aman ook 25 CVT NON ET P an to TT P E E E EE E T E AS
8. 7 Workflow Features Overview SpectraFoo has a suite of features integrated into the application to help you manage the workflow of utilizing the wide variety of tools included Since there are so many instruments and parameters that may be controlled in the SpectraFoo metering system and different engineers have different preferred methods of working Spec traFoo provides comprehensive parameter management facilities at many different levels in the application The lowest level of parameter management is implemented with the pervasive link group mechanism Link groups allow you to easily arrange to keep multiple instruments and their parameters linked together so that adjustments to one instrument are automatically reflected in all the instruments that are included in the same link group Link groups also allow you to link instruments selectively only linking the desired parameters The next higher level of parameter management is the parameter library management system Each instrument type has a parameter library associated with it and you can create your own parameter presets to store in the library All presets are available to all instruments of the same type This mechanism allows you to establish a set of customized settings for your favorite instruments Window Sets The highest level of workflow management is provided by the Window Set system Window Sets allow you to save all aspects of SpectraFoo s configuration including inst
9. 70 Meas urine OV STEIN RESPONSE nd do 71 STE O ONEC UON ea 73 Transfer Function Snapshot Overlays Reference cccssccseccntsccnsccnssceneccnsccntsceascnsscaascenssensess 73 Cursors 0 the Tranter FUNCUON WINDOW erii a a a 75 5 Controlline Audio a a NS tumen aeaee e E E E aetna soem maera es 76 Ana Ver COMUO SARONIO triss a a aa a a a aa 76 AIS ZEE C AnNa on E A A 78 Adjusting th Number of Analyzer Ghannels did a e e a ah 79 Chaneine the drasos dao 80 Conn Unne UNE TOUS MaX TE E 80 Difference monitoring 10r all MSMUIN CIS seese a a e E O E ES 82 Routine theSignal Generator Output SFC e a a 83 PARC A a E E O 84 PAN O OWN F AUE aa a n a a a r a 85 A A ce Rua see 85 Window S ea o o a te cl da epale al 86 E CSO IO PPP NR 87 B Sie A sian E I E E onmagle T EA T nist EE E 90 NENT soil 90 DIVCCO AOC SING N INE S eaa r a a aa earbansuesmtaas 90 Additive white noise with sweepable level vi E 91 Additive pink noise with sweepable level iia 92 Diner QUAMUZALION ena E EEA 92 i OV ONZ OR ae a aa teaciensaentweehdaads 93 ICO WE UI A e dado 94 Alar senal sample mates ainia 94 Bula me Fiesse CAplures atan dla lata 94 CONTO Ste dE NICO lia indias 96 REG so O O O 97 Recordin CAU eolica 97 Load Ines Audio eS Or CAPO tallo ias 99 Capture sE WINE tds ita 99 CAPS OEI A O lalo 99 Understanding the Overview WINdOW viniese n Ei e ai 100 Measuring time between two events iaa dlls soles 104 NO 104 COIE Menu REFER OI CO raa aaae E A E E A
10. Hanning Window Hamming Window Blackman Window Figure 8 9 Selecting the Rectangular window from the FFT Window library 93 Signal Generator 2 Choose Rectangular Window from the Window Library pop up menu Now the analyzer will use the rectangular window for all future analysis This will provide single spectral line analysis for synchronized sines Switch the window back to Hanning Hamming or Blackman before you begin analyzing music or unsynchronized tones Windowed Bursts You can burst the generated signal using the burst controls You can specify the length of the burst in millisec onds and the period of burst repetition in seconds You may also specify whether or not the burst is wndowed When you enable bursting the underlying generated signal is passed for the period of time corresponding to the burst length and then cut off The signal stays off for the time remaining in the burst period It will then be passed again for the period of time corresponding to the burst length Burst Time ms 125 Burst Period Window Figure 8 10 Bursting Controls If the Window checkbox is checked the burst is not abrupt but is instead faded up and then faded out with a raised cosine window If you are bursting sines it is a good idea to use the window since it is possible to generate clicks if you do not have the window enabled AAA Overview Bursted White z Draw Dual Trace a Capture Name Bursted White Start 00 00 0
11. Timecode Clock The Timecode Clock is currently not operational Correlation Meter SpectraFoo s Correlation meter is a standard tool for reducing the complex relative phase information between two channels to a single number between 1 and 1 Correlation is a measure of how well two signals line up with each other When two signals have a correlation of 1 they are the same signal Similarly when two 49 Instruments signals have a correlation of 1 one is the inverse opposite polarity copy of the other When two signals are unrelated to each other they have a correlation of O Mathematically the correlation is the average of the sign e g or of product of the two signals The SpectraFoo version of the correlation meter has a relatively fast averaging time to give you a clear picture of the correlation at any given time To understand how the correlation is changing over time you can use the Correlation History meter Figure 3 60 Horizontal Correlation Meter As with the Level Meters the Correlation meter can be put into a vertical or horizontal orientation to meet your tastes When the meter is in a vertical configuration it can be docked to the left side of the Correlation history meter See Docked Correlation History Correlation History Meter The Correlation history meter provides you with a time history of the correlation meter This allows you to see how the correlation evolves over time and can help you
12. 2 Octave power is displayed as bars each band is one half of an octave wide 1 3 Octave power is displayed as bars each band is one third of an octave wide 1 12 Octave power is displayed as bars each band is one twelfth of an octave wide 1 2 3 4 1 6 Octave power is displayed as bars each band is one sixth of an octave wide 5 6 1 24 Octave power is displayed as bars each band is one twenty fourth of an octave wide 7 Continuous power is displayed as a continuous curve Frequency Range Slider You use this range slider to control the visible bandwidth of the transfer function Power Range Slider You use this range slider to control the visible power range of the transfer function The power scale is automatically scaled to keep the display logarithmic Frequency Scaling Slider You use this slider to control the scaling of the frequency axis of the transfer function Avg Rate Slider You use this slider to control the averaging rate of the transfer function analysis The far left end of the slider is No averaging and the far right end of the slider corresponds to averaging over 2 minutes approximately The averaging done by the transfer function is a decaying exponential average so it is difficult to assign a numerical value to the averaging rate For some measurements e g ones with very little noise like measuring an EQ you can use faster averaging rate closer to the left hand side of the
13. 252 277 7013 as applicable 8 TRADEMARK RIGHTS Permission is hereby granted to use the phrase Mastered with SpectraFoo M and to use the SpectraFoo logo on CDs LPs CD ROMs DVDs cassettes Laser Discs and Films for commercial release that were produced using this software Any visual representation or reproduction of SpectraFoo generated graphics must be given credit using the terms Measured using SpectraFoo 9 GOVERNING LAW This license agreement shall be governed by the laws of the United States and the State of New York If for any reason a court of competent jurisdiction finds any provision or portion thereof to be unenforceable that provision will be enforced to the maximum extent permissible and the remainder of this Agreement shall continue in full force and effect SpectraFoo SpectraFoo Visual Audio Monitoring System Metric Halo Real Time Rack and Phase Torch are trademarks or registered trademarks of Metric Halo Distribution Inc All rights except those specifically grant ed here are reserved All other trademarks are the property of their respective owners 113 License Agreement Should Licensee have any questions concerning this Agreement please contact Metric Halo in writing Manufacturer Metric Halo Distribution Inc 5 Donovan Drive Suite 1 Hopewell Junction NY 12533 USA 114 Glossary Symbols A Boost Cut dB DUT FFT Gain Hertz Delta meaning change For example
14. 46 40 34 28 22 16 10 4 Figure 3 10 Spectragraph Second Traces pop up Accumulation modes SpectraFoo s underlying FFT generates more data than can be displayed on screen at once The way that this data is treated when the system computes the trace is called the accumulation mode SpectraFoo provides two accumulation modes that you can choose using the Spectragraph Controls window i 5pectragraph Controls Factory Default H Groups 1 4 Channel 1 57343 Digi 4 Channel 22 5734 4 Second Traces Che White Noise is Flat Calib Pink Noise is Flat gt pm Resolution Continu Holds m E 1l Arg m dl 1 Instant ccumulation Mode O 2 Peak MO 2 4 wg mA 2 instant lll Rate Awg Mode Log Hi Settling Time Taare Frequency sar Power Scaling Frequency Range 0 Hz 16 10 kHz THA SIE ra ele ee A ee E cae 81631 62 125 250 500 dk 2k E Power Range F N 8 32 16 r0 6d 58 52 46 40 34 28 22 16 10 4 Figure 3 11 Accumulation Mode pop up 1 When the Accumulation Mode is set to White Noise is Flat the Spectragraph shows the maximum power of all of the spectral lines in the FFT that fit into each point in the displayed trace This has the effect displaying white noise or noise that has an equal amount of power at each frequency as a flat line This mode is traditionally used when the frequency scale of the graph is linear 2 When the Accumulation Mode is set to Pink Noise is F
15. AOS MMC Mac il taa 117 e R T ON 118 AO da E E AE E E E E E en AE EA E A 118 NB BPN ASC EE O E E I E TE gums E E S E A E E A 119 List of Tables le Level Meter OPIO Sa la alada 1070 1 PAPA e A E E E O A eens A aos COG serie AAE EEr O ialbeie ti 10 1 Introduction Congratulations You are now the owner of the most powerful audio analysis and metering system on the planet SpectraFoo is capable of monitoring up to 24 separate channels simultaneously depending on your input hardware You may be asking 24 channels all at once How is this possible The answer is that SpectraFoo uses Metric Halo s ultra efficient high resolution analysis engine This technology uses the power of your Mac s processor in conjunction with your audio hardware to provide blazingly fast and incredibly detailed sample accurate analysis and metering of any channel or an entire mix SpectraFoo technology is unique in its ability to provide you the engineer spectral power and phase analysis which is truly useful to your production tasks About SpectraFoo Configurations SpectraFoo is available in two configurations SpectraFoo Standard provides a comprehensive set of real time metering instruments For most mixing and monitoring tasks SpectraFoo Standard contains all the tools you will need It gives you a comprehensive multi channel view of signal levels wave form data signal histories spectrum analysis and spectral histories and a variety o
16. Accumulation Snapshot of Bit Matrix The meter can be switched into an accumulation mode by clicking within the instrument The accumulation mode does not erase the bit matrix with each new time slice and this accumulates a picture of all of the sample codes that have been exercised by the signal Normal program material will generate an accumulation that looks like the corresponding figure above This snapshot shows us that while most of the codespace is exercised by the signal the top 3 dB or so is pretty sparse This indicates that we could compress this signal with a pretty hard ratio and a 3 dB threshold and introduce very little distortion Since the Code Matrix Meter shows you the utilization of the code space it can help pinpoint problems with processing algorithms e g skipped codes etc and can be used in designing and testing DSP algorithms Code List Meter The Code List Meter displays a list of the codes of all of the samples in the time slice This allows you to see low level activity in the signal stuck bits DC offsets and the like When you resize this window it attempts to create an equal number of equal length columns of samples length of the column is determined by the height of the window and the width of the window is computed automatically the width that you set is ignored 52 Instruments Column 2 3 4 5 6 7 8 64 Samples per Column Figure 3 68 Bit Scope Layout with 512 Sample Time Slice and 8 Col
17. If you have a very old Mac it may not support Quartz Extreme and if this is the case you will not be able to take advantage of the OpenGL optimizations available in SpectraFoo e A CoreAudio compliant audio I O device Many USB devices including the Macintosh Built In Audio are implemented as two separate devices one CoreAudio device for input and one for output You will need to create an Aggregate Device in the Audio Midi Setup utility to configure multiple CoreAudio devices to appear to SpectraFoo and all other CoreAudio clients as a single unified device SpectraFoo s physical I O capability and supported sample rates are controlled by the audio hardware you choose to use with SpectraFoo For best results and the highest degree of compatibility testing out of the box we recommend that you use a member of Metric Halo s Mobile I O Family of Firewire audio interfaces 13 2 SpectraFoo Basics Getting to know SpectraFoo SpectraFoo provides you with a wide variety of audio monitoring and analysis instruments You may access any combination of the instruments at any time This allows you to use as much or as little analysis as you want The following section describes the instruments available to you and how they work Please refer to the Section on Control and Routing to learn how to control the flow of signal through SpectraFoo Common Features Instruments All of the instruments have the following controls e A power
18. SPECT acid Vertical Oneto iO ais 39 3 38 Using the Spectragram and Spectragraph together occooocccocccnnccnnccnnncnnncnnnncnnncnnnncnnncnnncononcnnncnnnnss 40 3739 SDECIASTAMT prelerences ia OS a o dada 40 340 Power scaling setto OS arta pi A NA 41 Se POW caline Sel TOMA AA 41 OAs Wieserine Oscos ope aa is 41 JA OSCIOSCODE COMUGIS at a da 42 3 44 Oscilloscope running in dual trace mode oooccoocccocccnccnnnccnnncnnncnnnncnnncnonocnnncnnnrnnnncnnnrnnnccnncnnncoss 43 SpectraFoo User s Guide DAS OCSCIOSCODe COMMONS WINDOW aii 43 AO POWECIAMISUONY pus eccdieneneeacdss au sacanenernansadeans 44 De EY A cesar tnaema See uee a seta name aeouenipeenremecotiert 44 Di Ost OW IES ALAIN E Tal ss e Dl 45 DAD Lissajous Phase SCOPE vector INOUE sitios 45 J50 Lissa ous Phase Scope X INOUE seriedat cltls letras 45 du le Lissa ods iv Stereo ROSItoOn MOTE siper noon dei 46 302 ss a OUS CONTO IO a E 46 E 47 2 945 PRISE LORE COntrolWINCOW cepe a AR 48 2 5 oe phase Torc M WIth thres hold alt 60 dB ai aaa a wert aceuinatnateuentts 48 ase TOCA ger O E hat al aarc case at d abaccei re teaatelen el can atncatar 49 2 Dana PO WEer ESO parisina 49 007 Bana OWE Histon COMMONS israel tdt dl sao las 49 2109 Ve ical Comtelation Meter nda A 50 3 60 Horizontal Corelio Meier is 50 HO COME ATION ASTON ap papa 50 3702 DOeked C orela on eFON estad adolece 50 207 16 Dit stional IMs Me COC Meter uu did ros 51 3 64 Denntionsotr theo
19. TE A E E T 25 Dual canelo A i A E Aaa See 26 Sum Mu lipiand Overlap MOS ts 27 ACCU MUA NON AOC CS aaan a AS 28 Physical Unica A AS a 29 ca O O teats cca een dace nets 30 JET ANC ANS A A ee 30 Los ana linear an CAG UIA does 33 Spectral Snapshots Overlavs Sc Libraries A kaa aes 33 SA E ASAE CUA ROPE RNC SNE orc SRE Wenn ar E ST tear neat een nr E Ree ne een eRe 38 OSOS Cea oa 41 O 41 Smelecana Dual chale Modest ad 43 Trace CHG AN Oeste iia 43 Selectable tiege Chanel Aa 44 POV CI ey SLO OE ORCOS E E A 44 Envelope ISto a bs 44 a ls y Co ame ena eR A A Renee EN 45 ss TOUS ARAS CO Prode 45 Vectorscoperana Ad MODEeS aaa ac sido iaure selene vets ueteal viel dues delineate iaciaaieiisolentia 45 Stereo POSITION MOIE N 46 AQUUStAD CPS STIS ILIV a aed ato weer E E E E EE E 46 AO SENSITIVITY MOOG A OS 47 PEROT MOUE pias 47 PRSE TOCA a a a T 47 Band PO We IS T E eared eddie iseerae tpi sten bee 49 SpectraFoo User s Guide UME CORE Cloacas otitis 49 Cone Mete e llos 49 Comelatonmalstony IWIClCE ee laico dii odds 50 COS Meri a Te e eta 51 Code Mato Meteored 51 E EN E E AR PE quo E eek E Pace E E Baa eae 52 THRBMSter usado a ASA ASA A 53 A MMS ASE AC leo Aan 55 COVETVICW NN 55 ASTOR PONCHO CONTOS pda llas 58 a hel comer mre rarer Mer pe ender ete NG ere ee ne eee ee ee ee 60 the Troner FCC HOM te 60 Understandineine Transe FUNCOM eiii lisis 62 Eer Ne ne Darle allioli peto Ds canciod 67 ADOUL INE RESPON EEC UNNOS dial il adi
20. The phase response can help determine what type of equalization will best solve the problem and also help determine if other phase changing com ponents like the crossovers of a system are causing problems It will also help you determine if the drivers in a speaker or a cluster of speakers are properly time aligned as shown before The basic system configuration that we will use to measure and correct an acoustic reproduction systems is Signal Source Figure 4 29 Measurement and Correction setup 70 The Transfer Function The equalizer in this setup is used to correct the response of the system The switch above the pre amp is used to select between the output of the equalizer and the output of the test mic Measuring System Response 1 Open the Transfer Function window if it is not already open Open the Transfer Function Controls window Flatten the system equalizer or bypass it We want to measure the un equalized response of the system Set the response input channel to the output of the test mic You can do this by selecting the proper input channel in the Transfer Function Controls window if you are using multi channel input hardware or by routing your test mic to the computer input using an external routing system e g a patch bay or a mixer Set the transfer function source channel to your signal source and turn on your signal source Make sure that the signal source is a broadband source like pink noi
21. and the Detrig Lvl field indicates the level threshold that will stop it These levels and times are visualized in this illustration Trigger Level Pre Trigger Time Post Triaqer Time Triggers Here Detriggers Here Capture Starts Here Total Length of Recording Figure 10 3 Level based Capture envelope parameters 98 Capture Ends Here Capture and Storage If the Auto Arm box is checked SpectraFoo will make a new capture every time the audio input breaks the trigger level once the Record button has been pressed If the Auto Arm box is unchecked Spec traFoo will make a single capture 3 Timecode based auto punch NOT FUNCTIONAL AT THIS TIME All captures are retained in RAM to assure the highest processing speed and complete random accessibility Loading Audio Files for Capture SpectraFoo can also load existing AIFF and SDII audio files into RAM for use as a capture You may only load files that are small enough to fit in the memory of your computer You can load an audio file into memory as a capture via e the Open command in the File menu e the Load Capture command in the Capture menu SpectraFoo can read split stereo SDII and AIFF files if they conform to a specific format If the files meet the expected format they will automatically be assembled into a stereo capture 1 Both files or the pair must be of the same type 2 Both files must be mono sound files 3 Both files must be in the
22. as library files The library file that is created does not contain the actual audio samples that the spectragraph was analyzing but rather the trans formed Fourier power data that the Spectragraph uses to draw its traces This allows you to take spectral snap shots of sounds and post process them at a later time You can take a number of snapshots and average them to form a new average snapshot You can also use a pair of snapshots to create a transfer function which can be displayed in the Transfer Function Window SFC To take a spectral snapshot 1 Route a sound that you want to take a snapshot of to a Spectragraph 33 Instruments J 00 i D 2 EEJ SS ny de Li Figure 3 25 Spectragraph Snap Button 2 Click the Snap button on the left side of the Spectragraph The Spectral Snapshots dialog will appear Spectral Snapshots taken at Thu Aug 11 2005 8 00 38 PM Trace Set 1 Trace Set 2 Name Name save Snapshot of save Snapshot of C Instantaneous inst Instantaneous inst M Average avg Y Average avg Y Peak pk Fal Peak pk Comments Cancel Figure 3 26 The Spectral Snapshots dialog 3 Name the snapshots The Spectral Snapshots dialog has two name fields one for each trace set of the Spectragraph The first trace set is composed of the three traces associated with the first input channel The second trace set is composed of the three traces associated wit
23. bring all windows to front M Make control windows float Ed Use OpenGL _ Instrument Window Cursors Always Track Mouse Instrument Graph Background Color Horizontal Window Grid 3 Cursor Keys Command L Option Shift Ed Control El Automatically Show Delay Finder Name Dialog El Automatically switch hardware sample rate for captures El Always run at full speed Figure 11 1 Main Preferences Table 11 1 Main Preferences Panel Color Sets the base color for instrument panel borders Use brushed metal panels controls the appearance of the panels that appear within the Real Time Rack consolidated view Panel Highlight Tints allow you to adjust the brightness of the highlights and shadows on the instrument panels Instrument Windows have Window Frames When enabled this will add the standard Mac OS window frames to instruments when they are creat ed Font Sets the font used for instrument panels when they are created 105 Quick Menu Reference All clicks bring instruments to front When enabled only clicks to the instrument s border will bring it to the front When disabled any click on the instrument including its control buttons will bring it to the front Use 64 bit Analyzer Sets whether SpectraFoo will use 32 or 64 bit calcu lations This should be enabled unless you are run ning on a very slow computer Automatically bring all windows to front When enabled clicking on an instrument will bring
24. captures to a fresh location or with a fresh name You will be presented with the save dialog for each capture in turn The Load Capture command allows you to load any AIFF or SoundDesigner II file as a capture The Delete Selected Captures removes the selected in the Capture List Window captures from SpectraFoo s memory If the Ask About Unsaved Captures command has been selected for each capture that has been changed and is being deleted SpectraFoo will ask if you want to save the changes A capture that has never been saved is considered to be changed The Ask About Unsaved Captures command when checked causes SpectraFoo to ask you if you want to save a capture that has been changed or has never been saved before it is deleted from memory The state of this command is remembered as a preference You may want to turn this off if you have made a large number of captures and want to delete them all or quit SpectraFoo without being asked about each capture in turn Groups The Groups menu allows you to control and select from the library of instrument enable groups Instrument enable groups allow you to take and restore snapshots of the state of the enable and solo buttons of all of the instruments in the Real Time Rack Unfortunately the Instrument enable groups do not currently support instruments that are not in the Real Time Rack The Add to Group Library command allows you to take a snapshot of the current state of the buttons and save
25. e Frequency Scaling sets the scaling of the frequency display Far left is linear far right is logarithmic e Power Scaling sets the scaling of the power display Far left is linear far right is logarithmic 40 Instruments Figure 3 40 Power scaling set to logarithmic Figure 3 41 Power scaling set to linear e Frequency Range sets the low and high frequency limits that the Spectragram apply to the display e Power Range sets the low and high power limits that the Spectragram apply to the display e The Color Power calibration bar allows you to quickly determine the color of audio events as referenced against the audio scale set by the Power range control Oscilloscope Overview The oscilloscopes are single trace style scopes which provide a display of the program waveform of the as signed input channels Pressing the details button on the oscilloscope brings up a Control window with several adjustable features such as trigger mode If the oscilloscope is contained within the Real Time Rack you can Stereo link the two oscilloscopes with the SLink button on the left channel scope When you click the SLink button the control parameters for the right channel scope are set to the corresponding values from the left scope iada Digital 1 4 0 4bdm3 44911 S04 er S Figure 3 42 Triggering Oscilloscope Within the Oscilloscope details window is the Sensitivity slider which controls the magnification of the oscil loscope
26. in writing to be bound by the terms of this License Agreement 4 LIMITED WARRANTY ON MEDIA MH warrants that for a period of three 3 months from the date of purchase the media on which the Software is furnished will be free from any physical defects in materials and workmanship and that the Software program is properly recorded If the Software is not recorded or contains physical defects in materials and or workmanship 112 License Agreement MH will at their option either a replace the item at no charge to the Licensee or b the purchase price of the product provided Licensee follows the MH return procedure and returns the item to be replaced postage prepaid with proof of purchase to MH For warranty service please write or call MH at 727 725 9555 for Instructions 5 EXCLUSIONS OF LIABILITY IN NO EVENT WILL MH BE LIABLE FOR ANY DIRECT INDIRECT SPECIAL INCIDENTAL OR CONSEQUEN TIAL DAMAGES RESULTING FROM ANY DEFECT IN THE PRODUCT INCLUDING LOST PROFITS DAM AGE TO PROPERTY AND TO THE EXTENT PERMITTED BY LAW DAMAGE FOR PERSONAL INJURY EVEN IF MH HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES FURTHER MH DOES NOT WARRANT GUARANTEE OR MAKE ANY REPRESENTATION REGARDING THE USE OR THE RESULTS OF USE OF THE MH SOFTWARE OR WRITTEN MATERIALS IN TERMS OF COR RECTNESS ACCURACY RELIABILITY CURRENTNESS OR OTHERWISE THE ENTIRE RISK AS TO THE RE SULTS AND PERFORMANCE OF THE SOFTWARE IS ASSUMED BY THE LICENSEE So
27. it into the library A dialog will appear that allows you to name the Group By appending a x where x is replaced with the command key that you would like to use you can assign a command key to the group For instance the Al Off group was defined with the name All Off 0 The Delete from Group Library command allows you to remove a snapshot from the library Selecting any of the items that appear below the separator line will restore the associated snapshot Window The Window menu allows you to control the various windows that comprise SpectraFoo The windows in SpectraFoo are in two different layers These two layers consist of instrument windows and control windows that float above the instrument windows The Control and Routing window Master Control window FFT Window Control window and the all the Details windows for the real time instruments are control windows Instrument windows are used to display 109 Quick Menu Reference actual measured data The Real Time Rack is also an instrument window Control windows always stay in front of the Instrument windows In order to help you manage the windows and reduce screen clutter SpectraFoo provides a set of menu and keyboard commands These key commands are covered in Appendix II at the end of this manual The Stack Windows command re arranges all of the windows in the instrument layer by stacking them diago nally from the upper left hand corner of the main screen T
28. loop handle Click and drag to change the loop points in realtime As you drag the loop handle around the loop point will update instantaneously You don t even have to let go of the mouse button e A This field shows the change in time between the loop start and end times This is also represented by the purple area within the ribbon e Draw Dual Trace Clicking this check box will cause the envelope ribbon to display the left and right channels superimposed on top of each other e Do Data Slicing Clicking this check box will cause the slice of data that lies underneath the cursor to be displayed by the realtime instruments This is described in the Data Slicing section Peak L 23 20dB RMS L 27 36dB Peak R 24 46dB RMS R 27 96dB P f L LF 2 06 kHz 1 HF 2 22 kHz 93 50d8 P f LF 2 06 kHz HF 2 2 z 95 4 Figure 10 9 Capture Overview Window Ribbons e Envelope The Envelope overview shows the amplitude envelope history of the captured waveform This is a very common display for digital audio editing and can be a helpful point of reference You can zoom in to display the capture on a sample by sample basis When captures are played back the cursor moves across the ribbons until it gets near the end of the window At this point the ribbons begin to scroll very smoothly creating the effect of animation As a result when you have the envelope overview zoomed in all the way and play the
29. of samples that SpectraFoo uses in its FFT analysis Increasing the number of points increases the frequency resolution of the analysis it allows you to see narrower spectral features especially on the low end but it tends to smear the high end in time and can lead to a desynchronization of the audio from the analysis Metric Halo recommends using either a 4096 pt or a 8192 pt FFT Analyzer depth for music production work Changing the analyzer depth is simple Just select the desired depth from the Ana yzer pop up menu in the upper left hand corner of the Analyzer Control amp Routing window This control is also available in the Analyzer menu The change takes place automatically and instantly 1024 Pt 40Hz O 2048 Pt 20Hz ALE Routing wv 4096 Pt 10Hz of Analyzer Channels 4 Hig 8192 Pt 5HZ frix Anat Le 16k Pt 2 7 Hz k 9 Mode Nom ina3 UL 32k Pt 1 3 Hz 2Digit D Mode Norm F 64k Pt 0 7 HZ farrix y Channel Hames Reset Channel Hames Figure 5 9 Changing the analysis depth Configuring the routing matrix Once you have selected your audio input path you should configure the routing matrix to remove any ambi guity from the process of monitoring your audio If your audio path is two channel the default configuration is probably fine Left Channel named Left Right Channel named Right If you are using a multi channel input path the first step is to name the input channels SpectraFoo pr
30. pair of channels as well as analyzing each channel separately This can be useful for a number of applications including looking at the comb filtering caused when a stereo pair is summed to mono 82 Controlling Audio and Instruments B Analyzer Control amp Routing m Analyzer 4096 Pt 10Hz 4 fof Analyzer Channels 4 HE Input Malbrix Anal KICK E Anaz OHL Hy pde Norm Ana3 OHR FP Ana 4 RHDS 5 Mode amp Output Matrix nu Outi YOX 1 4 Dut Z ACOUS H Qut3 nie 4 Qut 4 nic He FAA A gt A Channel Names Reset Channel Names In 1 KICK In 2 OHL In 3 OH R In 4 RHDS In 5 SHR TOP In 6 SAR BOT In YOX 1 In E ACOUS Figure 5 13 Sum Difference pair modes menu To analyze the sum and difference of a pair of channels 1 If the Analyzer Control Routing window is not visible show the Analyzer Control Routing window by selecting Show Routing Window from the Window menu 2 Each pair of channels has an associated mode menu on the left side of the Analyzer Control amp Routing window Select amp from the channel pair Mode pop up menu To analyze each channel in the pair separately 1 If the Analyzer Control Routing window is not visible show the Analyzer Control Routing window by selecting Show Routing Window from the Window menu 2 Each pair of channels has an associated mode menu on the right side of the Analyzer Control Routing window Select Norm from the channel pa
31. same folder 4 Both files must have the same name with the exception that one filename ends in L and the other in R If the files do not match these criteria they will not be automatically opened and reassembled SpectraFoo will not prompt for the location of the second channel of the pair if it is not found automatically Capture List Window A list of the captures that are currently available is maintained in the Capture List Window found within the Window menu The Capture List maintains a library of the captures that are currently loaded into RAM Clicking on a capture name selects it Double clicking on a capture in this list opens a Capture Overview window which will be described later The Capture List window behaves like a standard Macintosh list You can use the shift and command keys to make multiple selections If you have multiple captures selected and double click a Capture Overview window will open for each selection AAA Capture List Hane o Start o End Dur Bass Crum aiff 06 4 02 03 06 41 07 11 03 08 Capture 1 06 47 33 14 06 47 56 185 03 04 o 2 06 47 352 04 06 41 59 18 01 14 Figure 10 4 Capture List Window Capture Overview Windows The recorded information can be further analyzed and manipulated via the Capture Overview windows Cap tures can be removed from memory to reclaim the space for more recordings The total length of captured material is limited only by the amount of RAM in your system Once
32. sum and the right bar is the difference if the meter is in the vertical orientation if the meter is horizontal the sum is in the top bar and the difference is in the bottom bar The level meter mode is selected with the Meter Mode pop up menu which allows you to configure a meter to run as a straight level meter or as a Sum amp Difference meter Detailed Readout and Hold Indicator Controls The Level Meter Controls window also contains detailed numerical readouts for the Peak RMS and VU levels for each channel Next to the labels for the readouts there are checkbox controls These controls allow you to determine whether or not to display the associated hold indicators on the meters Options Window The rest of the meter configuration controls are in a second control window called the Level Meter Options window You access this window by clicking the Options button at the bottom of the Controls window Clicking the Options button brings up the Level Meter Options window 21 Instruments O Level Meter Options YU Settling Time 0 293 s FFH Settling Time 1 705 YU PPR Peak Float Size 4 Hold Release Time 2 005 Meter Scaling Tick Spacing 3 00dE Scale Type SpectraFoo 43 dl Use Level Based Color Ed Draw Peak Level as Bar M Use PPM ballistics M Draw Holds as Arrows Draw YU as Solid Bar Ed Auto Release Holds Use AES Std RMS Ref Use Solid Color Transitions Safe Until 30 00 dEFS a naaa 5522 r0 r0 44 5
33. the Lissajous Control window Phase Torch This is a revolutionary tool which compares the phase difference between two channels as a function of frequency independent of power The display looks like a multicolored fountain or torch The graphing scheme is a polar pattern The radius from the center is determined by the frequency and the angle is determined by the phase difference between the left and right channels The center of the graph represents DC while the outer radius represents the Nyquist value In order to help you intuitively identify the frequencies the phase points are also colored according to their frequency You can get a color frequency calibration chart by clicking on the Phase Torch s parameter control button and viewing the relationship between the Power Threshold s power scale and the frequency range in the color bar A mono in phase signal is indicated by what looks like a torch precisely aligned with the Y axis of the scope The in phase torch illustrated below fuzzes out at high frequencies because the signal used to create the display did not have very much high frequency energy so the display is dominated by noise at high frequencies An out of polarity signal appears as a negative version of a mono signal Delays appear as spirals within the scope Nulls in the Comb Filter In phase Out of Polarity Inter channel delay Figure 3 53 Phase Torch This meter is very useful when recording a m
34. the noise floor to decrease with decreasing frequency This has the effect of decreasing the noise where it is most audible while still removing the distortion caused by quantization 92 Signal Generator TE E Aye 16 bbb FS Spb ee m ae IA Ea bb dodedo A edit nindn h bh odo Preece Teale Atos a ta OS CE a Ora T Li du Figure 8 7 Dithered 16 bit signal FFT Synchronization Each of the frequencies of the generated signals can be synchronized to the analyzer width allowing you to generate test tones that can be analyzed with no FFT windowing for the best level accuracy Synchronize Figure 8 8 Synchronization Controls Synchronization is enabled by checking the Synchronize checkbox When synchronization is turned on the generator will not sweep the sine parameters it will only use the parameters entered in the start column The parameters for the two noise sources will continue to sweep If you have turned on synchronization you can select the Rectangular window for the system analyzer This window will allow the analyzer to recognize that the synchronized sines fit exactly into one analyzer spectral line To select the rectangular analyzer window 1 If the FFT Window window is not visible make it visible using the Show FFT Window Control command from the Window menu Oo FFT Window FET Window SS E Add to Library Delete from Library Rectangular Window Triangular Window lie
35. the other hand if the coherence remains low for a variety of microphone positions the cancellation of the source signal is not due to a specific reflection but is actually part of the system response In order to correct these types of problems either the configuration of the system must be changed e g moving the position of the speakers or adjusting the relative time delay of different clusters in the system or the configuration of the acoustic space will have to be changed removing reflections adding diffusion etc About the Response Curves If the SUT is a simple processor like an equalizer the power response tells us the effect of the processor on the signal Hopefully the response matches the expected response In any case the measured response is the actual response of the processor If the SUT is a sound reinforcement system the expected or more to the point desired response of the SUT is that of a wire The system should ideally reproduce the signal exactly without any coloration No real system will do this but often the problems in a sound system are correctable The data provided by the transfer function allows us to determine 1 What parts of the system are correctable with equalization 2 What equalization is required to correct the system As described above the coherence allows us to determine what is correctable with equalization The power response tells us what equalization is required to correct the system
36. to spend some time listening to and looking at your favorite music music that you know really well After a relatively short amount of time details of the recordings such as phase structure overall spectral balance dynamic range frequency range and low frequency roll off will literally leap out at you You will be experi encing rather than thinking about quantitative analysis 25 Instruments Peak Hold Trace Displays the maximum amplitude per frequency bin since the peak hold was last reset To reset the peak hold either click on the instrument itself or click on Reset Peak Holds in the details window 4 AUS Sh e 3231 62 125 250 500 tk 2k 4 ieee awe Averagelrace Displays the average These checkboxes show and hide solo level of the signal at each frequency the traces allowing you to focus O Spectragraph Controls your attention on any combination H of traces it ia ees a A Instantaneous Trace Displaysthe current Channel 1 57343 Digi Channel 2 15734 level of the signal at each frequency Second Traces Channel 2 4 _ Use dBu Calib Accumulation Mode Pink Noise is Flat 4 Resolution Continuous Reset Peak Holds Click to reset the peak trace Sets the averaging rate for the average trace When you move this slider the ballistics of the average trace will change in realtime Use these sliders to change the low and high frequency lim
37. to track down specific phase problems by allowing you to see blips in the phase correlation at the same time you hear the events that cause the blips For example if the correlation dips every time the snare drum hits it is very likely that the channels that contain the snare are causing the problem Maybe you need to time align the snare mic with the overheads or maybe that return on the bussed compressor needs some delay compensation Other tools in Foo like the Phase Torch can help you track down the solution to the problem The Correlation Meter and the Correlation History Meter can help you find the problem Figure 3 62 Docked Correlation amp History 50 Instruments The centerline on the Correlation History Meter corresponds to a correlation of O while the top edge corre sponds to 1 and the bottom to 1 respectively The Correlation Meter in its vertical orientation can be docked to the left side of the Correlation History Meter providing both instantaneous and historical data in one com posite instrument Code Meter The Code Meter is the first of three sample code metering tools included in SpectraFoo Complete Along with the Code Matrix Meter and the Code List Meter they provide a comprehensive set of sample code metering tools that can show you the nitty gritty details of your digital signal stream These tools can be used to check for among other things DC Offset sample word width Stuck Bits Codespace utilizat
38. trace allowing you to see the wave shape characteristics of very low level signals The Timebase slider controls the timescale of the oscilloscope grid The timebase of the grid is precisely indicated in the numerical readout at the top of each scope Each mark on the slider indicates the number of samples represented by each pixel in the trace 41 Instruments a Oscilloscope Controls Factory Default 4 Groups none E Channel 1 37343 Di 4 Channel 2 57343 Di Hy Ea Trace 1 Color E Trace 2 Color Mode Dual Trace HH Sensitivity Timebase 1 E Thx 1024 BOND Trigger Mode Free Slope Trigger Level A Mo Retrig Time Firm Trigger Trig Chan 1 ES z Grid Grid Yert Spacing Grid Horiz Spacing A AN H LIJITEJITIJITIEII I offset A AN HOftset NN AOD AN illumination Figure 3 43 Oscilloscope controls Each oscilloscope can trigger and hold the wave form of the signal being monitored There are seven available trigger modes Table 3 2 Trigger modes Normal triggers the drawing trace once channel input match es your trigger settings Hold triggers a drawing trace and holds the signal until rearmed Hold and Retrigger same as Hold but the trigger is automatically rearmed Timed Hold same as Hold but the trigger is automatically rearmed after the desired retrigger time Polarity Check same as Hold but displays all the data prior to the trigger point and tri
39. use this tool for a variety of purposes One application is for measuring system response with an RMS average instead of the normal vector averaging that is used by the transfer function This can allow you to measure approximate system response in the case where the system time delay is not constant e g outdoor systems in a windy environment etc This functionality can also be used to make transfer functions between unrelated sound sources two different songs noise floor of two different rooms etc Spectragram The Spectragram utilizes the same FFT resolution and scale as the Spectragraph The display medium correlates not only frequency and power but also time The result is a visual sonic fingerprint Like the Spectragraph the true power of this instrument lies in its synchronization with the live audio signal After spending some time calibrating your eyes to your ears by watching the Spectragram while listening to music which is intimately familiar the instrument literally becomes a waterfall of musical information This tool is very effective for precisely identifying frequency overlap and masking effects such as a bass drum track and a bass track occupying the same frequency range and obscuring each other It gives you a good picture of the rhythmic aspects of program material and is very helpful in pinpointing timing problems in dense arrangements 38 Instruments Figure 3 36 Spectragram horizontal orientatio
40. 0 000000 Length 00 00 01 001337 End 00 00 01 001337 Cursor 00 00 00 371519 FU Do Data Slicing gt Details gt Calibration 5 00 00 00 000000 2 00 00 01 001360 A 00 00 01 001360 Window Start Window End gt S Figure 8 11 1 second of 125 ms bursts every 1 4 of a second Overview Windowed Bursts AOAO Capture Name Windowed Bursts Start 00 00 00 000000 Length 00 00 01 001337 Draw Dual Trace End 00 00 01 001337 Cursor 00 00 00 371519 Do Data Slicing gt Details gt Calibration 5 00 00 00 000000 3 00 00 01 001360 A 00 00 01 001360 Window Start Window End AA See gt Figure 8 12 1 second of 125 ms windowed bursts every 1 4 of a second Arbitrary signal sample rates You can tell the signal generator what the sample rate of the eventual output hardware will be This is controlled with the Sample Rate edit text box All of the times and frequencies in the signal generator will be scaled relative to the generator sample rate This can be used for special effects e g generate a 88 2 kHz signal and play it through 44 1 kHz hardware or to generate signals to be used on high density hardware like Sonic Solutions Building Files amp Captures You can generate Signal Files or Captures directly from the signal generator The buttons in the lower right hand corner of the signal generator are used to issue these commands 94 Signal Generator _ file gt tae TT
41. 0 500 ik k dk k 16k Power Range TO TO a a Oc A 28 82 76 70 6d 58 52 46 40 34 28 22 16 10 4 Figure 3 18 Spectragraph display Resolution pop up The Resolution pop up does not affect the resolution of the actual FFT analysis being performed it only affects the way that the FFT data is displayed To control the resolution of the FFT you still use the FFT size commands found in the Analyzer menu Here are some examples of the different modes pow gt O mmn NAN KO Sd t 1 g TERA Figure 3 19 1 octave display resolution 1 i ra 3E D i g 1 t a I 7 3 4 i ss D i g 1 t a 5 n a P Figure 3 20 1 2 octave display resolution 31 Instruments BRET ss Opm nova E ion 1 3 octave display resolut Figure 3 21 AAA KOLO O TO e mae no nal ion resolut isplay 1 6 octave d 22 3 igure F E ion resolut isplay 1 12 octave d 23 3 igure F 32 Instruments 43 66 69 D fe 72 o EE E 78 tE E sjer n 1 30 a 1d 102 amp Solo Figure 3 24 1 24 octave display resolution Log and linear averaging There are two natural ways to average the power spectrum of an audio signal The first method which corre sponds to SpectraFoo s Log Averaging Mode averages the power data after it has been converted to decibels It is consistent with a visual average of the trace in the display and mathematically it correspon
42. 096 Pt 10Hz pude Sof Analyzer Channels 4 by Input Matrix na 1 KICK Ana2 OHL 43 Mode Horm Hi Ana OHL Ana 4 RHDS FF Mode Norm OH R Output Matrix ourt RHDS PR ow2 acous 43 owa SNRTOP 7 oura nie H dl NR BOT 3 Reset Channel Hames In 1 ed In 2 OH L A acous In 3 In 4 RHOS n c In 5 near In 6 SHR BOT In f YOX 1 In ACOUS Figure 5 11 Named analyzer channels 81 Controlling Audio and Instruments The number of analyzer channels determine how many different channels you can analyze at once If you need to analyze more channels at one time see the section on changing the number of analysis channels If you just want to quickly switch analysis to a different one of your input channels use the analyzer channel pop up menu Note that you do not have to stop the transport to change the routing from within SpectraFoo Each instrument in SpectraFoo is assigned an analyzer channel that it gets its analysis data from The Active Channel pop up menu in the control window of each instrument is used to select the instrument s source analyzer channel O pecao apn Controls Factory Default HA Groups 1 He hannel 1 KICK CPE Channel 2 OHL Second Tra OH L H Use dBu Calib Accumulati OH R Noise is Flat Resolution RHDS B Reset Peak Holds Show Trae M C E 1 Instant 2 Instant Average Hate Avg Mode
43. 105 MAIN oi 105 o O 107 SpectraFoo User s Guide El IO 107 AY O E RO 108 A A caee yet a seeps A een oes 108 ECE riot sd dl od cales 109 GOUD sunia a souas dimers A tueearatevn guess atuns 109 O O 109 A AN 111 e LICE EARI CEMENT uena a ts co 112 GlOSSal E E E TATE ET EE nies tan A E EI E S E E 115 WNC e E E chen dear TA E E E E A 121 List of Figures Z le POWE DUON A e eco eat esa aaa are 14 SOON A A otto eae aha ee otras 14 AN O O e co 14 2A Real Time Rae Control DUONE AS 15 2 5 Active Channel pop up menu with custom channel names ccseeeeeeeceeeeeeeeeeeeeaeeeeeeeaeeeaeees 15 2 6 Instrument Groups Menu Only applies to instruments in the Real Time Rack occooocccnccccnnccnnnicos 16 A A O A I7 Sl Level Meter Horizontal Orientation A T E E eras 19 D2 Level Meter Vertical Orientation ti A N 19 3 3 Digital Level Meters Peak RMS and VU meters w Clipped Sample Counter occoocccnccnnncnnnccnnncnnns 20 ALONE COUTO ti A E dd 21 30 Level Meter Controls WINTON bon Gas O 21 370 Level Meter Options VV WAC OW ti A Ai 22 dl Level Meler Options VVINGOW sua da NN A o 24 330 The SPECI AS ADI and CONOS id ic 26 3 9 Spectragraph showing the left and right channels Of a Stereo pair oocccoccccoccconcnnnccnnncnnncnnnncnnncnnnnss 27 3 10 Sp ctragraph Second Traces POPUD sesei iirinn A elda Moree Oscawesees 28 Ss AccUmalati n Mode POP UP srian ia a E a E anairendeeas 28 A a WIEP MIS EAE AA E A dontaaesineen
44. 6 TOR Manta Cape Ode ala rios 97 OZ MeV ele basco Cap e Mode at lio ia 98 10 3 Level based Capture envelope parameters cc sccsssccssccesccnssccesscnteceaesenssceasscnssceaesenscnssceees 98 10A Caption 99 LOS sce Captures Overview VV INOW at laa 100 10 07 Capture OVerviewWINdowS TOP a 100 OO o a U OE A ET ciles denen ately tana Raarend aioe saea ta amaian tins 101 TO 8 OOO EMC A ET E EA A E E T siet A E E E E E A E E T 101 10 9 Capture OVEN ew WINGOW RIDDOMS serial lili nia 101 SpectraFoo User s Guide TOS 0 Capture Overview Window BOUON isa 102 TO Miles FOP AAA A O A E E A 102 A II etl ce a E A tn acta essen seeesae 102 OA Play TOI A o ts 102 OA Al Dic IOC E I E I E EAE E E E S S E A E E E E eTA 102 TO e PEON O O A 102 LOGEC Play Baca nte tido add 102 TOs OOP BACK AMG o AAA A e A A T 102 TOMADO i 102 LOS Play Once Between LOOP FOIN caia adas 102 TOO ZOOM OUG nnar a a a a ual blue Doel uae secenaasnliaias 103 ISA A E A T AE N EN 103 TO GUON Aids 103 10 232 Auto mat on pomt Move menti00l sedal linia 103 10 24 Automation pont DENCH AOC tecate 103 OS PP once seers aac iat det eocal A antes acemiuae 103 TODO do ChOSSIACE dado taa 103 10 275 NUMEIC Time Selecionar sa ia ia laos 103 MIA IN 104 IA CEC e E 105 12 Key Command WINdOW aia 107 MS COMMA MSY Calor een ideo soil orale 107 TA hardware ConMeurationWAndOW us cad 108 ARO aa POR ree eer teen ene en mre E er rene ere ears rt ee 116 TBA o AOS qlo 185
45. 8 2 6 40 34 2 22 16 10 Caution Level 15 00 dEFS O a TTT 2062 76 70 64 8 2 46 40 34 5 2 16 10 Danger Level 1 00 dEFS ERES 8 32 r0 P0 4 358 2 46 40 ee 22 16 10 E Peak pws ru Figure 3 6 Level Meter Options Window The table below describes the controls which are available in the Level Meter Options window Table 3 1 Level Meter Options VU Settling Time slider Controls the settling time of the VU indicator When the slider is set on the VU mark the indicator will use VU ballistics This parameter is global for all channels and meters in the system PPM Settling Time slider Controls the settling time of the level meter when Use PPM ballistics is checked This parameter is global for all channels and meters in the system Peak Float Size slider Controls the size of the floating peak indicators PPM Hold Release Time slider Sets the amount of time the Peak Holds wait before resetting when Auto Release Holds is checked Meter Meter Scaling slider slider Sets the Sets the dynamic range of the Level Meter Sets the dynamic range of the Level Meter of the Level Meter a Spacing slider Sets the calibration mark spacing of the meter when the SpectraFoo scale is selected Scale Type pop up menu Selects the PPM standard to use for the meter scale Use Level Based Color checkbox Activates level based transition colors for the meters When this checkbox is unchecked meters use orig inal SpectraFoo color
46. Cluster 1 Enable checkbox Checking this turns on the additive white noise 2 Start Level edit text box The peak level of the white noise at the start of the sweep This level is in units of dBFS and may be positive or negative 3 End Level edit text box The level entered into this box is used as the ending level of the sweep This level is in units of dBFS and may be positive or negative An entry of means use the start value 4 Pre Delay edit text box The Pre Delay time is the period of time that will elapse before the sweep starts 5 Duration edit text box The Duration is the period of time that will elapse between the start and end of the sweep 6 Post Delay edit text box The Post Delay time is the period of time that will elapse after the end of the sweep before the sweep loops around Dither amp Quantization You can control the quantization and dither used by the signal generator in the generation of the signals The generator provides for quantization from 2 bits per sample to 24 bits per sample Quantization is always active and the signal will be truncated to the number of bits specified in the Sample Size edit text box sample Size 24 Bits Dither Figure 8 6 Quantization and Dither controls When the Dither button is checked the signal generator will dither the signal before truncation Dithering replaces distortion with uncorrelated noise The dither in SpectraFoo is noise shaped which causes
47. Log Settling Time 2 039 5 Frequency ae Power Scaling Frequency Range 0 Hz 17 42 kHz MET A Prt Pb rp ety O O el 81631 62 125 250 500 ik zk dk k 16k Power Range SPS TTT TTT 3832 76 70 6d 58 52 46 40 4 28 2 16 10 4 Figure 5 12 Channel names show in all instruments Once you have assigned an input channel to an analyzer channel the input channel s name is propagated throughout SpectraFoo So as you see above the channel names that appear in the instrument Active Channel pop up menu are those of the input channels that have been associated with the analyzer channels If you change the input channel associated with an analyzer channel all of the instruments that are assigned to the analyzer channel will update automatically This two layer mechanism works extremely well when you have a large number of source tracks that you want to alternately apply the same type of analysis to For example lets say that you are mixing from a 24 track master It is unlikely that you would need or even want to do spectrum level and phase analysis on all 24 channels at once But you may want to set up 4 clusters of instruments with each cluster assigned to a different analyzer channel You can easily switch any cluster to any of the 24 master channels by using the analyzer routing control Any of the channels is just a click of the mouse away Difference monitoring for all instruments The Analyzer can analyze the sum amp difference of each
48. Out 4 nic H a gt Channel Names Reset Channel Hames Figure 5 5 Analyzer Control amp Routing Window 77 Controlling Audio and Instruments The Analyzer Control amp Routing window allows you to control SpectraFoo s global analyzer parameters and how signal is globally routed through the analysis system SpectraFoo s analysis routing model has two layers for maximum flexibility e By selecting an audio device from the Audio I O menu s Configure Hardware selection you choose the audio hardware that SpectraFoo uses to acquire the audio streams to analyze SpectraFoo uses the Analyzer Control amp Routing matrix to allocate each of the audio device s signals to any of SpectraFoo s analyzer channels e Each of the SpectraFoo instruments has an internal routing control that allows you to select any of the analyzer channels to feed the instrument This process is illustrated below Audio Hardware j of Analyzer Channels Signal Generator SFC Instrument Active Channel Instrument Instrument Instrument Instrument Display Display Display Display Figure 5 6 Analyzer channel routing Instrument Active Channel Instrument Active Channel Instrument Active Channel Analyzer Channels In SpectraFoo there is a difference between analyzer channels and analysis instruments In SpectraFoo you can have many different types of instruments monitoring the same channel as we
49. Scale Line up calibration is 6 dBu at marking Test Digital PPM Digital PPM Scale Line up calibration is O dBFS at marking 0 SpectraFoo dBu calibrated scale with even spacing of calibration marks CON OO hh UUN The PPM crawlback ballistics in the meters conform to a crawlback rate of 20 dB in 1 7 seconds Fast PPM can be accomplished by setting the PPM settling time to 0 85 seconds User selectable meter bar colors SpectraFoo has two different ways of color coding its meters The first method which corresponds to the original SpectraFoo color scheme provides one color for peak level and another for RMS level The second method called level based color changes the color of the meter bar based on the level of the audio You can change the colors in both of the color coding methods from within the Level Meters Options window To change the Peak and RMS and VU colors for a meter 1 If the Meter s Control window is not visible show the Control window by clicking the Show Controls button and then selecting the Options button at the bottom of the Controls window 2 Click the appropriate color tile within the Controls Window The Macintosh Color Picker dialog will appear 3 Select the new color in the dialog 4 The Peak RMS and VU colors are used for the Peak RMS and VU holds respectively If Use Level Based Color is unchecked the Peak and RMS colors are used for the Peak and RMS meter bars resp
50. Sets menu 2 Unselect the group s associated enable checkbox To enable a group 1 If the Link Groups Window is not visible Select Show Link Groups Window from the Sets menu 2 Select the group s associated enable checkbox To choose which groups an instrument belongs to 1 Display the instrument controls for the instrument that you want to link Groups Spectrum hey gt Figure 7 8 Groups pop up Menu 2 Each instrument control window has a Groups pop up menu in the upper right hand corner To add the instrument to a group select the group name in the Groups pop up menu To remove the instrument from a group unselect the group name in the Groups pop up menu im Contra Spectrum Channels roups Y Spectrum Solo Enable 3 Sero 3 Po 4 5 pe 0 Hz 22 i 6 rT Tt ik 2 T Range 8 IELE TVET de a a ee Figure 7 9 Selecting a group in the Groups Pop up menu 89 8 Signal Generator Overview SpectraFoo Complete has a high resolution multi tone multi noise sweepable burstable signal generator The generator is capable of running in real time or alternatively striping signal into a capture or into an AIFF or SDII file This release of the signal generator creates very high quality signals but it has not been optimized either in computational speed or in interface This means that it takes a pretty significant amount of CPU power to run in real time It can always create striped captures or files The inte
51. Start 00 00 00 000000 Length 00 06 55 817317 J oraw Dual Trace End 00 06 55 817317 Cursor 00 00 41 141619 Hy z l Do Data Slicing Details 7 Calibration 00 00 00 000000 00 06 55 817333 00 06 55 817333 Figure 10 6 Capture Overview Window Top e Capture Name Lists the name of the current capture Click on the lock icon to activate the text field that allows you to name the capture e Details and Calibration Click on these disclosure arrows to show hide the details and calibrations for the overview window ribbons The details provide precise numerical readings of the values of each display at the point of the capture which lies underneath the cursor e Start and End List the start and end times of the capture referenced to the timecode of the source e Length Indicates the length of the capture O Cursor Shows the exact position of the cursor referenced to time 100 Capture and Storage Figure 10 7 Loop Start button Figure 10 8 Loop End button These buttons set the start and end times of a loop loops are shown in the ribbons as a purple highlighted area When you click one of the buttons the timecode value of the current cursor position will be copied into the corresponding timecode field Click in the appropriate field to edit loop start and end points from the keyboard You can also use the mouse to edit loop points in realtime moving the mouse pointer to one of the loop boundaries causes it to change into a
52. The Transfer Function Fa ey ee Transfer Funcion Figure 4 2 Transfer Function of a Room Response with a time delay e The data in the relative power display is invalid because the source and response signal are not time aligned and therefore not really correlated with each other e A jagged sawtooth wave like trace in the phase response display indicates that the source and response signals are not time aligned SpectraFoo provides a delay detection feature that is accessed via the Compute Delay button present in the Transfer Function window The Delay Finder records a segment of both signals and computes the correlation of the signals with each other By moving the cursor to the largest correlation of the two signals you set the system delay and compensate for the measurement delay time aligning the two signals Now the transfer function measurements will be accurate The Delay Finder uses the Fourier deconvolution theorem to compute the impulse response of the signal pro cessing elements that the response signal has passed through The deconvolution theorem allows SpectraFoo to in essence divide the stimulation signal out of the response signal and create the impulse response of the signal processing system being measured The impulse response is the signal that we would measure if we stimulated the system with an impulse e g a loud sharp snap 56 The Transfer Function The impulse response is essentially noise
53. When Coherence is at its maximum value of 1 for a given frequency band the source and response are perfectly correlated and the Transfer Function is completely uncontaminated by noise When Coherence is at its minimum value of O for a given frequency band there is no correlation between the source and response and the measurement in this frequency band is invalid Coherence can be used as a guide to determine which frequency bands are equalizable Frequency bands for which Coherence is low cannot be corrected by equalization Frequency bands for which Coherence is high are equalizable The Transfer Function Window The Transfer Function system provides all the tools necessary to make high quality measurements of simple systems and will allow you to easily measure and correct small scale sound reproduction systems like con trol room monitors home theaters and small club sound reinforcement systems The transfer function environment is contained in the Transfer Function window There is only one Transfer Function window in the system It can be shown like any other instrument in the system using the Master Controls window The control item for the Transfer Function appears as the second item in the list in the Master Controls window The Transfer Function has a small number of controls in the main window Power Ys Frequency Figure 4 6 Power vs Frequency 60 The Transfer Function When Power vs Frequency is set to disclosed
54. _ Captures Load PP k Run j Figure 8 13 Signal generator control cluster The button in the far bottom right corner of the signal generator window controls the real time generators and is labeled either Run or Stop Pressing this key will toggle the run state of the real time generator The button labeled Capture will allow you to create a capture directly from the signal generator without having to loop the signal back You can name the new capture and specify the length in seconds of the new capture Note All captures in the system are currently limited to 16 bits To generate distortion free captures please ensure that you have the bit depth of the signal generator to 16 bits or less and the dither is turned on The button labeled File will create an audio file directly from the signal generator without having to loop the signal back You can specify the name bit depth file type SDII or AIFF and the length in seconds of the new file The button labeled Save saves the current set of signal generator parameters to a signal generator parameter file The button labeled Load loads a signal generator parameter file and resets the state of all of the signal generator parameters to those saved in the signal generator parameter file While most of the functionality in the signal generator is straight forward many unique sounds can be created through creative use of the parameters A number of interesting sample signa
55. able period of time After a short period of time the measurement should settle down If all is well the coherence should be near the top of the graph for most of the audio band If you are using music you may not see much activity in the very high end above 16kHz Click the Take Snapshot button in the Transfer Function window The Transfer Function Snapshot dialog will appear snapshot taken Sun Aug 21 2005 9 33 10 PM Snapshot Mame System LFT crossover null Comments Invert Trace Smooth Trace sll o jus Cancel 0K Figure 4 30 Transfer Function snapshot dialog Enter a descriptive name for the snapshot e g Control Room Response The time and date of the Snapshot is automatically logged You can enter any comments pertinent to the snapshot in the com ments box You can also tell the system to smooth the snapshot data when it is displayed and to invert the snapshot data when it is displayed 71 The Transfer Function Click the Invert Trace checkbox and then the OK button The Overlay List window will appear the list in this figure has a number of overlays yours will have just the new one 000 Overlay List Snapshot Hame Y a Eis al System IFT crossover n gt O System 1FT Top Ol System 1FT hand overh al System al listening posi El Left Cab Close Mic O Dead End L Close O Left Average E Right Average al Total System Average rara O CCRC Gy yD Co
56. actual musical signals can be really annoying when used for acoustic testing and do not allow you to compare what the transfer function is telling you to what you are hearing but they do allow you to make very accurate measurements in noisy environments You can use this type of source signal when you have to test a system while other aspects of a venue are still being set up SpectraFoo s Transfer Function Measurement system needs to see both the source signal and the response signal to build the transfer function The measurement created is a differential measurement and removes all of the common elements of the measurement path You can use an external signal like music from a CD or DAT player a SpectraFoo capture or SpectraFoo s built in signal generator as the signal source SpectraFoo provides an internal loopback path for capture play back and the internal signal generator so you can route the internal signal source back to the transfer function without using one of your A D channels Checking your measurement equipment If you do use the loopback path your system s digital to analog and analog to digital converters D A D path are not common to both the source and the response signal If the frequency response of the D A D path is not perfectly flat in both phase and power its response will color the measured response 63 The Transfer Function You can easily measure your D A D chain by looping back your system s an
57. all instruments to the front When disabled clicking on an instrument will bring only that instrument to the front Make control windows float When enabled control windows will float over all other windows in SpectraFoo but not other applica tions When disabled control windows can be cov ered by instrument panels Use OpenGL Turns on OpenGL graphics support This should be enabled unless your computer does not support OpenGL Instrument Window Cursors Always Track Mouse When checked the cursor in supported instruments such as the Spectragraph will always track the mouse position When disabled the mouse will only be tracked while a cursor key is held down Instrument Graph Background color Sets the color used for the data area of the instru ments Horizontal Window Grid Sets the horizontal spacing of the grid used to help in placement of the instruments in the workspace Vertical Window Grid Sets the vertical spacing of the grid used to help in placement of the instruments in the workspace sor Automatically Show Delay Finder Name Dialog When checked you will be prompted to name each Delay Finder window when using the Transfer Func tion Automatically switch hardware sample rate for cap When checked SpectraFoo will attempt to change tures the S R of the audio hardware to match the sample rate of the capture when playback begins When not checked SpectraFoo will play the capture at the sample rate that is already
58. all the snapshots in the list e Invert All Snapshots Select this command to invert all the snapshots in the list e Uninvert All Snapshots Select this command to uninvert all the snapshots in the list e Show All Snapshots Select this command to make all the snapshots in the list visible e Hide All Snapshots Select this command to make all the snapshots in the list invisible e Ask About Unsaved Snapshots When this item is checked the system will ask you if you want to save an unsaved snapshot before it is removed from memory Cursors in the Transfer Function window You can put a readout cursor in the Transfer Function window by moving the mouse cursor over one of the transfer function panels and holding down the lt command gt key If the display is one of the octave analysis modes the cursor will snap to the center of each band The cursors in both the power and phase panel will move simultaneously To move these two cursors separately hold down both the lt command gt and lt option gt keys To remove the cursor from the display move the cursor to the vertical calibration of one of the panels 75 5 Controlling Audio and Instruments Analyzer Control amp Routing When you first launch SpectraFoo the Analyzer Control amp Routing and the Master Controls windows will appear 3 nal zs Control g Routing Analyzer 4096 Pt 10Hz Hig d of Analyzer Channels 4 Pi Input Matrix Output hati
59. alog output directly into it s analog input Make a measurement using the internally looped back signal generator as the source and the system s analog input as the response The measured transfer function is the response of your D A D chain Internal Signal enerator System Boundary Figure 4 17 Setup for checking your D A D chain If the response is sufficiently flat you can use the internal loopback method If it is not then you must use an external loopback of the source as the source for the transfer function since this will remove the D A D chain from the measurement One of the strengths of SpectraFoo s Transfer Function Measurement system is that it allows you to do Mu sic Based Measurement MBM This means that the system can automatically apply a threshold to the source signal to make sure that it is only measuring the response when the source is actually stimulating the SUT MBM allows you to make accurate transfer function measurements even when the source signal is not station ary like music and when the signal comes and goes in various frequency bands like music MBM builds the transfer function up over time In order to be able to create an accurate measurement of the system response when the test signal is non stationary the response signal and the source signal have to be synchronized in time If the signals are not synchronized the relative measurement of response will be wrong For stationar
60. analy zer Channels aii dio 81 512 Channel names shown alliastuments add dd E 82 SAS UNO Dillerence pair modes Menu ni 83 Os Ta Level Calibrati On DIAE secure coins 84 7 1 Accessing the library system from an instruments Controls WINdOW cccocccocccnncccnncnnncnnnncnnncnnnncnnns 85 7 2 Accessing the presets library pop up from the controls button ooocccocccoccnncccnnccnnncnnncnnnncnnncnnnncnnns 86 TS N IAOW sets DIO urnas iii 87 e OUDE SVS pci la cdta 87 ios Patameten PASSINO ts ici 88 OS ACUSA ola 88 Els MA TO Up EE VICO io 89 O TOUS POD UD MER isc tos cli cas ta des curas tac dico tepa cas 89 7 9 Selec ng a groupn the Groups Pop Up MEA ua 89 8 1 signal Generator CONTON IN GOW td lio ds 90 8 2 Mes Weep Rartameter CUSTE santi 90 6 Wee mode radio DUON erreneren a islanaiisis 91 Ot WVinite NOISE RarametenCluster st da sas 91 80 IMG NOISE Pa e ect 92 G6 Oiantizatoniand DIMMER CONOS ita 92 A PP ics 2Gns ceumd eodentaldaehewacier cueate stone ueaieadeantmeusereausaretaseee 93 8 07 O NENTO niza ton CONOS e io odio 93 8 9 Selecting the Rectangular window from the FFT Window library oooccocccnocccocccnncnnnccnnncnnncnnoncnnns 93 610 PUTINS CONTO asii pao 94 8 11 1 second of 125 ms bursts every 1 4 of a second tina lata 94 8 12 1 second of 125 ms windowed bursts every 1 4 of a second cocoocccocccnncnnnccnnncnnncnnnncnnncnnncncnncnnnioos 94 8 13 Sena senerator conto lic ierra a E SS 95 DEPRE WNE CONTO VVINGOW mia 9
61. and SpectraFoo can emulate standard PPM ballistics but it can also do much more The ballistics for both the Peak crawlback and VU level is fully configurable The meter can show you the Peak RMS and VU levels along with holds for Peak and RMS simultaneously The meter also has two available color modes e The Level based color mode colors the meter bars based upon the the level of the signal The color breakpoints are user configurable and can be adjusted to provide smooth transitions or hard edges This mode is the standard configuration for the meters and is required to implement the K System calibrated meters 19 Instruments e The second color mode causes the meter bar to be color coded to indicate Peak and RMS and uses color to distinguish its different modes The yellow part of the meter indicates the instantaneous peak to peak level of the program material The purple part of the meter indicates the RMS level These colors are user definable The Peak and RMS meters each have independent resettable peak hold functions The peak holds are repre sented by triangular carets of the same color as the meter to which they correlate The hold indicators can also be drawn as bars The VU meter is an adjustable ballistic average indicator that is represented by the grey triangular carets or bar if selected Detailed meter readings 1 100 dB accuracy and meter control parameters can be accessed by clicking on the Show Details button The met
62. and VU meters w Clipped Sample Counter User Definable Over Digital Clip Counter The Level Meter counts consecutive full scale samples and displays the largest count encountered This is displayed in the field labeled cfs You can also define how many consecutive full scale samples the Level Meter has to see before it considers the signal to have clipped You control this behavior using the Physical Unit calibration system in SpectraFoo see Physical Unit Calibration In SpectraFoo The Level Meter has 20 Instruments a numerical counter which keeps track of the number of overs which have occurred This is displayed in the field labeled ent 63 de Figure 3 4 Over Counter The true flexibility of the meters is controlled using the Level Meter Controls window Click the Meter s pa rameter control button to display the Level Meter Controls window O Level Meter Controls Factory Default HH 2 Groups none ey gt Channel 1 57343 Di Key Channel 2 57343 Di Ft Meter Mode Straight Channels ey Chan 1 Chan 2 Y Peak Power 5 02 dey 4 24 dBy Y Peak RMS 14 33 dBy 11 63 dBy vi YU Avg RMS 17 66 dBu 15 60 dBy ST Reset Peak Holds Options Figure 3 5 Level Meter Controls Window Sum amp Difference Meter Mode The Level meters provide a Sum amp Difference mode that shows L R and L R metering When the Sum amp Difference mode is selected the left bar is the
63. annel The bright green trace provides instantaneous spectral analysis The purple trace shows the average spectral content referenced over a user specified length of time this is controlled from the Details window The dark green trace represents the peak spectral power monitored since the peak was last reset Using the Details window you can alter the Spectragraph s frequency and power scaling as well as its averaging characteristics in realtime This allows you to easily focus on very fine details In addition the Control window allows you to adjust the colors assigned to each trace Dual channel modes The Spectragraph can run as a 6 trace dual channel instrument allowing you to route any two channels to one Spectragraph window For example you could route the left and right channels of a stereo pair into a Spectragraph 26 Instruments 1 gt f 3 3 E f D i g I I t a i JE 4 f D be o e g 1 t a i Figure 3 9 Spectragraph showing the left and right channels of a stereo pair You can also route two different instruments such as a kick drum and a bass to a Spectragraph and do a live comparison between them To display a second trace in a Spectragraph 1 Select the two channels that you wish to display using the channel pop ups in the controls window 2 Select the mode of the second trace using the second traces pop up If the mode of the second trace is set to None the Spectragraph
64. ant to match the impedance characteristics of inputs and outputs e High impedance sources guitar bass keyboards should be plugged into a DI These are commonly called Hi Z e Low impedance sources microphones line level devices should be plugged into mic preamps or line level inputs These are commonly called Lo Z A metering standard developed by Bob Katz that establishes a baseline acoustic dB level and allowable headroom over the baseline A mathematic function where the input and output change at a constant rate For example the ratio setting on a compressor is a linear function if set to 2 1 for every 2 dB of input there will be 1 dB of output once over the threshold 4 db of input results in 2 dB of output etc 116 Lissajous Logarithmic O Octave Ohm Q Peak Phase Glossary Figure 184 A linear trace Named after Jules Antoine Lissajous this type of display shows coherence between two audio channels and can be used to display stereo position and or phase problems A mathematic function where the input and output change at a non constant rate For example the faders on a mixer are logarithmic they change the signal level a large amount with a small movement toward the bottom and a small amount with a large movement toward the top 12000 10000 8000 6000 4000 2000 A I 1 I I 1 1 1 L 1 1 4 6 8 10 Figure 185 A logarithmic trace
65. arrow pointing down the Power vs Frequency data panel is visible To hide the Power vs Frequency data panel set this control to undisclosed arrow pointing right Phase Ys Frequency Figure 4 7 Phase vs Frequency When Phase vs Frequency is set to disclosed the Phase vs Frequency data panel is visible To hide the Phase vs Frequency data panel set this control to undisclosed Figure 4 8 Instrument Enable This is the button with the IEC power symbol When this button is On filled with green the Transfer Function is running Figure 4 9 Solo button When the Solo button is On filled with red the Transfer Function is soloed Figure 4 10 Show Controls The Show Controls button is between Solo and Take Snapshot Clicking on this button opens the Transfer Function Control window The Transfer Function Control window provides all of the detailed controls used to adjust the display of the transfer function e lt control gt clicking this button pops up a menu that allows you to select the Source channel for the Transfer Function e lt option gt clicking this button pops up a menu that allows you to select the Response channel for the Transfer Function e lt command gt clicking or clicking and holding this button pops up the parameter library menu for the Transfer Function Take Snapshot Figure 4 11 Take Snapshot Clicking on Take Snapshot takes a snaps
66. ased punches can be used to capture individual drum beats in a hands free way allowing you to devote your attention to placing the mic while still benefiting from SpectraFoo s analysis 97 Capture and Storage O Capture Control Mode Envelope 2 Avail Time 01 39 51 004081 Pre trig time 00 09 Trig Lvi 1 9 dB BOR Post trig time 01 15 Detrig Lwk 14 0 dB 20 Post detrig time 01 06 O auto arm W zabie stop Recora Figure 10 2 Level based Capture Mode There are three handles within the Trigger Envelope area e The left handle lets you set the trigger level and the pre trigger time When the input signal exceeds the trigger level the system starts the recording from the trigger time minus the pre trigger time This ensures that you will not miss any of the initial transients in the material you are trying to capture e The center handle lets you set the de trigger level and the post de trigger time This allows you to specify the amount of time that SpectraFoo will continue recording before checking the signal level to determine if it is below the de trigger level The vertical position of the handle sets the de trigger level and the horizontal position sets the post de trigger time e The right handle allows you to set the length of time that the signal must remain below the de trigger level to cause the system to stop recording The Trig Lvl field indicates the level threshold that will trigger the recording
67. between the source and response as function of frequency This allows you to measure the properties of audio processing systems including systems that contain acoustic elements You can determine the amplitude and phase response of an equalizer in the presence of a musical signal as easily as measuring the sound coloration of an acoustic space The transfer function really only makes sense when the source signal is the input to some audio processing arrangement and the response signal is the measured output of the system lt does not generally make sense if the the source and response are truly unrelated as in the case of the two channels of a stereo mix in this case meaning a multi track mix with panned elements as opposed to a true stereo program such as an X Y recording Even in the case of a stereo mix the transfer function may provide some information about the spectral balance of the recording but in general the spectral balance is not constant in time Even when the source and response signals are related they usually will not be time aligned For example if you are measuring the room response of an auditorium there will be the speed of sound acoustic delay between the source signal and the response signal received at the measurement microphone In order to properly measure the power and phase of the response signal relative to the source signal the source signal must be delayed to time align it with the response signal 55
68. bility M Enable Solo M Window Positions Mi instr Channel Routing vi Instrument Params vi Control Windows Mi Global Preferences M FFT Analyzer Depth Cancel h Ra 3232 Figure 7 3 Window Sets Dialog 4 Name the Window Set then press the lt tab gt key 5 Choose a key command to recall the Window Set This can be any key or group of keys you like Be aware the software will allow you to set any key or command key combination as the key command Don t set a command that you would really like to use otherwise like A or lt space gt 6 Select the attributes of the instrument configuration that you want to recall using the checkboxes and click OK The snapshot will automatically save all information You can now recall the window set with the command key you specified To change what parameters are recalled after a window set has been created 1 Select the window set that you would like to modify from the Sets menu or type its command key 2 Choose Rename Current Window Set from the Sets menu A window set dialog will appear 3 Select which types of parameters you want to be recalled You can also change the name of the window set and the command key at this time Click OK to save your changes Link Groups SpectraFoo provides a flexible linking system to allow you to keep all of the parameters associated with a group of instruments linked You can use this feature to link the settings of a stereo pair
69. bration in SpectraFoo 29 Instruments Trace colors The traces in the Spectragraph can be set to any color supported by your Mac To change the color of a trace in the Spectragraph 1 Click on the colored well to the left of the trace visibility check box in the Spectragraph Controls window Show Traces 1 Peak lM Awg lM 1 Instant E 2 Peak E 2 Avg E 2 instant Figure 3 16 Accessing Trace Color controls The Macintosh Color Picker will appear OGA Colors a O s E Al Hs Figure 3 17 The Mac OS color picker 2 Choose the color you want and click OK The trace will now appear in the color you selected Octave Analysis The Spectragraph includes octave modes which allow you to display frequency data in resolutions ranging from 1 octave to Continuous You use the Resolution pop up in the Spectragraph Controls window to set the display resolution 30 Instruments O Spectrag raph Controls n Factory Default Hg Groups 1 HH Channel 1 57343 Digi H Channel Z FA H9 i Second Traces Channel 2 H Use dBu Calib Accumulation Mode White Noise is Flat HA Resolution 1 Octave 3 Reset Peak Holds Show Trace 2 Octave io iF 1 3 Octave f A 1 instant im oF 1 6 Octave l E 2 Instant 1 12 Octave kyg Mode Log 1 24 Octave Settling Tine 7 357 s F i F Scali rd Continuous oe eng rior a T 16 10 kHz ee ae a a a ITIITI 81631 62 125 25
70. button Figure 2 1 Power button e Asolo button Figure 2 2 Solo button e A parameter control button Figure 2 3 Parameter control button The power button when turned off disables the instrument The solo button works much like the solo button on a recording console in that it shuts off all of the other instruments However if more than one instrument is in solo mode all of the soloed instruments will continue to run while the un soloed instruments will be disabled If an instrument is in solo mode and turned off it will be disabled as will all of the un soloed instruments These controls are provided to allow you to focus your attention on measurements made by a subset of SpectraFoo s instruments Although SpectraFoo is always analyzing the signal in real time limitations in the drawing speed of the host computer can cause the display to slow down when many instruments are enabled By soloing the instruments that you are specifically interested in at a given point in time you will improve real time performance of the display For faster host machines the difference in graphics performance will be less noticeable When the parameter control button is clicked it opens a floating window which allows you to control in real time many of the display parameters for the instrument in question These control windows will be described in more detail below Some of the instruments have additional controls when they are in the consolidate
71. capture the display can function as a nifty storage oscilloscope most storage scopes are not capable of playback The Details readout shows the percentage of amplitude referenced to full scale e Power Balance The Power Balance ribbon is an overview history of the left right power balance meter Drag the cursor along the ribbon and the Details readout will track the amount that the power in one channel exceeds the other as a percentage of the sum of the total power in both channels 101 Capture and Storage e Power History The Power History ribbon is an overview history of the PPM and RMS meters The Details readout will track the Peak and RMS levels for the part of the display which lies under the cursor Spectral History The Spectral History ribbon is an overview history of the Spectragram This display is incredibly effective at revealing minute details of musical and sonic structure When you hold down the option key and click the mouse in the ribbon a marker will appear to the right of the frequency calibration giving a rough indication of the frequency of the spectral feature you are pointing at with the mouse pointer The Details readout will track the precise frequency range of the display feature you are pointing at If you hold down the Option key while clicking on a spectral feature in the ribbon the Details readout will display the precise frequency range that the selected feature occupies Correlation This display shows the phas
72. ces of the associated snapshot are inverted in the transfer function window lt option gt clicking this check box will set the state of all of the snapshots in the list 6 The Fade pop up menu controls how the associated traces are faded in the transfer function window lt option gt selecting an item from this menu sets the state of all of the snapshots in the list The Overlay List window also has a mini menu window command pop down menu in the upper right hand corner above the scrollbar 74 The Transfer Function Figure 4 35 Mini menu window command pop down menu This menu provides the following commands e Save Selected Snapshots Select this command to save each of the selected snapshots to disk e Load Snapshot Select this command to load a snapshot file from disk e Remove Selected Snapshots Select this command to remove the selected snapshots from the list e Average Selected Snapshots Select this command to create a new snapshot from the average of all of the selected snapshots You can choose to weight the average with the coherence of the measurements If you make a number of measurements with different mic positions and create a weighted average you can remove the effects of local nulls and generate a more accurate measurement of the response of the system e Smooth All Snapshots Select this command to smooth all the snapshots in the list e Unsmooth All Snapshots Select this command to unsmooth
73. coding for Peak and RMS lev els Use PPM Ballistics checkbox Activates PPM decay for the meter If this is unchecked the meter will use the original instanta neous SpectraFoo ballistics 22 Instruments Draw VU as Solid Bar When unchecked the white tick shows the VU lev el and RMS is shown as the solid bar in the meter When checked the solid bar shows the VU level and the white tick shows RMS This allows you to create a bar meter which uses VU ballistics Use AES Std RMS Ref When checked this will adjust the RMS level by 3 01 dB to match the AES recommended specifica tion Regardless of how this parameter is set it must be set before calibrating your analyzer Draw Peak Level as Bar checkbox When checked the Level Meter will display the Peak and RMS levels as one continuous bar as in previous versions of SpectraFoo When unchecked the Peak level will be displayed as a separate indicator which floats above the RMS bar Useful for creating meters that read peak only Draw Holds as Arrows checkbox When checked Peak holds will be displayed as ar rows like previous versions of SpectraFoo When unchecked Peak Holds will be displayed as lines Auto Release Holds checkbox When checked the Peak Holds will reset after the amount of time you specify using the PPM Hold Re lease Time slider Use Solid Color Transitions When checked the meters will show a hard tran sition from one color to the next this i
74. ctraFoo is the first audio visualization system to provide high reso lution spectral and phase information that is fluidly animated and absolutely synchronized to the live audio signal It is the first audio analyzer anywhere to allow the user to tap into the power of synesthesia Like many other audio analyzers SpectraFoo s analysis engine is based on the Fast Fourier Transform FFT The FFT algorithm is an efficient means of computing a Fourier Transform on a computer The Fourier transform was developed between 1804 1807 by the mathematician Joseph Fourier as part of a study of heat transfer The Fourier transform converts a continuous record of amplitude vs time into a record of amplitude vs frequency A modification of the Fourier Transform called the Discrete Fourier Transform DFT was developed to deal with sampled rather than continuous waveforms The FFT algorithm was developed as an efficient way of computing the DFT on digital computers FFT based analysis facilitates highly precise measurements As a result it has become a natural choice for audio analysis systems Unfortunately FFT based methods have historically been more suited to Electrical Engineering type audio measurements than dynamic measurements of musical program material A traditional technique is to subject the system being measured to a known controlled test signal In order to get high resolution measurements from the analyzer one must wait for a significant period o
75. d are O at the bottom of the graph and 1 at the top of the graph These limits do not change when you change the power limits Figure 4 15 Phase Panel The phase panel shows the relative phase between the response and source signals The vertical scale of the phase panel is linear and is in units of degrees Since phase is cyclic that is if the phase of a signal is x then x 360 is the same phase the phase curve can wrap around from 180 to 180 You can see this in the graph above at f 2kHz The phase does not really have a discontinuity at 2kHz it has just wrapped around to 180 The horizontal calibration is in units of frequency Hz The limits of the horizontal scale are controlled with the transfer function control window Understanding the Transfer Function The purpose of the transfer function measurement is to allow you to find out what a particular electro acoustical system is doing to the signal it is processing We call the system being measured the System Under Test SUT also called DUT in other literature The SUT could be as simple as an equalizer or as complex as a multi zone 62 The Transfer Function sound reproduction system coupled with a measurement microphone or many measurement microphones for that matter The key thing to understand is that every system changes the signal that runs through it An example of a simple measurement is finding the transfer function of a parametric equalize
76. d Real Time Rack window These controls provide hardwired linking functionality for the instruments The controls for the real time rack instruments are illustrated and described in the picture below 14 SpectraFoo Basics Stereo Link Allows you to link the parameters settings for the left and right channels of a particular instrument Show Details Indicates that the instrument has adjustable display parameters and or detailed numeri cal readings Clicking this button will bring up a window that will display these items Link Allows you to link the display parameters of the Spectragraph and Spectragram for a given channel Power Button turns an instrument on and off Solo Shuts off all other instruments Figure 2 4 Real Time Rack Control buttons Common Features Control Windows As with the instruments themselves the control windows for the instruments also contain some common features e The control window for each instrument contains one or more Active Channel pop up menus These allow you to select which analyzer channel is routed into the instrument for display for instruments that only meter one channel at at time For stereo instruments there will be more than one Active Channel pop up menu one for each channel that can be routed into the instrument and generally labelled Channel 1 and Channel 2 O spectragram Cont Factory Default ray Groups Active Channel Frequene ULN 2 R P
77. dow is not visible show the Control window by clicking the Show Controls button 2 Select the desired Lissajous mode Vectorscope X Y or Stereo Position from the Scope Mode pop up menu Adjustable sensitivity The sensitivity of the meter can be adjusted using the Sensitivity slider in the Lissajous Control window The sensitivity can be increased to make the phase of low level signals visible 46 Instruments Auto Sensitivity Mode Often the dynamic range of the signals being monitored is quite large When the dynamic range is large no one setting of the sensitivity is correct to show all of the details of the phase of the signal Sometimes the sensitivity is too small and the lissajous trace looks like a single dot Other times the sensitivity is too large and the trace extends way past the edge of the meter Auto Sensitivity mode automatically calculates the appropriate sensitivity setting for the meter at each instant of time It is activated by checking the Auto Sensitivity button in the Lissajous Control window Hi Res Mode To increase the speed of display the Lissajous scope computes its display from every fourth sample This gives a reasonably accurate representation of the phase information It also generates a display that is not quite as smooth and clean as an analog scope The Lissajous Hi Res Mode makes the Lissajous scope compute its display from every sample This mode is activated by checking the Hi Res Mode button in
78. ds to averaging the level in decibels An average computed this way would be for example 1 dB 2 dB 2 1 5 dB While this is not mathematically correct and appears to over represent the contribution of low level signals it is still useful as a measurement tool The second mode which corresponds to SpectraFoo s Lin Averaging Mode and is mathematically correct averages the actual power level and then takes the logarithm of the average to give the level in dB This give the true average level of the signal but does not correspond to the expected visual average With this averaging mode 1 dB 2 dB 2 1 5144 dB which is mathematically correct This difference is not trivial Consider the average of 10 dB and 40 dB The Log average is 10 dB 40 dB 2 25 dB The linear average is 10 dB 40 dB 2 15 75 dB As stated the Log average over weights low level signals Log Averaging is more useful for showing overall spectral balance in the monitored material This is probably because the human ear over weights low level signals in much the same way that Log averaging does For building EQ curves linear averaging makes the same average measurement as what an EQ will see Not surprisingly we have found the Linear Averaging mode works better when attempting to capture spectral templates of material for matching purposes Spectral Snapshots Overlays amp Libraries You can use the Spectragraph to create spectral snapshots and save them
79. e Left Channel Spectragram Right Channel Spectragram Left Channel Spectragraph Right Channel Spectragraph Left Channel Power History Meter Right Channel Envelope History Left Channel Envelope Display Right Channel Power History Meter Figure 2 7 Real Time Rack Real Time Rack Consolidated View You may move instruments within the rack by clicking on the instrument you want to move and dragging it to a new location As you drag the instrument around the rack will indicate places to which the instrument can be moved by drawing a heavy border around the empty spot If you release the mouse button while the instrument is over a location that is already occupied the instrument will automatically return to its original location Moving an instrument within the rack does not interrupt the analysis process or even the display update In fact whenever you turn a knob or move a fader in SpectraFoo everything responds instantaneously 17 3 Instruments SpectraFoo Standard SpectraFoo Standard includes the following set of real time metering instruments e Level Meters high resolution standards based level metering with the ability to display Peak RMS and VU levels simultaneously Supports European and AES PPM standards and K System metering Highly user configurable e Spectragraph ultra high resolution real time two channel spectrum analyzer with snapshots cursors and overlays Supports a variety of scaling spectral weighting and bal
80. e indicated number of degrees The parameter controls for the Transfer Function are accessible from within the Controls window of the Transfer Function This is consistent with the operation of all other SpectraFoo instruments The Transfer Function Controls window is accessed by clicking on the show details button in the Transfer Function window or in the Master Controls window In addition the Transfer Function now has a solo button and an on off button Transfer Function Controls You control the display and behavior of the transfer function window with the Transfer Function Controls window 58 The Transfer Function A Transfer Function Controls source Internal 1 ES Response Internal 2 hey Resolution Continuous E Frequency Range 6 Hz 22 05 kHz ft al eo aK Fl lh o ap P md cl Ll Pn ne A Pl 816 31 62 123 250 500 ik k dk Sk d k Power Range 40 006 40 00dE EEE EE IET E EEE EE i 40 32 24 Ab 4 0 amp 16 4 32 40 dls al Scaling Arg Rate Arg Power Cutoff Display Instantaneous Show Octave Details Fade Coherence EB Compute Delay Figure 4 5 Transfer Function Controls window Source pop up menu You use this menu to select the source channel Response pop up menu You use this menu to select the response channel Resolution pop up menu You use this menu to select the octave resolution of the analysis You can select from 1 Octave power is displayed as bars each band is one octave wide 1
81. e Capture button will transform the impulse into a capture that can be analyzed using SpectraFoo s other instruments Analyzing captures is covered in the Capture and Storage section e The Rename Window button will allow you to give the impulse a unique name This is useful when taking multiple measurements to compare e The magnifying glass buttons will zoom in and out of the timescale as will the small window scrollbar 57 The Transfer Function ane TransTor Finiti Par E Erie MH Jl aI yo TE Lar E 7H a au 1 i ee ee format ar Car bere Figure 4 4 Transfer Function after the measurement has been time aligned e The Power vs Frequency graph shows the amplitude difference between the source and response signals as a function of frequency A trace oriented on the zero line indicates that the source and response signals are the same For the frequencies where the trace is above zero the response signal has more power than the source For the frequencies where the trace is below zero the response has less power than the source e The Phase vs Frequency graph shows the relative phase of the source and response signals as a function of frequency A trace oriented on the zero line indicates that the signals are in phase For frequencies where the trace is above zero the source is delayed from the response by the indicated number of degrees For frequencies where the trace is below zero the response is delayed from the source by th
82. e correlation between the capture channels The Details readout shows the correlation on a scale from from 1 to 1 at the cursor 00 00 39 716875 Ribbons Envelope Power Balance Power History Spectral History Correlation History 00 00 54 071041 Window Start Window End Ee Figure 10 10 Capture Overview Window Bottom e Window Start End time fields These display the time window of audio that is currently displayed Ribbon This pop up menu allows you to select which ribbons will be displayed in the Capture Overview Window Selecting an item in the ribbons pop up menu toggles it on and off If you hold down the option key and select a ribbon all other ribbons will be hidden This allows you to utilize the entire Capture Overview Window to view a particular ribbon a Figure 10 11 Stop Click this button to stop playback Figure 10 12 Play Clicking this button causes the capture to start playing from wherever the cursor is in the ribbon Figure 10 13 Play From Beginning Clicking this button causes the capture to play from the beginning Figure 10 14 Playback mode This button cycles through the different playback modes which are Figure 10 15 Play Forward Figure 10 16 Play Backward Figure 10 17 Loop Back and Forth ER Figure 10 18 Loop H Figure 10 19 Play Once Between Loop Points 102 Capture and Storage aj Figure 10 20 Zoom Out Clicking this button causes the capt
83. e for the difference between the suggested retail price of SpectraFoo Standard and SpectraFoo Complete at the time of the upgrade Contact Metric Halo directly at lt sales mhlabs com gt for more information Introduction Welcome to the SpectraFoo Visual Audio Monitoring System the world s first audio analysis environment that actually lets you see music SpectraFoo is a high precision low latency fully realtime audio visualization and analysis system SpectraFoo takes advantage of the phenomenon known as synesthesia The word synesthesia meaning joined sensation denotes the rare capacity to see sounds taste shapes or experience other equally startling sensory blendings whose quality seems difficult for most of us to imagine Very few people experience natural synes thesia Those who do usually possess distinct cognitive advantages over the rest of us For example many people with perfect pitch associate particular pitches with particular colors They see sound as well as hear it The interaction of vision and hearing helps these people maintain an absolute point of reference with regard to pitch This allows them to discern absolute pitch values without the need for a reference tone SpectraFoo allows anyone to experience the benefits of synesthetic sensation 11 Introduction In order for the human brain to properly integrate multiple sensory inputs and derive greater value from them the inputs must be truly synchronized Spe
84. eate an average snapshot from a number of Spectral Snapshots 1 If the Spectral Snapshots List is not visible choose Show Spectral Snapshots Window from the Window menu 2 Select the snapshots you want to include in the average PLO A Spectral Snapshot List a Snapshot Name Show In Lal O 1 LE Lefti E 1 LE Lefti El LE Drums 1 Left arg Z LeftiRight O LB Drums 1 Right avg 2 LeftiRight Figure 3 30 Selection for Snapshot Averaging 3 Choose Average Selected Snapshots from the Spectral Snapshots mini menu ODO Spectral Snapshot List Snapshot Name Show In 1 LB Left 1 LB Left El LB Drums 1 Left avg _2 LeftiRight 0 LB Drums 1 Right avg _2 LeftiRight Save Selected Snapshots Load Snapshot Remove Selected Snapshots Average Selected Snapshots Create Transfer Function Y Ask About Unsaved Snapshots Export Selected Snapshots Y Export as 1 3 Octave O Figure 3 31 The Spectral Snapshots mini menu 4 The Average Snapshots dialog will appear Average made Wed Aug 17 2005 11 36 33 AM Comments Average of int Mic Drums 1 Lavg int Mic Drums 1 Ravg Figure 3 32 Average Snapshots Dialog 5 Name the average and type any comments you might have By default SpectraFoo places the names of the Snapshots that you are averaging in the comments field Click OK when you are ready to save the average The new Average will appear in the S
85. ectively 24 Instruments To change the Level based Colors 1 If the Meter s Control window is not visible show the Control window by clicking the Show Controls button and then selecting the Options button at the bottom of the Controls window 2 Click the appropriate color tile within the Controls Window The Macintosh Color Picker dialog will appear The three Level based color tiles correspond to the Safe color the Caution color and the Danger color respectively These colors also correspond to low medium and high levels The stan dard configuration of these colors is Safe Green Caution Yellow Danger Red Meter bar color transition levels The level based color coding scheme assigns colors to the meter bars based on the corresponding level of the signal at each point along the bar The colors are taken from the level based colors as described above The transition points e g levels at which the color changes from Safe to Caution and from Caution to Danger are user selectable This allows you to set the points at which the color bar changes to match your needs and expectations To change the transition levels 1 If the Meter s Control window is not visible show the Control window by clicking the Show Controls button and then select the Options button 2 Adjust the appropriate Level Slider in the bottom of the control window 3 The Danger level slider controls the level at which the met
86. efault 4 Groups none HA Channel 1 left HH Channel 2 right hey Power Threshold a anar S832 76 0 4 58 2 46 40 34 25 22 16 10 oles 00 Ik ek dk Sk kHz Figure 3 54 Phase Torch Control window In the past the display in the Phase Torch had an infinite dynamic range This was useful for some applications e g looking at phase dispersion in noise and dither and detecting dither in processes when there is no signal present Unfortunately it could also make the Phase Torch difficult to interpret The Power Threshold slider allows you to limit the dynamic range of the instrument Only the phase points with a RMS power level that is greater than the specified threshold are displayed Figure 3 55 Phase Torch with threshold at 60 dB 48 Instruments Figure 3 56 Phase Torch Full Range Band Power History This instrument allows you to see the history of the amount of power in a specified band of the spectrum The instrument s details window allows you to set the center frequency and the bandwidth of the power band that you are interested in monitoring The preset values for this instrument are 1 12 of an octave at 6kHz This allows it to function as a very effective sibilance meter Figure 3 57 Band Power History Band Power History Controis Factory Default 43 Groups none HH Channel 1 57343 Di 4 Center Frequency 6 kHz Width 1112 05 Octave Figure 3 58 Band Power History controls
87. eft and right channels are predominantly out of polarity commonly referred to as out of phase or mono incompatible Stereo Position mode In addition to the X Y and Vectorscope modes SpectraFoo has a Stereo Position mode This mode displays each of the relative phase vectors in the signal The length of each phase vector is log scaled Vectors pointing along the L 45 line are mono sources that are panned to input channel 1 Vectors pointing along the R 45 line are mono sources that are panned to input channel 2 Vectors within the L R 90 cone correspond to normal substantially in phase program material Vectors that are outside the L R 90 cone correspond to program material that is more or less out of phase Under normal mono compatible signal conditions the vectors will be generally within the in phase cone and there will be occasional short vectors that appear within the out of phase region If the signal is substantially out of phase or not mono compatible the majority of the vectors will appear in the out of phase region Figure 3 51 Lissajous in Stereo Position Mode O Lissajous Controls Factory Default hey Groups none HA Channel 1 left H Channel 2 right e E Lissajous Color Sensitivity A 2 1x 2x dx ox 1bx 32x bs Yectorscope E f Auto Sensitivity S T iia wi High Resolution Figure 3 52 Lissajous Control window To change the Lissajous mode 1 If the Lissajous Scope s Control win
88. enu The following dialog will appear 1107 Jaw A Full Scale Sample is detected within LSB of digital full scale A clip is 3 consecutive full scale samples Digital full scale 0 dBFS is Cancel 0 Figure 6 1 Level Calibration Dialog 2 Enter the number of dBu or dBV that is output by your system s D A when it is driven by a full scale signal This setting can also be determined by using the Signal Generator to generate a O dB 1kHz sine wave Run the signal out to your analog console or other hardware that will act as your studio calibration standard Note the meter level on your calibration standard this should be a peak reading meter That is the value to enter into the Calibration dialog in the dBu field Level calibrations will now match your calibration standard The level calibration dialog also allows you to define what is considered a clip 1 A clip is defined as a certain number of consecutive full scale samples You can specify the number of full scale samples in the calibration dialog When the system detects the specified number of full scale samples in a row it will register a clip 2 A full scale sample is defined as a sample that is within the specified number of Least Significant Bits LSB of digital full scale Dither can confuse a clip detection algorithm that only looks for full scale samples This parameter allows you to specify a margin of error 2 3 LSBs generally works well 04
89. er also contains a numerical counter that indicates the largest number of consecutive samples surpassing O dBFS as well as the number of times the input signal has exceeded the clip threshold The calibration of the meters is referenced against O dBFS unless you have selected one of the dBu calibrated meter scales These provide instantaneous numerical readings of the Peak RMS and VU levels with 0 01 dB accuracy Click this button to pop up the Power Meter Details window ui doo CEE Solo der CEE a Level Meter Controls Channel 1 57343 Di 5 Channel 2 57343 Di 5 Chan 1 Chan 2 cd Peak Power 4 15 dBu 9 98 dBu 16 65 dBu 20 67 dBu YU Avg RMS 19 70 dBu Clicking this button resets the Peak and RMS Peak Holds Click this button to pop up the Power Meter Options window O Level Meter Options YU Settling Time 0 203 PFPH Settling Time 1 705 Yu PPH Peak Float Size 4 Hold Release Time 2 005 Meter Scaling Tick Spacing 3 00dE Scale Type SpectraFoo HH w Use Level Based Color Ww Draw Peak Level as Bar M Use PPM ballistics E Draw Holds as Arrows Draw YU as Solid Bar wi Auto Release Holds Use AES Std RMS Ref Use Solid Color Transitions Safe Until 20 00 dBFS BS Saag NTT action ae re on no O pagar TTT TTT T 70 6d rest 00 dBES e 2832 26 70 6d 58 32 46 40 34 28 El Pear res Ol vu Figure 3 3 Digital Level Meters Peak RMS
90. er bar is completely at the Danger color 4 The Caution level slider controls the level at which the meter bar is completely set to the Caution color 5 The Safe Until level slider controls the level below which the meter bar is completely set to the Safe color The meter bar is displayed in the Safe color from o to the Safe Until level Spectragraph Overview The spectrum analysis within SpectraFoo utilizes a multichannel high resolution real time FFT engine At its highest resolution setting SpectraFoo utilizes 64k point FFTs allowing you to see features with widths as small as 2 3 Hz SpectraFoo creates a new analysis up to 60 times per second allowing you to see musical structure even at the highest tempos Although the Spectragraph excels at traditional applications such as analyzing the distortion characteristics of audio equipment its true strength lies in its sheer speed SpectraFoo s Spectragraph is fast enough to create a highly detailed animated movie of sonic events If you have been watching SpectraFoo monitor a favorite album of yours while reading this guide you probably have already noticed this Because the Spectragraph is so completely synchronized with the material it is monitoring the information it displays can be experienced in a sensory rather than intellectual way much the same way as you experience music itself The key to making the most out of the Spectragraph as well as all of the other instruments is
91. er controls the vertical offset of the trace zero line The HOffset slider controls the horizontal offset of the trace trigger point The Illumination slider controls the brightness of the grid Sliding it all the way to the left shuts off the grid as well as the grid details readout on the scope The Oscilloscope has been enhanced to provide two input channels This allows you to show two different channels on the scope at the same time Sida Digita 1 44 0 being Ayes oe TARF Figure 3 44 Oscilloscope running in dual trace mode Single and Dual channel modes The Oscilloscope supports two input channels and a variety of second trace modes The second channel mode is selected using the Mode pop up menu in the Oscilloscope Controls window an Oscilloscope Controls Factory Default he Groups none E Channel 1 57343 Di HA Channel 2 57343 Di 2 Single Trace Only Dual Trace Subtract Second Channel mebase a Add Second Channel LI Multiply Second Channel E A Slope 1 Trigger Level Y Se THT Tp o o EN EE w Retrig Time 0 m i Arm Trigger Trig Chan m gt Grid Figure 3 45 Oscilloscope Controls window Trace display modes Five different modes are provided 1 Single Trace Only The scope runs in the original single trace mode The trace corresponds to the signal in the first input channel 43 Instruments 2 Dual Trace Two traces one corresponding to each of the input c
92. ey Command editor Set Key Command Close Front Floating Window e LW Cancel Figure 11 3 Key Commands editor With the editor open enter the key command you want to assign to this function and click OK 107 Quick Menu Reference Analyzer The Analyzer Menu allows you to change the resolution of the Analyzer Although you can switch the reso lution of the analyzer to less than 4096 points SpectraFoo is so fast that we can t see why you would want to if the computer you are using is especially slow or if it does not have any cache you may want to lower the analyzer resolution in order to gain some speed at the expense of frequency resolution You can also use this menu to increase the resolution of the analyzer The 8192pt setting is a good compromise between speed and resolution on fast machines The Remove DC Offset command allows you to remove any residual DC offset from the input converters If the Spectragraph shows a hump at 0 Hz even with no input signal present mute the input to SpectraFoo and select the Remove DC Offset command to remove the DC offset from the input The Reset Analyzer command causes the analyzer to disconnect and the reconnect itself from the selected input hardware It can be used if the system appears to be behaving strangely No instrument updates or severe digital distortion The Level Calibration command allows you to set a reference value for Digital Full Scale 0 dBFS This wind
93. f phase monitoring tools including a lissajous phase scope correlation metering and the unique Phase Torch It does not provide any of the deeper analysis tools found in SpectraFoo Complete SpectraFoo Complete provides all of the metering tools included in SpectraFoo Standard but also includes a number of additional features that allow more detailed analysis of audio signals and systems SpectraFoo Complete adds a multitone high resolution sweeping signal generator a recording capture and static analysis system high resolution bit level metering facilities and a detailed two channel FFT transfer function measure ment system with support for Music Based Measurement Time Delay Spectroscopy and multiple overlays with coherence based averaging SpectraFoo Complete is a critical tool if you will be doing acoustical mea surements sound system or monitor tuning musical instrument measurements mastering or any type of me tering or measurement in which you need to be able to capture and strore the signals that you are measuring This manual documents both configurations of SpectraFoo Standard and Complete Features that are only present in SpectraFoo Complete are notated with SFC at the beginning of the section that documents the feature Metric Halo has a no penalty upgrade policy for all software products If you have purchased SpectraFoo Standard and later decide that you need the power offered by SpectraFoo Complete you can upgrad
94. f time while the output of the system is captured by the analyzer and then transformed If you want to measure the average response of the system you have to wait for the analyzer to make many captures transform them and average them before you see the results With traditional transformation algorithms the rate at which the signal is transformed is constrained by the spacing of the spectral lines As a result many professionals who work in the creative side of audio have resorted to using low resolution RTA type analyzers to get real time information SpectraFoo utilizes patent pending technology to decouple the transformation resolution from the transformation rate As a result Spec traFoo is fast fast fast It can perform multichannel FFTs up to 60 times a second allowing you to see spectral features as small as 2 3 Hz wide while staying absolutely synchronized with the source material This allows you to experience and analyze sonic events simultaneously In addition to its unmatched realtime performance SpectraFoo also provides a full suite of highly precise quantitative analysis tools including a capture and storage system which is seamlessly integrated into the monitoring environment All of the intuitive knowledge you have gained via synesthesia can be leveraged on top of the quantitative measurements that SpectraFoo provides The following is a guide that provides an overview of SpectraFoo s features and capabilities This guide assu
95. ffsets inm the Bit IMSS ii 51 200 VISUAL sor Me DE MAT pidas 51 3 06 Instantaneous Snapshot OF BICMALUIX sitial artos ds 52 2 67 ACCUMUALION Snapshot OL BIAIMAUIN Borda 52 3 68 Bit Scope Layout with 512 Sample Time Slice and 8 Columns 0occcocccnnccnnccnnncnnnccnnncnnnccnnncnnncnnnnss 53 3 09 BIE LayGuUt IN Bil SCONE art lit 53 SO WEY INACLCY it to 53 o o A a a a a a a 54 4 1 SpectraFoo Signal Arrangement for MBM Transfer Function cccoocccnccnnccnnncnnnccnnncnnnncnoncnnncnnnncnnncoss 55 4 2 Transfer Function of a Room Response with a time delay occooccconccnncccoccnnncnnnncnnncnnncccnncnnnonnnnss 56 4 3 Time Aligning the measurement with the Delay Finder Window oocccoocccoccconccnnccnnncnnncnnnncnoninnnoss 57 4 4 Transfer Function after the measurement has been time aligned oocccocccoccccncccnncnnncnnnncnnncnnonennninos 58 A De Tanier FUNGCHON CORUOIS WINDOW ie 59 AO NOW Er VS FICOUCIOY arca 60 Aas PASE VS WLCCUCI CVA srra a E E 61 2 Oe MSHI O hiked uence candtent data tera tata eres lave T nea 61 ZAI O o A a terre ee re EE ee reer 61 AO SILOM C ORI ONS astas 61 Asi les dro OMNIS MOL Gcicerarta sateen stu icesetts asteouaacecadatadaeauie E a E erate euesuadts 61 BAD MOVER O 61 O EAE ete ine rere eet Peete E E eer rae en ee ameter eee es ere 62 AA POWER TANI iaa 62 A A A 62 AO MIS Measurement seta asalta data leas 63 e a your DAD ChaT arree A canines 64 AOS NCOUSUC TES US CCU ari ogni 64 4 19 Transfer func
96. for all times This means that the time between Time 0 and the first before the impulse has propagated through the system spike in the impulse response is the delay between the being tested source and the response signals If you move the cursor of the delay finder to the first spike you will delay the source signal by the appropriate amount to time align the source and response signals ADO Delay Finder In 2 R In 1 Tuesday April 5 2011 2 24 49 PM ET i l ral i a jla pr Ea Maximum Channel Delay 192000 samples 4353 742 4919 73 ft 1481 82 ml Make Capture Source Channel Delay 111 samples 2 517 ms 2 34 36 m ethene 4 nu y T E O IE E A A P _ LIF Cursor All of the other spikes present in the impulse response are the time delays of the various reflections in the system These can be real reflections from walls tables etc or they could be virtual reflections from the digital delays in a reverb algorithm or electrical reflections due to improperly terminated studio wiring Figure 4 3 Time Aligning the measurement with the Delay Finder Window e The delay readouts provide precise information about the relative delay between the left and right chan nels for the current cursor position This information is provided in samples milliseconds and in feet assuming standard temperature humidity and pressure The maximum inter channel delay supported by SpectraFoo is about 750 milliseconds e The Mak
97. g SpectraFoo it is possible to make measurements of subtle sonic effects while you are experiencing them This quickly leads to a deep understanding of how to achieve a sound and how to fix problems when they occur While we have touched on a number of possible applications we expect that you will think of many others In fact like the makers of any good tool we expect to be amazed and astounded by some of the things that you accomplish with SpectraFoo In its current implementation SpectraFoo is not intended to be a replacement for specialized audio component test equipment such as Audio Precision However using SpectraFoo in conjunction with such equipment will increase the scope of the analysis which can be performed on audio systems SpectraFoo can be used to to make dynamic electrical engineering measurements which are difficult or impossible to make with other analyzers due to their inherent speed limitations An example of such a measurement is measuring the distortion characteristics introduced by the manipulation of dynamic analog circuit elements such as potentiometers or by the manipulation of the parameters of a DSP algorithm eg moving a fader on a digital console SpectraFoo s greatest strength lies in its ability to provide quantitative measurements which can be syn chronously referenced against the subjective experience This is the Foo factor It is a widely held belief in audio circles that good specs and performance
98. g the enable and solo states of the instruments in the rack You can set up predefined groups of enabled instruments using the commands found in the group menu This allows you to quickly and easily switch modes as far as where your attention is focussed These instrument groups only effect instruments in the consolidated Real Time Rack view described below Even though these are called Instrument Groups they have no connection to the Link Groups described above A Sets Window Add to Group Library Delete from Group Library All On All Off Spectral Monitoring Phase and Balance Histories Time and Meters Figure 2 6 Instrument Groups Menu Only applies to instruments in the Real Time Rack e Add to Group Library Takes a snapshot of all of the current settings of the power and solo buttons A dialog box will appear allowing you to name the group When you name the configuration you may use the slash key followed by the character of your choice to create a command key to recall the group For example you have a group you want to name My Scene If you type My Scene 0 as the name you may recall this configuration by pressing Command 0 e Delete from Group Library Deletes a group from the menu A dialog box will appear with a pop up menu that contains all of your currently saved groups Select the group that you wish to delete from the menu Click OK to delete click cancel to abort the delete operation e Grou
99. ggers on either polarity and either slope Timed Polarity Check rearms after the desired retrigger time Clip Capture same as Polarity Check but triggers when signal reaches full scale Timed Clip Capture rearms after the desired retrigger time The Trigger Level slider sets the trigger threshold level in percent of full scale O represents dBFS When the slider is to the right of O the scope will trigger on the positive portion of a full scale signal when it is to the left it will trigger on the negative portion of a full scale signal The Retrig Time slider controls the amount of time that the system waits before retriggering when a Timed mode is selected 42 Instruments The Slope Switch controls how the scope is triggered When in the up position the scope will trigger when the signal reaches the threshold level and is moving in a positive direction When the switch is down the trigger occurs when the threshold is reached and is moving in a negative direction The Arm Trigger button manually rearms the trigger Clicking on the Grid disclosure triangle at the bottom of the Control window causes the oscilloscope details window to expand and reveal controls for manipulating the oscilloscope calibration grid or graticule The Grid Vert Spacing slider controls the vertical spacing of the horizontal grid lines The Grid Horiz Spacing slider controls the horizontal spacing of the vertical grid lines The VOffset slid
100. gnal will tend to decrease the coherence of the measurement The fact that there is noise in the test environment is not normally a problem when doing the test we arrange for the test signal to be louder than the surrounding noise Even ifthe signal is not louder than the environmental noise at all times the MBM thresholding allows the Transfer Function to only make measurements when the source signal is louder than the environmental noise There is one situation that is problematic when making acoustic measurements When the system has acoustic reflections the response signal may have hard or partial nulls at certain frequencies These nulls depend on the specific geometry of the acoustic environment especially the location of the test microphone and don t really represent the response of the system A null is created at a specific frequency when multiple signal paths cause the test signal to cancel out at the test mic position ava Reflective Acoustic Surface e g wall table ceiling etc Figure 4 26 Acoustic test with reflected paths The reflected path introduces a copy of the signal with a time delay The reflected signal takes longer to reach the microphone than the direct signal because of the path length difference go ailemion Point A Y E ooo o o n c oo o NA Path e Direct Path Length Length gt Difference Figure 4 27 Path length difference If we call the path length A and
101. h relatively inexpensive high quality flat from 9Hz to 30kHz measurement mics When we start the transfer function using the setup shown in the figure above we get a measurement that looks like this AA Transfir Funtika 1 m Ea L th a ak lik J A EM ate JE Pose agin ratas Lie Glee ire Figure 4 19 Transfer function without delay compensation Since this measurement was made with the microphone close to the speaker the acoustic delay is short As a result the power measurement is reasonably accurate and the coherence is near 1 for most of the audio bandwidth The phase however looks kind of like a sawtooth This indicates that there is a time delay between the source and the response If the time delay was larger the phase would be a sort of random line with values near zero and the coherence would be 0 or close to zero for the entire audio bandwidth Basically we need to time align the signals SpectraFoo provides internal delay compensation to allow you to time align the source and response signals To accomplish this you use the Delay Finder The Delay Finder is accessed from the Transfer Function Control window To time align the source and response signals 1 If the Transfer Function Control window is not visible open it by clicking on the Show Controls button in the Transfer Function window The Transfer Function Control window will appear oO Transfe r Function Cont rals i S
102. h the data created by the Second Trace Mode Thus if the Second Trace Mode is Channel 2 the second trace set is composed of the three traces associated with the second input channel 4 Select the traces you want to save using the checkboxes If you select a checkbox for a trace which is not currently active in the Spectragraph the trace will be saved anyway For example if you take a snapshot of an instantaneous trace but decide that you really want a snapshot of the average also just select the Average Trace checkbox in the Spectral Snapshots dialog The average trace will be saved as a snapshot using the averaging parameters that are currently set in the Spectragraph controls window If you want to take a snapshot of only one channel make sure that the snapshot checkboxes for the channel you want to discard are left unchecked 5 Type any comments you might have about the snapshot into the comments field 6 Click OK The snapshots will be created and the Spectral Snapshots List window will appear 34 Instruments 2 0 8 Spectral Snapshot List Snapshot Name Show In Lal E Song 1 Larg O Song 1 R arg O Song 2 L inst m Song 2 L pk al Song 2 R inst O Song 2 A_pk Figure 3 27 The Spectral Snapshots window The Spectral Snapshots List allows you to assign and display snapshots in Spectragraph instruments You also use the Spectral Snapshots List to access the post processing functions that can be performed on Spectral Snaps
103. hannels are displayed on the scope 3 Subtract Second Channel One trace corresponding to Channel Channel 2 is displayed on the scope 4 Add Second Trace One trace corresponding to Channel Channel 2 is displayed on the scope 5 Multiply Second Channel One trace corresponding to Channel Channel 2 is displayed on the scope Selectable trigger channel The trigger channel is now user selectable This allows you to run the trigger off of Channel 1 Channel 2 or Fither input channel You select the trigger channel with the Trig Chan pop up menu in the Oscilloscope Controls window Power History This instrument allows you to see the history of the information displayed by the Peak and RMS meters The light grey tick marks indicate the passage of one second of time and the height of the color for each time slice indicates the Peak yellow amp RMS purple power levels of the program The ratio between these two levels is responsible for the perceived volume of program material When there is a large difference between the Peak and RMS levels of program material the perceived volume will be low as compared to the peak levels on the tape Conversely when the difference between Peak and RMS levels is small the perceived volume will be louder This instrument can help you determine how much compression and limiting is needed for specific program material If you have a full featured mastering compressor this displa
104. hat you can correct the system using an all cut EQ curve 9 Adjust the settings on your system EQ to match the general trends of the inverted system response curve Avoid trying to match steep peaks in the inverted system response especially when the coherence is very low Assuming everything went well your system has been corrected and should now sound significantly better than when you started You can re measure the system response now with the system EQ switched in to verify that the system has been substantially improved and of course your ears will also let you know There are many other types of measurements you can make with the transfer function measurement system Transfer Function Snapshot Overlays Reference Use the Take Snapshot button in the Transfer Function window to make a new snapshot from the current transfer function data All other snapshot overlay management is done from the Overlay List window 73 The Transfer Function ODO Overlay List Snapshot Name Y S I Fade b Ol system IFT crossover n Mone 5 E System 1FT Top O O O Mone Ol system 1FT hand overh C Mone al System at listening posi Mone a Left Cab Close Mic QO C l Hone Ol Dead End L Close E f4 amp Hone E Lett Average F wi iw Hone E Right Average C Ww Ww Hone O Toral System Average F w El Coherence Figure 4 33 Transfer Function Snapshot Overlays window This window
105. he Tile Windows command is not implemented in this version of the software The Hide All Floating Controls provides an easy way to remove screen clutter by hiding all of the floating control windows at once If no floating controls are visible this command becomes Show All Floating Controls which makes all of the hidden floating control windows visible The next group of commands Hide Routing Window Show FFT Window Control all toggle the visibility of the indicated control window The last group of items in the menu correspond to the list of windows in the instrument window layer Selecting one of these items will bring the corresponding window to the top of the instrument window layer 110 12 Epilogue Welcome to the end of the tour By this point you should have a good understanding of the basic features and capabilities of SpectraFoo It should be clear by now that SpectraFoo was designed with a strong musi cal bias It has profound implications for creative work in such diverse areas as Mastering Recording and Mixing Audio Video Post production Music Synthesis Research Sound Design Musical Instrument Design Loudspeaker Testing and Ethnomusicology among others Although SpectraFoo was designed for the professional engineer it is also an excellent educational tool By giving students quantitative feedback that is synchronized with what they hear SpectraFoo helps to accelerate the development of critical listening skills Usin
106. he sweep This frequency can be any positive value fractional or integer If the frequency entered is negative it will be treated as positive 90 Signal Generator 3 Start Level edit text box The level entered into this box is used as the starting level of the sweep This level is in units of dBFS and may be positive or negative 4 Start Phase edit text box The phase entered into this box is used as the start phase of the signal The phase is in units of degrees and may be positive or negative 5 End Frequency edit text box The frequency entered in this box is the frequency of the end of the sweep This frequency can be any positive value fractional or integer If the frequency entered is negative it will be treated as positive An entry of means use the start value 6 End Level edit text box The level entered into this box is used as the ending level of the sweep This level is in units of dBFS and may be positive or negative An entry of means use the start value 7 Pre Delay edit text box The Pre Delay time is the period of time that will elapse before the sweep starts 8 Duration edit text box The Duration is the period of time that will elapse between the start and end of the sweep 9 Post Delay edit text box The Post Delay time is the period of time that will elapse after the end of the sweep before the sweep loops around Each sweep in the generator loops after the pre delay duration and
107. he total harmonic distortion plus noise measurement Both measurement are shown as a percentage as well as their levels in relative dBr and full scale dBFS units The THD Meter also shows the input level referenced to full scale By clicking the A Weight checkbox the results may be weighted To properly use the THD meter use must analyze a single frequency signal An easy way to do this is by using SpectraFoo s Signal Generator with synchronization enabled 54 4 The Transfer Function Overview For live sound equipment testing or any application where you need to analyze the characteristics of acous tical and electrical audio systems SpectraFoo provides Music Based Measurement MBM SpectraFoo us es a transfer function display to show you the relative power and phase response between the left and right channels The transfer function display assumes that the signal connected to the computer s right input is a source signal and the signal connected to the left input is a response signal Audio or Acoustic System Response SpectraFoo Figure 4 1 SpectraFoo Signal Arrangement for MBM Transfer Function When the source signal is the input to some audio processing arrangement and the response signal is the mea sured output of the system you can use music as your test tone SpectraFoo uses the source signal as a point of reference and the transfer function display shows the differences in amplitude and phase
108. herence Figure 4 31 Transfer function Overlay List window You now have a complete measurement of the transfer function of your system You may want to make a number of measurements for further averaging but what we have now is good enough to illustrate the cor rection process Here is an example of a measurement that we have made using the procedure described above Ae Tranalor Finiti T Pr et Frequency aK 1 50 an m i X x4 E of 41m 150 41m 1 Fa wa E th a ak Vie EM ate JE Bate agin remain Lie Gia are Figure 4 32 Sample transfer function We see that the coherence is reasonably high with a few narrow exceptions from about 80 Hz to 18 kHz Below 80 Hz the sound system is not really reproducing the test signal and the environmental noise is pretty high In addition the test signal does not have a tremendous amount of energy below 60Hz The test signal did not have much energy above 18 kHz so we have not really measured the system response from that point on There are a few significant dips in the system response Some of these are quite narrow and correspond to significant dips in the coherence curve These dips are most likely caused by measurement nulls due to acoustic reflections and must be ignored since the coherence is so low Some of the dips in the response correspond to places where the coherence is high These dips are real and can be corrected with EQ Notice
109. his means that on average the signals do not line up with each other The coherence will be close to zero If the SUT is stationary e g it is linear does not change over time and passes at least a portion of the source signal the coherence will be 1 for all frequencies This is what we expect when we make a time aligned measurement on an electronic system like an EQ If the SUT is non stationary or if the SUT does not pass any of the source signal in a particular frequency band then the coherence in that band will be 0 Unless we are having big problems the frequency bands for which the coherence is small or O should be limited even with acoustic tests If the coherence is O or near O for most of the audio bandwidth this indicates that the SUT is either not properly connected the measurement has not been time delay compensated with the delay finder or that the SUT is sufficiently nonlinear that it is not possible to analyze it with the transfer function a distortion generator is an example of such a device 68 The Transfer Function Under normal acoustic test conditions the response signal of the system will be the actual system response plus noise The noise which can be electronic or acoustic is by definition uncorrelated with the source signal The coherence of noise with any source signal except an exact time aligned copy of the noise is zero As a result the noise that corrupts the response si
110. hot of the current Transfer Function data and adds it to the Transfer Function Snapshots window You can use Transfer Function snapshots for a number of measurement and comparison tasks These are described in greater detail later Overlay List Figure 4 12 Overlay List Clicking on the Overlay List button shows the Transfer Function Snapshots window 61 The Transfer Function Clear Data Figure 4 13 Clear Data Clicking on Clear Data clears the current transfer function data and resets the transfer function to flat This is useful when you start measuring a new system or device or move a test microphone and you want to start the measurement from scratch The Transfer Function data is displayed in two different panels 16 31 63 125 250 500 ik 2k 4k 8k 16k Figure 4 14 Power Panel The power panel displays the relative power between the response signal and the source signal as a function of frequency The relative power curve is drawn in green The vertical calibration is in units of dBr decibels relative The horizontal calibration is in units of frequency Hz The limits of both the vertical and horizontal scales are controlled with the Transfer Function control window The power panel also displays the coherence of the measurement as a function of frequency The coherence curve is displayed in red The vertical scale of the coherence is linearly scaled The vertical limits of the coherence which are not displaye
111. hots To assign and display a Spectral Snapshot in a Spectragraph 1 If the Spectral Snapshots List is not visible choose Show Spectral Snapshots Window from the Window menu 2 Use the Show In pop up menus to the right of the snapshot names to assign snapshots to particular Spectragraphs AAOH Spectral Snapshot List Snapshot Hame Show In p O int Mic Drums 1 Larg none pa El int Mic Drums 1 A avg 1eLB Left LB Right E LB Drums 1 Left arg 2eLeft Right E LE Drums 1 Right arg A Figure 3 28 Show In pop up The snapshot will appear in the Spectragraph you choose You can display each snapshot in any number of Spectragraphs Simply select each Spectragraph that you want the snapshot to appear within a Mm Figure 3 29 Snapshot assigned to a Spectragraph 35 Instruments Each Spectragraph that you create in SpectraFoo displays a number and the name of the channels routed to it on the left side of the instrument window The numbers are assigned to Spectragraphs in the order they are created So the first Soectragraph you create will be numbered 1 the second Spectragraph 2 and so on The Spectragraphs that appear in the Real Time Rack window are a special case These instruments are numbered 254 and 255 These numbers and channel names match the items you will find in the Show In pop up in the Spectral Snapshots window This allows you to assign a snapshot to any Spectragraph you want without confusion To cr
112. i Bass DI Drums OH nc a Figure 2 5 Active Channel pop up menu with custom channel names The control window for each instrument also contains the parameter library pop up menu in the upper left hand corner This pop up provides access to an integrated library system You can use it to save and recall snapshots of the instrument s configuration All the snapshots you create are available to instruments of the same type and are maintained between each use of SpectraFoo The control window for each instrument also contains the Groups pop up meu in the upper right hand corner The Groups pop up menu provides access to a flexible parameter linking system The items listed in the menu are the names of parameter groups By selecting one or more groups you add the instrument to one or more parameter group Each parameter group will automatically broadcast all parameter changes from any member of the group to all the members of the group By configuring your parameter groups and adding various instruments to the groups you can keep the state of multiple instruments synchronized as you change the configurations of the instruments One of the really cool features of parameter groups is that they allow you to link between instruments of different types For example you can link the frequency controls between Spectragrams and Spectragraphs 15 SpectraFoo Basics For the real time rack window you have an additional way of controllin
113. iauc 29 SS PINK INGISE WIth WW Ite 15 PAD ances a ora seuaten a A T E eae eee 29 Dla WV Ie Nore AW IU PHANG IS F lae sa 29 315 White NOISe With Wie IS Flat a O dae ea 29 2 LGsINCCeSsING race Color CONTOS ada A A A ide estimated aruicercdes 30 Sula Te MacOS COJO PIEKE send aa 30 3 18 Spectragraph display Resolution POP UP occoocccncccnccnnnccnnncnnncnnnccnnncnnncnnnncnnnconnncnnncnnnnnnnncnnnrnnoninnns 31 SO octavedisplay NOSOMILION si s n 31 320 WA octave display SOUL OM E A SS 31 Dle US OClAVE display TEST 2 as 32 32 MINO cta Ve CISD ay FESO ON cs 32 329 END OCA VEO SPA ESO ON SS AA ES 32 324 T24 octave display ESOO A A idle snes As 33 o peca crap Snap BUON a NS sea aesa eae eee es 34 326 The Spectral Spapsh ts dialog ii 34 327s The Spectral Snapshot WINCOW 0 A E E arel eehowesneneeeacg 35 A E A A A A aeeeceect 35 3 29 SWADSMOL assienecaiiana SPECIA PIT iS 35 3 30 Selection for Snapshot Averaging ri dit 36 33 La The Spectral Snapshots MiNkMEenU SS a ES 36 o A Dalo a E EE EA 36 3 33 Average appears in the Spectral Snapshots List A 37 3 34 The Transfer Function Snapshot Dialog ssssssssssesssessresseserssreserssrssreserserssreserssresreserseessreseesses 37 3 35 Transfer Function Created From Two Spectral Snapshots occcoccconccnnccnoccnnncnnnncnnncnnnccnnncnnnccnnncnnns 38 3 36 Spectragram horizontal orientation cccseccesccnseccsccnsscesscceccntsceecentsceesscnseceassenssenaeseee eens 39 953 7
114. ibrary pop up that appears in the instrument itself when you click and hold the controls but ton To access this pop up click the controls button and hold for about a half of a second Alternatively you can command click the controls button to pop up the menu immediately 13 i 0 H L F 0 H R Save Parameters Save Parameters AS Factory Default Figure 7 2 Accessing the presets library pop up from the controls button Modifications of parameter libraries can be cloned to create new libraries using the Save Parameters As command Window Sets SpectraFoo has a Window Set system which allows you to create and store your own personal instrument configurations You can create a complete snapshot meter positions visibility configuration channel routing etc of the entire state of the system and save it as a preset document You can also assign a snapshot to a hot key for instant one key access to various metering configurations To create a window set 1 First create an instrument configuration that you like For example you could make two Spectragraphs assigned to left and right channels a Level Meter a Lissajous scope and a Phase Torch 2 Arrange the instruments the way that you want them to appear on the screen and set each instrument s parameters to taste 3 Choose Save Window Set As from the Sets menu a dialog will appear 86 Workflow Features Please name the window set Recall Mi Visi
115. ime field in the Capture Overview Window can display its value in several different themes Hold the command key down and click on any of the time readout fields to access the pop up menu End Full Time Code een Pictures a Hours Minutes Seconds with fractions Start 00 00 00 000000 Length 00 02 44 339 caconds End 00 02 44 339229 Cursor 000000002044 gt Time Code 29 32 35 38 41 44 47 50 53 56 59 1 prprrparprrprrprrprrprrprrjrrirriti Hours Minutes Seconds Hours Minutes Seconds milliseconds Figure 10 27 Numeric Time Selector Bar 103 Capture and Storage Measuring time between two events Using the loop start and end points SpectraFoo can measure the time between two audio events in a capture 1 Put the cursor at the first event in the timeline and click the loop start time button 2 Put the cursor at the second event in the timeline and click the loop end time button The A field will show the time between the two loop points you can option click the value to select the desired time scale You may also use the mouse to fine tune the position of the loop points in the ribbon For example you could use the Transfer Function s Delay Finder to take an impulse of a full range speaker and subwoofer then turn the impulse into a capture By measuring the time difference between the leading edge of the speaker and subwoofer impulses you can determine the correct value to delay the speakers to each o
116. in the Capture Overview Window the A field shows the change in time between the loop start and end points See Ohm To increase gain To decrease gain Decibel a logarithmic unit of measurement used to describe sound levels relative to a reference level both acoustically and electrically There are several suffixes added to dB to indicate the reference quantity or weighting function used e dBFS Decibels relative to full scale O dBFS is the maximum level in a digital audio system since the level cannot go over 0 e dBu Decibels relative to 0 775 volts across a 600 Q load e dBV Decibels relative to 1 volt with no impedance specification Device Under Test Term referring to an audio device to be tested for example an EQ Fast Fourier Transform The mathematical algorithm SpectraFoo uses to analyze audio The measure of a device s ability to increase the level of an audio signal Unit of frequency defined as the number of times per second the amplitude of an audio signal cycles from O to full positive to full negative back to 0 115 Impedance K System L Linear Glossary Figure 183 One cycle The abbreviation Hz is used to indicate frequency 60 Hz means the signal makes 60 cycles per second For large values a k is used to indicate that the value is multiplied by 1000 For example 15 kHz is 15 000 cycles per second The opposition of a circuit to alternating current In audio it is import
117. ion and padded clips They can also be used for bit clone testing and for looking at low level structures like dither 1234945678 8 10 1172 13 1415 16 17 18 18 20 21 22 23 24 F F F F F F F F F F F F F F F F Figure 3 63 16 bit signal in the Code Meter The Code Meter displays the range of sample codes exercised in the assigned channel in each time slice It shows the activity in each bit of the sample word and shows you which bits are being exercised This can be used to tell for example how wide the samples in the signal are The example above is a 16 bit signal so only the 16 most significant bits MSb are being exercised Code Matrix Meter The Code Matrix Meter is designed to work with 16 bit delivery media and only utilizes the top 16 bits of the samples in the signal The meter takes the 16 bit samples and divides them into two groups the most significant byte MSB which is the top 8 bits and the least significant byte LSB which is the bottom 8 bits Most Significant Byte MSB Ignored Least Significant Byte LSB AA signed unsigned y aaa Figure 3 64 Definition of the offsets in the Bit Matrix Origin of Matrix x y Figure 3 65 Visual of the Bit Matrix 51 Instruments For each sample these groups are then converted to horizontal MSB and vertical LSB offsets into a 256x256 pixel matrix For each sample in the time slice the corresponding pixel is turned on Figure 3 67
118. ir Mode pop up menu Routing the Signal Generator Output SFC The output of SpectraFoo Complete s Signal Generator appears on the Internal channels in the Analyzer Routing Window While there are multiple Internal Channels they all carry the same mono output from the Signal Generator These channels can be routed to Analyzer or Output channels or both e By routing the Signal Generator to an Analyzer channel you may view its output in any of SpectraFoo s instruments For example if you assign Internal 1 to Analyzer 1 the output of the Signal Generator will appear on any instrument that looks at Analyzer 1 e By routing the Signal Generator to an Output channel you will send it to the audio outputs of your computer or audio interface The output of the Signal Generator will be routed according to which output channel the Internal chan nels are routed to For example if Internal channels are routed to Output 1 and 2 the Signal Generator signal will be appear on outputs 1 and 2 of your audio interface If you wanted to route the Signal Generator to outputs 3 and 4 you would route Internal channels to Output channels 3 and 4 On Metric Halo interfaces SpectraFoo s Output channels correspond to DAW Channels Output 1 and 2 are DAW 1 2 Output 3 and 4 are DAW 3 4 etc 83 6 Physical Unit Calibration To change the physical unit calibration amp clipping parameters in SpectraFoo 1 Choose Level Calibration from the Analyzer m
119. its that the lll Rate Avg Mode Log 4 Spectragraph appliesto its display Settling Time 7357s Gives a precise numerical reading ofthe This lets you zoom in on a particular Frequency Scalin Power Scaling settling time of the average trace frequency range As you change the low and high frequency limits Frequency Range 0 Hz 16 10 kHz the frequency calibration on the ESOO oops The Frequency Scaling and Power bottom of the Spectragraph will 81631 62 125 ae Fides 2k dk Sk 16k Scaling sliders allow you to adjust the instantly rescale itself scaling of the frequency and power calibrations When the slider is set to its far left limit the scale is roughly linear TUONO 0 TOL 0 TCL AAn 38 82 76 70 64 58 52 46 40 34 28 22 16 10 4 Use these sliders to change the low and high power limits that the Spectragraph applies to its display When the slider is set to its right limit This lets you zoom in on a particular power range As you change the low and high frequency limits the scale is logarithmic The best way to the power calibration on the left side of the spectragraph will instantly rescale itself get a feel for scaling is to simply grab a slider and move it back and forth The frequency and power calibrations will track your movements in realtime and useful scaling settings will quickly become obvious Figure 3 8 The Spectragraph and controls The Spectragraph utilizes a triple display for each input ch
120. k on the tile and choose the new color 3 Select Coherence from the Fade pop up menu of the snapshot in the Overlays window This will fade the trace based on the coherence of the measurement It allows you to see what portions of the response are equalizable 4 Start your signal source Pink noise tends to work best when you are measuring your EQ because you don t have to listen to it You can still use music if you want to be able to listen to the effects of the system EQ as you are changing the system EQ 5 Since there is very little environmental noise in this measurement you can decrease the setting of the Avg Power Cutoff slider 6 Again since there is very little environmental noise and since we want to be able to see the changes in the equalizer response as we change the equalizer settings you can decrease the setting of the Avg Rate slider 7 Click the Compute Delay button to recompute the delay for the equalizer The system will compute and compensate for the delay through the equalizer After a few seconds the coherence curve should be near the top of the panel for the entire audio range and the power curve should be flat this assumes that the EQ has been zeroed out 8 Move the inverted system response curve so that the highest points on the curve are level with the live trace You do this by clicking on the response curve and dragging it vertically until it is positioned properly You want to make this adjustment so t
121. l Draw Peak Level as Bar M Use PPM ballistics M Draw Holds as Arrows Draw YU as Solid Bar wi Auto Release Holds Use AES Std RMS Ref Use Solid Color Transitions 0 Safe Until 30 00 dEFS El aay TH TTT MT TTT TT TTT TTT NTT UMA TT TT TTT 23 22 76 70 4 58 52 46 40 34 25 2 16 10 4 Caution Level 15 00 dEFS O pa TTT Me TTT TO OC HIJO an 20482 76 70 64 58 52 46 40 34 8 22 16 10 4 Danger Level 1 00 dBFS I O A PTETETPE EEO TTT ETET ETT EE H S82 r6 10 64 38 52 46 40 34 25 22 16 10 4 E Peak pes C vu Figure 3 7 Level Meter Options Window 2 Check Use PPM Ballistics The meter will now use the standard PPM decay time You can change the decay time using the PPM Settling Time slider Meter scales SpectraFoo now has a variety of User Selectable scale calibrations In addition to the equally spaced level calibration aptly called the SpectraFoo Calibration you can choose from the following international PPM and VU standards UK PPM UK Standard 1 7 Scale Line up calibration is O dBu for marking 4 EBU PPM EBU Standard PPM Scale Line up calibration is O dBu at marking Test IEEE PPM IEEE Standard PPM Scale Line up calibration is O dBu at marking Test IEEE VU IEEE Standard VU Scale Line up calibration is 4 dBu at marking 0 DIN PPM DIN Standard PPM Scale Line up calibration is 6 dBu at marking 0 Nordic PPM Nordic Standard PPM
122. l generator parameter sets are available these parameter sets illustrate some of the wide variety of sounds that can be created with the generator They can be downloaded from http www metric halo com media SignalGenParams zip 95 9 Controlling the FFT Window These handles allow you to smoothly change the shape of the FFT window in realtime Click on a handle and drag it around to change the shape of the window The realtime instruments will reflect the change instantly This feature was provided for users who are experienced with the mechanics of FFT analysis as an effective way to compare different windowing schemes If you are not intimately familiar with the concept of FFT window ing you will probably want to keep using the presets For music analysis the Hanning window is usually the best choice O FFT Window This is a graphic display of the mathematical window being applied to the FFT 7 Add current window to the presets Add to Library Delete from Library Delete a preset Rectangular Window Triangular Window Hanning Window Hamming Window Blackman Window These are the FFT window presets that come standard with SpectraFoo When you choose a new preset the graphic display will change to match your Snap a ghost of the current selection window Figure 9 1 FFT Window Control Window The FFT assumes that the block of samples it is ope
123. lat the Spectragraph shows the sum of the power of all of the spectral lines in the FFT that fit into each point in the displayed trace This has the effect of displaying pink noise or noise that has an equal amount of power in each octave as a flat line This mode is traditionally used when the frequency scale of the graph is logarithmic and corresponds to the type of display available on a traditional RTA The figures below show the results of the two weighting accumulation modes with the two different kinds of noise 28 Instruments Figure 3 12 Pink Noise with Pink is Flat F WAU eR ei Sapee esa ssssaeesss eee Figure 3 13 Pink Noise with White is Flat de dn dy F WROD a ON do tu 1y Ly dn dn dn dn dn dndn h h h do d do do o b b a a la D A N D o o O SALINIDAD N A a o O a EE Ba ub dab do do bra drid Figure 3 14 White Noise with Pink is Flat RERRRLLL DONA IB o 1 L 7 3 4 D i g I t a I 1 3 4 D 4 n a P Bb do do do ta ta tu dn dn dn dn dn dn dn b b b do go Ja Figure 3 15 White Noise with White is Flat Physical unit calibration SpectraFoo can be globally calibrated to Physical Units i e dBu dBV You can use dBu units in the power calibration for the Spectragraph by checking the Use dBu Calib checkbox in the instrument s Spectragraph Control window See Physical Unit Calibration In SpectraFoo for more information about physical unit cal i
124. listics e Spectragram history display to accompany Spectragraph Like a topological map of your signal beau tiful amp informative e Timecode clock running display of current timecode source e Oscilloscope configurable triggerable dual channel audio frequency oscilloscope Provides high res olution wave form display and simple waveform math Versatile triggering modes make this ideal for a variety of measurements e Power History shows a running history of the peak and RMS level of the metered signal e Envelope History shows running envelope of the metered signal similar to a DAW overview e Band Power History shows the running history of the total power within a specified bandwidth around a specified center frequency e Phase Torch Metric Halo s unique two channel phase visualization tool displaying phase as a func tion of frequency independent of power e Lissajous Phase Meter familiar X Y mode O scope two channel phase meter with a twist supports X Y mode Lissajous mode and Stereo position mode Also supports auto gain control to provide useful readings during fades or other very low level material e Power Balance unique meter that shows the history of the relative power between two channels Perfect for balancing mics or for monitoring the relative stereo soundfield balance e Correlation A favorite in European broadcast circles shows an instantaneous representation of how mono compatible the monito
125. lists all of the overlays that are loaded into the system Each item in the list contains the following items 1 A color well This is the base color of the response traces in the snapshot Clicking on the chip will bring up the color picker window and allow you to change the trace color 2 The snapshot name This is the name associated with the snapshot data You can click on this to select the snapshot in the list Double click to bring up the transfer function snapshot edit dialog You can change the name of the snapshot its associated comments and the offset The offset can also be con trolled by clicking and dragging the trace in the Transfer Function window You can use the offset field to easily reset the trace position snapshot taken Sun Aug 21 2005 9 33 10 PM snapshot Mame System 1FT crossover null Comments Invert Trace ES Offset dE E Smooth Trace ds o Cancel oa Figure 4 34 Transfer function snapshot edit dialog 3 The V checkbox controls the visibility of the associated snapshot in the transfer function window lt option gt clicking this check box will set the state of all of the snapshots in the list 4 The S checkbox controls the smoothing of the response traces of the associated snapshot in the transfer function window lt option gt clicking this check box will set the state of all of the snapshots in the list 5 The I checkbox allows you to select if the response tra
126. ll as many different versions of the same instrument monitoring the same channel You can also monitor multiple channels simultaneously With the analyzer pop up in the control and routing window you can set the number of channels you want to be able to monitor simultaneously If you set the number of Analyzer Channels to 2 you will be able to actively monitor two channels from your input hardware at one time However the number of analyzer channels within SpectraFoo and the number of hardware channels are independent The number of hardware channels 78 Controlling Audio and Instruments depends on the hardware input path that you are using Once you have selected an input path you can route from any of the hardware the analyzer channels the fly without stopping the audio using the analyzer channels pop ups in the Control and Routing window this is described below The number of channels you can analyze simultaneously is limited by the speed of your Macintosh If you are using a fast computer you will be able to monitor 24 channels simultaneously with impressive update performance If you are using a slower machine the update rate might appear sluggish The default number of analyzer channels for SpectraFoo is two This will work fine on any Macintosh capable of running SpectraFoo SpectraFoo is fully qualified to run at all channel depths on all Intel based Macs If you do not have one of these machines it does not mean that you cannot run Spec
127. me delay lag of the maximum value of the impulse response is in general the delay time of the SUT If the SUT is acoustic we expect to see a number of smaller copies of the impulse response at different lags These copies correspond to acoustic reflections from walls desks etc If the SUT is time aligned the impulse response will be relatively compact The impulse shown in the Delay Finder Window figure above is of a small professional PA speaker The small dip in the impulse response that occurs before the main impulse corresponds to the start of the impulse response of the low frequency driver The larger spike is the start of the impulse response of the high frequency driver The speaker is not fully time aligned As a result we will not be able to fully time align the measurement Working with extremely long delays SpectraFoo s internal compensation can delay the source signal by up to 1 5 seconds This corresponds to an acoustic delay of almost 6 football fields at standard temperature and pressure and should be sufficient for most work If you need to compensate a larger delay you will have to use an external delay line The Delay Finder automatically finds the lag at the maximum value of the impulse response and uses that time delay to set the internal time delay compensation on the source channel You can tweak the delay by moving the cursor in the Delay Finder window After we have compensated for the response delay the tra
128. me jurisdictions do not allow the exclusion or limitation of incidental or consequential damages so this exclusion and limitation may not apply to the Licensee It is mutually acknowledged that the Licensee must read the manual to coordinate the equipment requirements needed for the system including but not limited to the capacity of all speakers intended to be used by Licensee in conjunction with the subject Software Licensor shall not be liable in any way whether for direct damage or consequential damage or any other portion of the system that is damaged as a result of Licensee using the subject Software 6 PROPERTY RIGHTS OF THE LICENSOR This Software is the exclusive property of the Licensor whether personal property and or intellectual property or otherwise The Software is subject to both the Patent Laws and the Copyright Laws of the United States of America There is a pending patent application at the United States Patent Office All of the material whether in terms of printed media or software is copyrighted to the fullest extent permitted by law All rights are reserved by Metric Halo Laboratories Inc 7 U S GOVERNMENT USERS If you are a U S Government user then the Software is provided with RESTRICTED RIGHTS as set forth in sub paragraphs c 1 and 2 of the Commercial Computer Software Restricted Rights clause at FAR 52 227 19 or subparagraph c 1 11 of the Rights in Technical Data and Computer Software clause at DFARS
129. mes that you have a basic working knowledge of the Mac OS and its standard techniques If you are new to Mac OS X you should consult your Apple documentation before continuing System Requirements e A Macintosh computer running Mac OS X 10 4 11 or newer We generally recommend that you use the latest available version of the OS If you are using one of the previous releases 10 4 or 10 5 we recommend that you updated to Apple s final System Update for that release Metric Halo only tests SpectraFoo with the final System Update of previous OS releases e RAM while SpectraFoo is completely compatible with OS X virtual memory like all media applica tions it benefits from more available physical memory As a practical rule of thumb all OS X systems ought to have at least 2 GB of physical memory installed 4 GB or more preferred If you plan on using the capture engine or the delay finder you will benefit from having more physical RAM installed but it is not required for correct operation e OpenGL SpectraFoo can optionally take advantage of OpenGL acceleration to increase performance reduce system loading and reduce the likelihood of the fan turning on when used on a laptop In order for SpectraFoo to use OpenGL your system must be capable of supporting Apple s Quartz Extreme technology All shipping Macs support this technology and this has been the case for a number of years 12 Introduction at the time of this writing
130. meters are linked by the group Instruments can be added and removed from any or all of the groups at will To name and control which parameters are linked by a group 1 Select Show Link Groups Window from the Sets menu The Link Groups Window will appear A O Link Groups a Ena Link Group Hame O RAAR m al e M Figure 7 6 Link Groups Window 2 Double click the group you want to edit The Link Groups Edit Window will appear 88 Workflow Features a 6 8 Edit Link Group SR SEL omr nane Ena Parameter Hame Ei Channel 1 P as Channel 2 ce Enable D Solo Octare Mode Max Power Mn Power Max Freg 144444414 Figure 7 7 Link Group Edit Window 3 Type the new name for the group 4 The scrolling list in the window lists all of the available parameters in the system only parameters for instruments that have been instantiated will appear Each parameter has an associated checkbox that indicates whether that parameter will be distributed to other instruments in the group To disable a pa rameter unselect its associated checkbox To disable all of the parameters select Disable All Parameters from the window s mini menu Conversely to enable all of the parameters select Enable All Parameters from the window s mini menu 5 Close the Link Group Edit Window when you are done making changes To disable a group 1 If the Link Groups Window is not visible Select Show Link Groups Window from the
131. most recent recording are retained and can be used to record material that occurs at the same time with respect to the external timecode source You can use this to grab multiple aligned tracks of audio or to record the same audio with different types of processing All recording is controlled and initiated with the Capture Control Window found in the Window menu There are three basic capture modes that you may use each with a different user interface All three modes have several controls in common e You may switch capture modes via the Mode pop up menu e The Avail Time field shows how much audio may be stored in RAM e If the 24 bit box is checked the capture will be recorded at 24 bits Otherwise it will be 16 bit e The Stop and Record buttons control the capture mechanism The capture modes are 1 Manual Use manual mode to record on the fly Click the record button to start recording and click it again to stop recording Capture Control Mode Manual Avail Time 01 40 05 748390 Figure 10 1 Manual Capture Mode 2 Level based auto punch Use level based auto punch to start and stop recording based on the volume of the audio being monitored This is great for capturing individual drum beats or for capturing entire songs A specific example of the usefulness of level based captures is when you are trying to determine the optimal placement of microphones on a drum kit When coupled with the Auto Arm feature lev el b
132. n Time runs from right to left with higher levels indicated by brighter colors The Spectragram may also be configured to display time running from bottom to top by Option clicking the instrument or in the Spectragram preferences Figure 3 37 Spectragram vertical orientation Using the Spectragram in vertical orientation along with the Spectragraph can give you two very different yet complimentary views of your audio 39 Instruments EmA san AS RATRE ESO ARE Eo E RE Figure 3 38 Using the Spectragram and Spectragraph together It is very easy to get the frequency ranges and scales synchronized using Link Groups The Spectragram preferences are very similar to those for the Spectragraph h i Spectragram Controls Factory Default ay Groups Frequency E 113 F dl Scroll Vertically diet Scaling Power Scaling Frequency Range 10 Hz 22 05 kHz Active Channel i L re Pry ery eurpPurypPreryrerypreryprey amp 16 31 62 125250500 1k 2k 4k 8k 16k Power Range 8882 76 70 64 58 52 46 40 34 28 22 16 10 4 A A A US SE _ a Figure 3 39 Spectragram preferences e The Preset menu allows you to save and recall setting presets e The Groups menu allows you to assign Link Groups e The Active Channel menu selects the analyzer channel that the Spectragram will display e When Scroll Vertically is enabled the display wil scroll from bottom to top When disabled the display will scroll from right to left
133. n function and a uniform frequency pdf This means that all sample values are equally likely and all frequencies are equally likely The parameters for the white noise generator are Figure 8 4 White Noise Parameter Cluster 1 Enable checkbox Checking this turns on the additive white noise 2 Start Level edit text box The peak level of the white noise at the start of the sweep This level is in units of dBFS and may be positive or negative 3 End Level edit text box The level entered into this box is used as the ending level of the sweep This level is in units of dBFS and may be positive or negative An entry of means use the start value 4 Pre Delay edit text box The Pre Delay time is the period of time that will elapse before the sweep starts 91 Signal Generator 5 Duration edit text box The Duration is the period of time that will elapse between the start and end of the sweep 6 Post Delay edit text box The Post Delay time is the period of time that will elapse after the end of the sweep before the sweep loops around Additive pink noise with sweepable level The signal generator also provides additive pink noise The pink noise generated by SpectraFoo is 1 f noise with a low frequency roll off This means that above 30Hz the frequency distribution of the noise has equal power per octave The controls for the pink noise generator are Pink 0 RMS i lo 3600 o Figure 8 5 Pink Noise Parameter
134. napshots List 36 Instruments aos Spectral Snapshot List Snapshot Name Show In b E LB Drums 1Left arg O LE Drums 1 Right avg m Internal Mic Average Figure 3 33 Average appears in the Spectral Snapshots List Now the average can be displayed in a Spectragraph as a snapshot To create a Transfer Function from two Spectral Snapshots 1 Select the two snapshots in the Spectral Snapshots List 2 Choose Create Transfer Function from the Spectral Snapshots mini menu 3 The Transfer Function snapshot dialog will appear Snapshot taken Wed Aug 17 2005 11 47 14 AM Snapshot Name Mobile O crossover null Comments Source int Mic Drums 1 R avg Response int Mic Drums 1 Lavg M invert Trace Offset a Se Figure 3 34 The Transfer Function Snapshot Dialog 4 Name the Snapshot and add any comments you might have By default SpectraFoo labels the source and response channels The source channel will be the channel that appears first in the Spectral Snap shots list 5 5 Click OK SpectraFoo will automatically open the Transfer Function window and display the newly created Transfer Function 37 Instruments 606 Transfer Function F Power Ys Frequency Rel Power 16 31 3 125 50 300 1k Zk dk Bk 16k b Phase ws Frequency Mi Soto Jl Take Snapshot Overlay List Clear Data Figure 3 35 Transfer Function Created From Two Spectral Snapshots You can
135. nking filter and exhibits equal power per octave in all frequencies Commonly used to test the frequency response of devices and audio reproduction systems Peak Programme Meter Also called a Peak meter this type of meter shows instantaneous signal ac tivity Root Mean Square Describes the average energy of a signal The measurement of how much a signal has been corrupted by noise System Under Test Term referring to a complete audio reproduction system to be tested for example a PA Total Harmonic Distortion The measurement of all distortion components of a signal Volume Unit 119 W White Noise Glossary A scale of measurement of audio energy that averages high and low levels to show perceived loudness Random noise with equal power within a fixed bandwidth White noise con tains more high frequency energy than pink noise 120 Index A Analyzer Adjusting the number of channels 79 Changing the analysis depth 80 Channels 78 Configuring the routing matrix 80 Control amp Routing window 78 Master Controls window 76 Sum amp Difference monitoring 82 Analyzer menu 108 Analysis points 108 Level Calibration 108 Remove DC Offset 108 Reset Analyzer 108 Signal Generator 108 Audio I O menu 108 Buffer Size 108 CA Driver 108 Configure Hardware 108 Monitor Input 108 Sample Rate 108 Use Internal Clock 109 B Band Power History 49 Buffer Size 108 C CA Driver 108 Ca
136. nsfer function measurement becomes 66 The Transfer Function 85 TranaTor Furti ET al 1 m xa L th a ak 1i Eli E ise agen rap Lie ear ere Figure 4 22 Time aligned transfer function Notice that overall the coherence of the measurement has increased and that the phase no longer has the sawtooth character As explained earlier the phase is not discontinuous at 2 kHz it is just wrapping around due to the cyclic nature of phase The reason we cannot get the phase measurement to appear continuous for this system is related to the fact that the system that we are measuring is not time aligned When the measurement of the low end is time delay compensated the high end is not and vice versa Interpreting the Data So now we have a measurement of the transfer function of the system This leads us to a few natural questions 1 What does the data mean 2 How do we interpret the data 3 How do we use the data The transfer function measurement system calculates three different functions from the source and response signals Each of these functions adds a piece of the puzzle and will be instrumental in interpreting and using the transfer function data The first function is the power response of the SUT This is the effective equalization that the SUT applies to signals that run through it The second function is the phase response of the SUT This is the phase shift distortion applied to the signal by the SUT
137. on the bench do not necessarily guarantee exceptional sound quality It is our belief that this discrepancy is due in large part to the dynamical behavior of electronic systems Until now it has been impossible to test systems with signals that properly stimulate this dynamical behavior The heretofore available test equipment simply was not fast enough to analyze and display measure ments that provide any meaningful information about the dynamical behavior of audio devices in the presence of real musical signals SpectraFoo provides the technology that makes dynamical testing possible We hope that you will get as much enjoyment and insight from working with SpectraFoo as we have gotten from developing it Developer s Note Please feel free to stress SpectraFoo as much as possible Our primary design objectives have been to create a system that is not only extremely fast and easy to use but also stable and robust We believe that software should not surprise you shouldn t break and should never ever crash the computer it is running on If you encounter any stability problems with SpectraFoo please contact us immediately 111 13 License Agreement LICENSE AGREEMENT METRIC HALO DISTRIBUTION INC SOFTWARE LICENSE AGREEMENT AND WARRANTY IMPORTANT PLEASE READ THIS SOFTWARE LICENSE AGREEMENT CAREFULLY BEFORE INSTALLING AND USING THE SOFTWARE By installing the Software the Licensee is consenting to be bound by and becoming a part
138. or surround group of instruments as well as synchronizing the settings of different types of meters on the same channel Figure 7 4 Grouping System 87 Workflow Features Figure 7 5 Parameter Passing The grouping system allows you associate any number of instruments with any of the groups Each instrument may be simultaneously associated with as many groups as needed When an instrument that is attached to a link group e g Spectragraph 1 in the figure above has a parameter changed in its control window it sends the parameter change to all of the groups to which it belongs e g Group 1 for Spectragraph 1 both Groups 1 amp 2 for Spectragraph 2 etc If the parameter is one that has been enabled in the group it is passed to all of the instruments that are linked to the group The figure above shows a parameter sent from Spectragraph 1 to Group 1 Group 1 forwards the parameter change to Spectragraph 2 and Spectragraph 3 Since Spectragraph 4 is not a member of the link group it does not receive the parameter update If Spectragraph 2 originated the parameter change and both Group 1 and Group 2 were enabled for the parameter all of the Spectragraphs illustrated above would receive the parameter update There are 32 link groups available in the system They are all installed and enabled in the software as it ships You can rename the groups to indicate what information they use for linking You can also control what types of para
139. other instance of the particular instrument to the system and creates a new instrument controller item Click on the show hide checkbox of the new instrument controller item and a free standing resizable window will appear containing the selected instrument Each instrument class can have many instances You could for example create four Spectragraphs to monitor the left channel one adjusted to monitor the entire audible spectrum one zoomed in on low frequencies another zoomed in on the midrange and another focused on the high end You could create another 4 instances 76 Controlling Audio and Instruments set the same way but assigned to a different analyzer channel Of course if you want the consolidated view provided by the virtual rack interface simply click the show hide icon for the Real Time Rack in the Master Controls window and SpectraFoo will create a consolidated two channel metering view To remove an instance of an instrument click on its remove button in the Master Controls window A dialog will appear as shown below Are you sure you want to remove this instrument Cancel Figure 5 3 Instrument removal window If you wish to avoid this dialog option click the remove button in the Master Controls window The instrument will be immediately removed Channel assignment is controlled via the instrument s details window nn 5 pectragraph Controls Factory Default F Groups 4 g Second Tra Rig ht po
140. ource Internal 1 E Response intemal 2 E Resolution Continuous H Frequency Range 6 Hz 22 05 kHz pra pra para para pra para parar partit 816 31 62 125 250 500 ik k dk Sk dk Power Range 40 008 40 00d6 0 Mn Ba aa ae a aati a a ds did Scaling Avg Rate Avg Power Cutoff Display Instantaneous a Show Octave Details __ Fade Coherence B Compute Delay Figure 4 20 Transfer Function Controls Window 65 The Transfer Function 2 Click the Compute Delay button The Delay Finder window will appear 6068 Delay Finder PAA ae Maximum Channel Delay 32768 samples 743 039 ms 839 63 ft 252 90 m Make Capture Cursor 00 00 00 026961 Source Channel Delay 1189 samples 26 961 ms 30 47 ft 9 18 m Rename Window lt Q gt lt O Figure 4 21 Delay Finder window 3 The Delay Finder will automatically find the compensation delay and internally compensate the source signal The Delay Finder records 1 5 seconds of the source and response signal and computes the impulse response of the SUT The impulse response of a system is the signal that would come out of the SUT if you fed in an impulse An impulse is sort of like a clap or a snap but with an infinitely short duration of time The impulse response of a perfect wire is a spike the impulse offset by the propagation delay through the wire For a real acoustic SUT the impulse response will not be as simple as a spike The ti
141. ovides a mechanism for naming the input channels To access this mechanism simply click on the small lock icon 80 Controlling Audio and Instruments on the lower left hand corner of the Analyzer Control amp Routing window The window will expand to show the input channel names It looks like this O Analyzer Control amp Routing Analyzer 4096 Ft 10Hz Had d of Analyzer Channels 4 ES Input Matrix Output Matrix go Channel Names In 7 In F In a Reset Channel Hames ll Figure 5 10 Analyzer channel names You can type the proper input channel names into the edit text areas The lt tab gt key will move the input focus to the next field After you have named all of the channels that you are using click the lock icon again This will close the channel names and rename all of the channels within SpectraFoo If you want to hide the list of channel names you can click on the Channel Names disclosure arrow and the window will shrink down Now that your input channels are named and you have an easy way to refer to them you need to route the channels that you want to analyze to the analyzer This is accomplished with the routing portion of the Analyzer Control amp Routing window Each analyzer channel has a pop up menu associated with it This menu allows you to select the name of the input channel that you would like to send to the associated global analyzer channel O Analyzer Control amp Routing Analyzer 4
142. ow also contains the utilities to determine when a full scale sample is detected and how many consecutive full scale samples constitutes a clip Finally the Analyzer menu contains the command to show hide the Signal Generator Control of the Signal Generator is covered elsewhere in this documentation Audio I O Configure Hardware This item will open SpectraFoo s hardware setup window CoreAudio Device Configuration Select the CoreAudio device you would like to use CA Driver Built In 1 0 gt Sample Rate 44100 Buffer Size 256 AF 45 i maneal A Figure 11 4 Hardware Configuration Window e CA Driver The items in this menu will reflect any supported third party interfaces as well as the built in audio interface of your computer You may select which audio device SpectraFoo uses for analysis from here e Sample Rate You may select any sample rate that is supported by the interface selected by the CA Driver menu e Buffer Size This menu allows you to set the size of the CoreAudio buffer your interface will use in samples Larger buffer values will improve performance on slower machines at the expense of latency Smaller buffer values will improve SpectraFoo s analysis speed but require more processing power The buffer size also controls how much data certain instruments display in each update These instruments include the Oscilliscope Lissajous Phase Scope Code List Meter and the Bitscope The Monito
143. p Library entries These items make up the Group library Items can be added to or deleted from the library at any time The Real Time Rack SpectraFoo provides a two channel consolidated Real Time Rack view that contains all of the instruments in one convenient window When you use this view the Spectragram Spectragraph and Oscilloscope instru ments have linking buttons that allow you to either stereo link the control parameters between the left and right channel instruments or to link the control parameters of the Spectragram and Spectragraph of the same channel These linking buttons are very similar in concept to the link feature that appears on good quality stereo compressors For example the stereo link button on the Spectragraph allows you to ensure that both the left and right channel Spectragraph instruments use the same frequency calibration When instruments are stereo linked the parameters for both channels can be controlled from either the left or right channel details window These linking features are currently only available in the Real Time Rack consolidated view For the individual instruments available from the Master Controls window you can use the Link Group system described on the previous page for linking instruments 16 SpectraFoo Basics Lissajous Phase Scope Phase Torch Band Limited Phase Meter Timecode Clock Digital Level Meters L R Balance Meter Left Channel Oscilloscope Right Channel Oscilloscop
144. post delay time has elapsed The param eters sweep over the duration only So if the pre delay is 1 second the post delay is 1 second and the duration is 10 seconds the total loop time is 12 seconds The generator has two sweep modes The sweep mode is a global property of the signal generator the same mode is used for all sweeps You can set the mode for the generator with the sweep mode radio buttons Lin O Log Figure 8 3 Sweep mode radio buttons 1 The Lin button selects a linear parameter sweep With a linear sweep the sweepable parameters Power and Frequency change at a uniform rate As an example if the start frequency is 100 Hz the end frequency is 1100 Hz and the sweep time is 10 seconds the frequency will increase by 100 Hz every second 2 The Log button selects a exponential parameter sweep With an exponential sweep the sweepable parameters Power and Frequency change at an increasing rate This sort of sweep changes the fre quency a uniform number of octaves per second and the level a uniform number of dB per second As an example if the start frequency is 100 Hz the end frequency is 200 Hz and the sweep time is 2 seconds the frequency will increase by 1 2 octave every second Additive white noise with sweepable level In addition to the swept sine generators the signal generator also provides additive white noise The white noise generated by SpectraFoo has a uniform level pdf probability distributio
145. ptures 97 Automatic assembly of Split Stereo files 99 Automation 103 Capture List Window 99 Data slicing 104 Level based mode 97 Loading Audio Files 99 Loop points 101 Manual mode 97 Measuring time between two events 104 Overview windows 99 Ribbons 101 Timecode mode 99 Captures menu 109 Ask About Unsaved Captures 109 Delete Selected Captures 109 Load Capture 109 Save Selected Captures 109 Save Selected Captures As 109 Code List Meter 52 Code Matrix Meter 51 121 Code Meter 51 Correlation History Meter 50 Correlation Meter 49 D Data slicing 104 E Edit menu Edit Key Commands 107 Envelope History 44 F FFT 12 FFT window 96 File menu 107 Open 107 G Groups menu 109 Add to Group Library 109 Delete from Group Library 109 Instruments Adding and removing 76 Band Power History 49 Code List Meter 52 Code Matrix Meter 51 Code Meter 51 Correlation History Meter 50 Correlation Meter 49 Envelope History 44 Level meter 19 Lissajous Phase Scope 45 Oscilloscope 41 Phase Torch 47 Power Balance History 45 Power History 44 Spectragram 38 Spectragraph 25 THD Meter 53 Timecode Clock 49 Transfer Function 55 L Level calibration 84 Level meter Change Level based colors 25 Change Peak RMS VU colors 24 Change transition levels 25 Clip counter 20 Color modes 19 Index Color transition levels 25 Configure PPM ballistics 23 Meter bar colors 24
146. r To make this measurement we would hook the equalizer up like this Figure 4 16 Simple Measurement setup The signal source could be any source as long as it provides energy in the frequency bands that we are interested in If we wanted to measure the response of the equalizer from 20Hz to 20kHz a simple 1kHz sine wave would not be appropriate Good source signals are 1 Broadband musical sources These sources have the advantage that they exercise the SUT in a way that is consistent with the way that we expect to use the SUT 2 Pink Noise Pink noise has the benefit that on average it has a power spectrum that is consistent with most musical program material It also ensures that the entire audible bandwidth will be exercised Pink noise can be annoying when played over a Sound Reinforcement system but should not damage any system components e g high frequency drivers 3 White Noise White noise does not really match the characteristics of music but it does have a uniform density of energy in the entire audio band It can be used for testing electronic components but is very annoying when used in acoustic testing You also run the risk of damaging high frequency drivers if you play white noise through a sound reinforcement system at high SPL 4 Swept sines A sine sweep that covers the audio band to be tested will allow you to make an extremely precise highly noise rejecting measurement Swept sines do not bear any resemblance to
147. r Input command allows you to control how the software passes audio from its input to its output If this item is checked the audio will be passed If it is unchecked the audio will be muted If you are using 108 Quick Menu Reference the built in mic on a portable computer and are also using the built in speakers this item must be unchecked or you will encounter feedback The Use Internal Clock command allows you to choose between an internal and external clock source for the currently selected input hardware If the hardware supports changing the clock source this command will be enabled Generally you will want to use an external clock if you are recording or monitoring a digital input signal You may want to use the internal clock when you play material from a capture Captures The Captures menu is used to control the Capture List Window which is described elsewhere in this manual You can use the commands in the Captures menu to Load Save and Delete Captures You can also tell SpectraFoo to warn you if it is about to remove an unsaved capture from the system s memory The Save Selected Captures command will save all of the captures that are currently selected in the Capture List Window If any of the selected captures have not yet been saved to disk you will be prompted for a name and location to save the file The Save Selected Captures As command will allow you to save each of the currently selected in the Capture List Window
148. rating on is periodic That is it assumes that if the block of samples was to be repeated in a loop it would form a smooth and continuous repeating waveform of some kind Unfortunately music is neither completely periodic nor completely random If an FFT is performed on a group of samples taken from non periodic material spurious data results from the discontinuity at the boundary between the last sample and the first sample of the block Windowing helps to remove the spurious data by feathering the edges of the group of samples so that the group becomes periodic and continuous at the boundary The FFT Window Control Window allows you to adjust the shape of the windowing function used in SpectraFoo s FFT analyzer These adjustments can be done in real time allowing you to see their effects as they happen The Window Library pop up menu allows you to select from a set of preconfigured FFT windows and it also allows you to save your own windows for recall The FFT Window Control Window is accessed by using the Window Menu 96 10 Capture and Storage Recording Captures SpectraFoo provides the ability to record selections of audio into the computer s RAM and perform incredibly detailed non real time analysis All captures are referenced to the timecode of the source material Captures may be initiated manually or can be triggered automatically either with a level based trigger or a time based trigger The start and stop times for the
149. red stereo signal is e Correlation History a companion to the Correlation meter the Correlation History meter shows how the correlation is changing over time Dockable with the Correlation meter SpectraFoo Complete SpectraFoo Complete adds the following instruments to the Standard set e Code Meter Shows the per bit activity of the digital audio signal routed to the meter commonly known as a Bit Scope e Code Matrix Meter A unique meter designed to examine the upper 16 bits of a digital signal Allows you to quickly discover missing codes converter problems and code space utilization e Code List Meter A 1630 style display that shows the sequence of code values in the digital signal routed to the meter e Transfer Function Two channel differential FFT analyzer This instrument allows you to compare the spectral and phase content of two signals If the two signals are related part of a system the Transfer Function allows you to quickly discern the effect that the system has on the signals Coupled with the delay finder see below this is the critical tool for measuring the acoustic response of speakers and rooms It is also the primary tool for measuring the electrical response of signal processors You can also use the transfer function to analyze the difference between snapshots captured with the Spectragraph Instrument 18 Instruments e Delay Finder This instrument is used to measure the delay between the two analy
150. rface to the signal generator is numerical which makes it very precise but somewhat difficult to understand at first This release of the signal generator does not always do the right thing when you change the parameters while the generator is running Stopping and starting the generator will make it generate the proper signal The primary expected operational mode of the generator is using the system s sweeps to automate the signal parameters 0800 Signal Generator Sweep Type Lin O Log Ena Start Hz dB Phs End Hz db Post A jo pe jo o o jo jo jo O wi jo O Pi oo Current Sample Rate 44100 Peak Output inf dBFS _ Burst Time ms Burst Period Window Sample Rate Hz 44100 _ Synchronize Filer a E Save i sam e a ze 24 Bits Capture Dither oadd Pad Output by o dB a un 3 Figure 8 1 Signal Generator Control Window Sweepable sine waves This implementation of the Signal Generator supports up to 9 simultaneous sine sweeps at a time Each sweep is controlled with a cluster of parameters Ena Start Hz dB Phs End Hz Pre Dur Post 1000 jo ige E Je 600 Jo Figure 8 2 Sine Sweep Parameter Cluster 1 Enable checkbox Checking this box turns the corresponding sweep on in the signal generator 2 Start Frequency edit text box The frequency entered in this box is the frequency of the start of t
151. rument visibility position settings size routing etc A window set also captures all of the system level configuration details including analyzer depth global routing and global preferences Window sets are saved in the SpectraFoo preferences folder and are accessed from the Window Sets menu Each window set can also be assigned a key command for quick recall Finally you can specify what aspects of the saved configuration are recalled when you activate the window set If you make a habit of saving window sets whenever you create a useful instrument configuration you will rapidly increase the usefulness of SpectraFoo in your own work Parameter Management System SpectraFoo provides a complete parameter storage and retrieval library mechanism for all instruments in the system You can create named configurations for each of the various instruments and store them as presets There are two ways to save and recall presets 1 From the library pop up in an instrument s Controls window nm 5pectragraph Controls Save Parameters Save Parameters As Lename Current Fal Average Rate Avg Mode Log 4 Settling Time 2 039 Frequency Soo Power Scaling Frequency Range 0 Hz 17 42 kHz A I ee a lea 81631 62 125 250 300 ik k 16k Power Range SP Fanaa TTT 8 32 16 r0 6d 58 32 46 40 34 28 22 16 Figure 7 1 Accessing the library system from an instrument s controls window 85 Workflow Features 2 From the L
152. s simply select the number you want from the of Analyzer Channels pop up menu in the upper right hand corner of the Analyzer Control amp Routing window O Analyzer Control Routing o Analyzer 4096 Pt 10Hz TH Input Matrix Ana 1 Left 5 Ana 2 Right Mode gt Ana 3 ULN 2 Digit Ana 4 ULH 2 Digit G Mode 12 y Output Matrix 16 Out 1 Internal 1 HH out Internal 2 24 Qut3 nic ey Gutd nic Channel Names Reset Channel Names Figure 5 7 Changing the number of analyzer channels SpectraFoo needs to restart in order to change the number of analysis channels When you change the number of analyzer channels you will be presented with a dialog confirming that you want to restart SpectraFoo 79 Controlling Audio and Instruments You must quit and restart the application to change the number of analyzer channels Do YOU Want to quit now C Cancel Qui li ll Figure 5 8 Restart to reset analyzer channels If you hit Cancel the number of channels will return to its previous setting If you click the Quit button Spec traFoo will quit To restart it double click on the SpectraFoo application SpectraFoo will restart with the newly selected number of analyzer channels The number of analyzer channels is saved as a preference so SpectraFoo will remember the number of analyzer channels each time it is started Changing the analysis depth You can change the number
153. s commonly used for K meters When unchecked the color tran sitions fade from one to the next Color Transition sliders The Safe Until Caution Level and Danger Level slid ers set the dbFS level at which color transitions will occur In the figure above a signal will be displayed as green until 30 db turn yellow from 30 to 18 dB and is red over 18 dB You may change the colors by clicking the color wells at the left end of the slid ers Peak RMS VU color wells These allow you to set the colors for the Peak RMS and VU indicators PPM ballistics The Level Meter can be set to use PPM decay or to provide instantaneous digital metering with no crawlback In order to operate as a traditional Peak Program Meter you must configure the meters to use PPM ballistics and choose the standard crawlback speed This is the default configuration for the meters You can also choose non standard crawlback speeds to make the meters more responsive or to provide a longer persistance time choose the settings that work best for you To configure a Level Meter to use PPM ballistics 1 Open the Level Meter controls window and click the Options button The Level Meter Options win dow will appear 23 Instruments mn Level Meter Options YU Settling Time 0 2435 PPH Settling Time 1 70 s u PPH Peak Float Size 4 Hold Release Time 2 00 s Meter Scaling Tick Spacing 3 00d6 Scale Type SpectraFoo H EJ Use Level Based Color E
154. se or pop music Classical music does not work as well You must also ensure that the source is louder on average than the environmental noise Make sure that you are getting both the source and response signal into Foo You can use a level meter instrument to make sure that you are getting signal Check to see that the input levels of the two signals are reasonably equal in level You can eyeball this with the level meter or you can use a power balance meter to balance the input levels Adjust the Avg Power Cutoff slider in the Transfer Function Controls window so that the pointer is in the middle This will allow you to get an accurate time delay calculation Click the Compute Delay button The Delay Finder will appear and automatically compensate for the acoustic delay Adjust the Avg Power Cutoff slider in the Transfer Function Controls window so that the pointer is near the left hand end of the slider This will help the MBM thresholding system reject environmental noise If the traces are not moving at all select Age from the Fade pop up menu Ensure that the traces are flashing bright green all over the entire audio bandwidth If they are not decrease the Avg Power Cutoff slider until the traces start flashing You do not want the trace to be completely bright green just flashing Adjust the Avg Rate slider so the pointer is near the middle of the slider This will cause the Transfer Function to average over a reason
155. set on the audio hard ware Always run at full speed When checked SpectraFoo will update the dis plays as fast as possible even when it is in the back ground When not checked SpectraFoo will throttle back display updates to 10 frames per second when it is in the background All changes that you make with this control panel are remembered as preferences These changes take place immediately 106 Quick Menu Reference File The Open command allows you to open compatible sound files on your computer as Captures No other items in this menu are used by SpectraFoo To save your analysis settings please see the information on Windowsets Edit The Edit Key Commands menu item allows you to view or change the key commands for many standard menu commands Command Keys Command Key Command Hide Show Window Sets Window HAY Update Current Window Set e LU Save Window Set As oA Hide Show Link Groups Window eG Rename Current Window Set UR Close All Documents a LW Close All Floating Windows eat TW Close Front Floating Window de ut Wi Toggle Front Instrument Power p Toggle Front Instrument Solo 0 Toggle Front Instrument Controls AA Hide Show Command Keys Window WAZ Signal Generator Toggle Run Stop G Signal Generator Toggle Visibility En Figure 11 2 Key Commands window Legend e 3 Command e Option e Control e Shift To change the default key command double click the command name to open the K
156. slider that makes the measurement much more responsive For very noisy acoustic environments you need a slower averaging rate closer to the right hand side of the slider so that you average over more time For most acoustic environments the middle of the slider is a good starting point but you will need to adjust this parameter on a case by case basis Avg Power Cutoff Slider You use this slider to control threshold level applied to the spectrum of the source signal When the source signal level is higher than the threshold this is computed for every spectral line in the spectrum the transfer function adds the measurement to the average If the level is below the threshold the data is ignored You can see which bands are above the threshold level by setting the Fade pop up menu to Age For every band that is above threshold the response curves will be drawn in bright green For normal 59 The Transfer Function acoustic testing you want the response curves to be flashing on and off not a constant bright green and not a constant dark green This allows the MBM thresholding to reject environmental noise the best Display pop up menu This pop up menu allows you to choose what data is displayed in the transfer function window 1 Instantaneous This mode displays each instantaneous measurement of the transfer function 2 Average This mode displays the thresholded average of the transfer function data Fade pop up menu
157. tage of the total power present in both signals The light grey lines appear once per second as the history scrolls to the left This meter is very helpful for precisely identifying the aspects of mixes that don t have a natural flow of energy between the left and right channels It is also great for power balancing natural stereo recordings and two channel measurements of equipment Lissajous Phase Scope Vectorscope and X Y modes The Lissajous Phase Scope is equivalent to an oscilloscope running in either vectorscope or X Y mode Figure 3 50 Lissajous Phase Scope X Y mode 45 Instruments or stereo position mode You can switch the mode by opening the Controls window and selecting the appro priate mode with the Scope Mode pop up menu This tool shows you the amplitude of the first input signal versus the amplitude of the second input channel signal This instantly lets you know if a mix has polarity problems It also allows you to see the width of the stereo field of the material being monitored When the scope is in vector mode in phase material appears as a vertical line while out of phase material appears hor izontal When the scope is in X Y mode and the activity of the trace occurs mostly in the lower left and upper right quadrants of the display as pictured the left and right channels are predominantly in polarity When the activity of the trace occurs mostly in the lower right and upper left quadrants of the display the l
158. than the unmodified version of hardware and software with which the Software was designed to be used as described in the documentation Any failure of Licensee to comply with this provision is a material breach of this Agreement Licensee agrees that it will not attempt to alter disassemble decrypt or reverse engineer the Software 2 EXPORT LAW ASSURANCES Licensee acknowledges that the laws and regulations of the United States restrict the export and re export of commodities and technical data of United States origin including the Software Licensee agrees that it will not export or re export the Software in any form without the appropriate United States and foreign government licenses Licensee agrees that its obligations pursuant to this section shall survive and continue after any ter mination or expiration of rights under this Agreement In any event the Licensee may not export or re export the subject Software without the express written permission of MH 3 TRANSFER OF LICENSE Licensee is permitted to transfer this license of the Software and all rights under this agreement to a third party only after the Software has been removed from the computer on which it was installed The Licensee must request a license transfer from Metric Halo Laboratories Inc prior to the transfer of the Software In the event that the license is transferred and or exported or re exported to the extent permitted by this Agreement any such transferee must agree
159. that there are a series of closely spaced notches in the high end of the system response 8 kHz and up These correspond to reflection nulls that will move around when the microphone position is changed but 72 The Transfer Function will not disappear They will make the system sound ragged on the high end and will also make the system sound phase y when the listener moves around These are caused by acoustic reflections and are best treated with diffusion or absorptive material We can now try to correct the system with equalization What we want to do is adjust the system EQ to match the inverse of the system response When we do this we will pre compensate the signal sent to the sound reinforcement system so that when it applies its effective equalization to the signal the result balances out and leaves us with a relatively flat system response System Correction 1 Switch the response signal source to be the output of the system equalizer 2 In the Overlays window click the checkbox in the V column of the transfer function overlay that corresponds to the system response that you want to correct This makes the snapshot visible in the Transfer Function window Make sure that the I checkbox is also checked This Inverts the snapshot which makes it look like the EQ curve that we need to correct the system The overlay is displayed in the color of the tile next to the snapshot name If you want to change this color clic
160. the speed of sound V the response at the microphone will have a null for frequencies where n is any integer as shown in this equation _ Y al Figure 4 28 Null for frequencies This is just a simple comb In any real acoustic environment there will be many reflective surfaces with many different reflectivities and phase shifts so we will not see a simple comb filter but a complex set of partial nulls At the partial nulls in the response at microphone position little of the source signal will be detected only the environmental noise will be measured This means that at the nulled frequencies the coherence will be very low 69 The Transfer Function This provides us with the key to understanding how to use the coherence The coherence tells us where the measurement that we have made is valid It is basically a measure of the quality of the measurement at the corresponding frequency In terms of correcting the response of acoustic systems the coherence tells us which notches or dips in the response curve are Equalizable and which are due to nulls in the measurement If the coherence is low at a dip in the response curve we will not be able to use an equalizer to fix it If the null is due to the specific position of the measurement microphone we can generate a better averaged response by making measurements at a variety of microphone positions and then averaging the measurements This technique is described in more detail later On
161. ther to make them time aligned Data Slicing When Data Slicing is enabled the instruments display the data which lies underneath the current position of the cursor The grey area around the cursor represents the range of samples currently displayed by the realtime instruments If you drag the cursor around in the overview window the instruments will continuously update to reflect the current cursor position If you replay the capture the instruments will continuously update in sync with the playback AOA Overview WS aif Capture Name WS aif Start 00 00 00 000000 Length 00 04 14 577755 M Draw Dual Trace 00 04 14 577755 or tes lt v Do Data Slicing gt Details gt Calibration KG 00 00 00 000000 2 00 04 14 577777 A 00 04 14 577777 Ribbons Envelope Spectral History lt Window Start Window End gt SpectraFoo 0 ee mMm es 7X 8H 87 E Figure 10 28 Data slicing 104 11 Quick Menu Reference Main The Preferences command allows you to bring up system wide preferences for SpectraFoo These preferences allow you to control the visual appearance of the components of SpectraFoo along with some aspects of its operation Py Preferences _ Panel Color M Use brushed metal panels Panel Highlight Tints C Instrument Windows Have Window Frames Font Lucida Grande E All clicks bring instruments to front Ed Use 64 bit Analyzer on next launch FFT depth change Ed Automatically
162. tion without delay compensation tasas cnondeasamnau cease tedcveweeaceaetins 65 420 raster Funcion Controls VVINCOW estatales 65 M2s Dely R nder WNION O aartahauk on areas E ences cl oented arse cncrcnl acest 66 422 AME AWSMEO rans eranc si iia 67 423 Conerence expressea MAtNEIMGUGAIIY isla ibid 68 424 Simple source and FESO GIMSE SIO MAIS tia iaa io ta lid 68 425 Simple source Complex response signal o ias 68 A 76 ACUS Cte t WIth reected patis nieta 69 A A EEE EA A E E EE E 69 SpectraFoo User s Guide AO NGIL TOR MEQUEencies rito 69 4 29 Measurement ano Correci n Setup us 70 a o A lint 71 AD ranster TURCUOR Overlay ES asas 72 AZ ample ranster UNCON an conos 72 4 33 Transfer Function Snapshot Overlays window alzado tl sida 74 43d ranster TUncHonsmapshat ealtidialos strain tada dci dnS 74 4 35 Mini menu window command pop down Menu oococccnnccnnccnnccnnncnnnncnnncnnnccnnncnnncnnnncnnncnnncnnncnnanoss 75 ANa CONTOS ROUNE opi 76 52 Master CONO WINCOW sagens aoa E T E E pls 76 5 ASUMEN removal WINdOW a a a a a 77 se ED O mena EE E E tin naa A E E E A E E E 77 5b cally Zen Controlled ROUNE VVINCOW vai 77 Anal zericha Ane TOUNE Terreur E E espiss 78 5 7 Changing the number of analyzer channels scada dali 79 KOs REStarto TESel an aly Zer CMANNEIS anaE te wala aes laacw eon dehe wien eatanaeacietanu steal a edalare ice 80 IC hane Ne the anal sis dep iii 80 Duals Analyzer Channel Mames plana reads 81 Sala Named
163. traFoo It just means that your machine might not support 24 channels of simultaneous analysis If you are interested in determining the upper limit of your computer s multichannel analysis capability you should start SpectraFoo at a non critical time and step up the channel depth from the 2 channel default setting to six channels then to 8 and so on Of course it makes no sense to increase the number of analysis channels to be greater than the number of hardware channels that are available Each time you change the analyzer depth evaluate the performance of the analysis instruments When the update of the instruments begins to get sluggish it is an indication that you are beginning to overtax your host processor On some slower machines it is possible that 2 analyzer channels will be the maximum that is practical Adjusting the Number of Analyzer Channels You can adjust the number of channels of simultaneous analysis available in SpectraFoo There is a small trade off between the number of channels and overall system performance The more channels of analysis that you have the more the system is loaded down For best performance leave the number of channels in the 4 8 region If you have a need to analyze more channels by all means do so but don t set the number of analyzer channels to a large number arbitrarily you will get better performance by selecting the number of channels that you actually need To change the number of analysis channel
164. umns Each time the display is updated all of the samples in the time slice are shown The number of samples in the time slice are determined by the I O hardware s buffer size The samples are displayed starting with the first sample in the time slice in the upper left hand corner of the instrument Each successive sample is place under the previous one until the bottom of the column is reached The next sample is placed at the top of the next column So in the figure below the samples 1 64 are in column 1 65 128 are in column 2 and so on with samples 449 512 in column 8 The layout of the bits in each sample are shown below Bit 123456789 IO Tl 1213 1415 1617 18 19 20 21 22 23 24 Sample 2 3 4 Figure 3 69 Bit Layout in Bit Scope THD Meter The THD Meter is used to measure the noise and distortion performance of audio equipment 1 Frequency Locked 1000 62 Hz S N D 0 003175 89 966 dBr 100 284 dBFS HD N 0 000366 108 723 dBr 120 801 dBFS Otal 15 078 dBFS Figure 3 70 THD Meter To select the audio channel to analyze hold the control key and click the parameter control button 53 Instruments Figure 3 71 Parameter control button The Frequency Locked indicator will come on when the THD Meter senses a single frequency signal and will display the frequency e The S N D display shows the signal to noise plus distortion measurement e The THD N display shows t
165. ure window to zoom out Option clicking this button decreases the number of data points used to compute the FFT for the Spectral History ribbon Figure 10 21 Zoom In Clicking this button causes the capture window to zoom in Option clicking this button increases the number of data points used to compute the FFT for the Spectral History ribbon NN Figure 10 22 Cursor Clicking this button selects the cursor tool Figure 10 23 Automation point movement tool Clicking this button selects the tool that allows you to move automation points Figure 10 24 Automation point pencil tool Clicking this button selects the pencil which allows you to create automation points Holding the Command key turns this into an eraser to remove automation points Figure 10 25 Automation mode This button toggles the volume automation on and off When automation is on you may draw volume break point automation for capture playback The ribbons will will show the original waveform overlaid with the waveform as modified by the automation data Figure 10 26 Loop crossfade The crossfade button controls whether or not loop playback is cross faded If the it is turned on the loop engine will crossfade between the end of the loop and the beginning of the loop If it is off there is no crossfade e Zoom scrollbar This scrollbar lets you change the zoom level of the window e Window scrollbar This scrollbar shifts the audio through the window Each t
166. usical instrument with multiple microphones You can use the Phase Torch to identify the frequency ranges in which phase cancellations are occurring as a result of the comb 47 Instruments filter created by the use of multiple mics on a single source Phase points that are oriented on the negative Y axis of the meter represent the null points of the comb filter This can help set up multiple microphone placements that create nulls which are outside of the critical frequency range of the instrument you are recording The Phase Torch can can also be used as a very quick and elegant troubleshooting tool for identifying phase anomalies in studio wiring If you suspect a phase compensation or delay problem between multiple audio paths in your studio simply run a common signal into two paths and route one to SpectraFoo s left input and the other to its right input If a phase problem exists the Phase Torch will display it immediately The Phase Torch is also effective for a number of other applications including e Setting azimuth on analog tape recorders Checking for time alignment in complex PA systems e Identifying frequency dependent phase and polarity problems such as an out of polarity high frequency driver in a sound reinforcement system e Frequency sensitive mono compatibility analysis The Phase Torch controls window has a threshold slider which allows you to set a level threshold for the meter O Phase Jorch Controls Factory D
167. will only display channel 1 Sum Multiply and Overlap modes You use the Spectragraph Controls window to display and control second traces The second trace in a dual trace Spectragraph can represent the second input channel as in the examples above or one may be set to one of the following e None This does not draw a second trace e Channel 2 This draws the Channel 2 selection as the second trace e 1 2 The sum of the two channels routed to the Spectragraph This shows the sum total power in the stereo signal e 1 2 3 dB The sum of the two channels routed to the Spectragraph 3 dB This shows the average total power in the stereo signal e 1 2 The product of the two channels routed to the Spectragraph This filters the power of one signal with the power of the other e sqrt 1 2 The square root of the product of the two channels routed to the Spectragraph This shows the overlap of the power in the two signals 27 Instruments a Spectragraph Controls Channel 1 st None Bl 2 5734 15 Channel 2 Use dBu Calib Accumulation Mo l 2 Resolution col 1 2 3dE Reset Peak Holds Show Traces PASA mC t Peak sgrr 1 2 EA 1 Imstant m Second Traces 2 Peak IA m wi 2 Instant Rate Avg Mode Log he Settling Time Tsar sS Frequency coh Power Scaling Frequency Range 0 Hz 16 10 kHz ea seeds 81631 62 125 ik k de Spec Wena T Ap 20 82 76 70 64 58 52
168. y can also help you determine whether the compressor should be set to react to Peak or RMS levels Figure 3 46 Power history Note This meter is scaled logarithmically in decibels When the average level is high the signal can change relatively dramatically in level without creating a large change in the display In this situation it is useful to refer to the envelope history display which is described below Envelope History This instrument is a sample editor style scrolling envelope overview It can help you calibrate your eyes if you are experienced with DAW style displays Because it uses linear scaling it is useful for identifying large level changes when the average level is high It should be used in conjunction with the Peak and Average History display to obtain a good view of the overall dynamics of program material Figure 3 47 Envelope history 44 Instruments Power Balance History Figure 3 48 Power Balance History The Power Balance History compares the power balance between the two input channels as a function of time When the power level on the first input channel is greater than the second input channel the display turns green and shifts above the centerline When the power level on the second input channel is greater than the first input channel the display turns red and shifts below the centerline The length of the indicator expresses the difference in power between the right and left sides as a percen
169. y signals like pink and white noise even if the source and response are somewhat unsynchronized the power measurement will be pretty good but the phase measurement is useless Figure 4 18 Acoustic test setup Under normal circumstances the response signal will always be delayed from the source signal Sometimes this delay can be very short for example if the signal source is external and the SUT is analog and contains no acoustic elements the delay can be less than a sample If the SUT contains acoustic elements like a speaker there is always the acoustic propagation delay In any case the delay must be compensated to achieve an accurate measurement When we make a typical acoustic measurement we are measuring all of the elements that are not common between the source path and the response path In the case illustrated above the speaker speaker amplifier acoustic space measurement microphone and preamp are not common The amplifier speaker and acoustic 64 The Transfer Function space are the elements that we want to measure The microphone and preamp are not In order to eliminate the pre amp from the measurement we can pass the source signal through the same type of preamp or we can use a preamp that is flat the LAB preamps from Earthworks are good for this purpose We cannot eliminate the effect of the microphone but we can reduce it by using a quality measurement microphone Once again Earthworks comes to the rescue wit
170. y to this Agreement IF YOU DO NOT AGREE TO THE TERMS OF THIS AGREEMENT PROMPTLY RETURN THE MEDIA ON WHICH THE SOFTWARE IS FURNISHED WRITTEN MATERIALS HARDWARE IF ANY AND OTHER ITEMS WHICH ARE PART OF THIS PRODUCT TO THE PLACE WHERE YOU OBTAINED THEM FOR A FULL REFUND This legal document is an agreement between you the user Licensee and Metric Halo Distribution Inc hereinafter MH Licensor LICENSEE ACKNOWLEDGES HAVING READ UNDERSTOOD AND AGREES TO BECOME BOUND BY THE TERMS OF THIS AGREEMENT WHICH INCLUDES THE SOFTWARE LICENSE LIMITED WARRANTY EXCLUSIONS OF LIABILITY AND PROPERTY RIGHTS OF THE LICENSOR 1 SOFTWARE LICENSE TERMS Licensee agrees to install and use the Software on one 1 computer at a time The Software may not be networked The Software may not be duplicated or reproduced in any form whatsoever except as required to execute the software on the licensed machine Any required additional copies can be purchased directly from MH or its authorized distributor Further if any modifications are made to the Software by Licensee during the warranty period if the media is subjected to accident abuse or improper use or if Licensee violates the terms of this Agreement then the warranty shall immediately terminate and MH shall have no responsibility to replace the Software or refund the purchase price Moreover this warranty shall not apply if the Software is used on or in conjunction with hardware or software other
171. you have opened a Capture Overview window by double clicking on one of your captures in the capture list window you can examine various timecode locked historical representations of the capture including the 99 Capture and Storage envelope the power balance the peak and average level and the spectral power history You can slice the capture at any instant of time to display the instrument analysis of the signal at that instant in all of the real time instruments Understanding the Overview Window 800 Overview 05 Equinox aif Start 00 00 00 000000 Length 00 06 55 817317 _ Draw Dual Trace End 00 06 55 817317 Cursor 00 00 41 141619 lq i _ Do Data Slicing 0 06 55 817333 A 00 06 55 817333 Capture Name 05 Equinox aif Y Details Y Calibration 00 00 00 000000 0 Left 6 92 0 73 Right 5 99 1 97 Balance L 7 Peak L 23 20d8 RMS L 27 36dB Peak R 24 46dB RMS R 27 96dB P f L LF 2 06 kHz HF 2 22 kHz 93 50dB P f R LF 2 06 kHz ill lc l ei 1 i Corr 0 20 00 00 39 716875 Ribbons Envelope Power Balance Power History Spectral History Correlation History lt 00 00 54 071041 Window Start Window End m ib aereos E zr gt Figure 10 5 The Capture Overview Window There are many controls and data fields in the Capture Overview Window let s break it down into the top ribbons and bottom Capture Name 05 Equinoxaif
172. zation 93 Output Routing 83 Pink noise 92 Selecting the rectangular analyzer window 93 Sweep modes 91 Sweeps 90 White noise 91 Windowed Bursts 94 Spectragram 38 Orientation 39 Preferences 40 Spectragraph Accumulation modes 28 Assign and display a spectral snapshot 35 Change trace colors 30 Create a Transfer Function from two Spectral Snap shots 37 Create average snapshot 36 Dual channel modes 26 Log and linear averaging 33 Octave Analysis 30 Physical unit calibration 29 Spectral Snapshots Overlays amp Libraries 33 Sum Multiply and Overlap modes 27 Taking a spectral snapshot 33 Trace colors 30 Sum amp Difference monitoring 82 System Requirements 12 T THD Meter 53 Timecode Clock 49 Transfer Function 55 About the Response Curves 70 Checking your measurement equipment 63 Coherence 60 67 Controls 58 Cursors in the Transfer Function window 75 Interpreting the Data 67 Measuring system response 71 122 Index Overview 55 Snapshot Overlays Reference 73 System Correction 73 Time align the source and response signals 65 Transfer Function Window 60 Understanding the Transfer Function 62 Working with extremely long delays 66 W Window menu 109 Window Sets 85 86 Creating 86 Modifying 87 123
173. zer channels used by the Transfer Function It does this by computing the impulse response of the linear transfer function that relates the response channel to the source channel After computing the impulse response the delay finder automatically compensates for the delay by inserting additional delay internally on the source channel so that both channels line up You can use the delay finder tool to choose a different alignment delay e THD Meter This instrument provides S N and THD measurements These instruments are discussed in detail on the following pages This instrument reference section details the appearance and function of the instruments as well as the controllable parameters that you can use to adjust the functions of the instruments Level Meter Overview This instrument provides a highly configurable two channel three in one digital level meter Like all Spec traFoo instruments the level meters are resizable If you make the meter wider than it is tall it will use a horizontal orientation Figure 3 1 Level Meter Horizontal Orientation If you make it taller than it is wide the meter will use a vertical orientation Figure 3 2 Level Meter Vertical Orientation SpectraFoo s Level Meters allow you to switch on the fly between modern fast tracking sample accurate digital ballistics and traditional standards based PPM ballistics Many engineers are used to working with PPM standard hardware level meters

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