Technical manual
Contents
1. 11 8 Shared electronics example 2 1 12 9 Listening area definition a 13 10 Interferences between columns 15 11 StepArray directivity control with the NUT software 16 12 Examples of a CAD modeling results 17 13 Column mounting on a wall 22 42 2445 4Hb eee ras a a 20 14 NUT to MPA6150 wiring xo ozono ii ara 21 15 MPA6150 amplifier set up 21 TE MPAGISOIO SOI WIN sos i saskes SES Ongir e LER LGR ee Re we a ai 22 17 StepArray column dimensions 26 18 Fixing brackets for wall mounting of StepArray columns 27 19 Frequency response column SA250P 2 a 2 28 20 Horizontal directivity column SA250P 28 21 SA100P acoustical data a A 29 22 SA180P acoustical data 5 amp E as we 30 23 SA250P acoustical data ee 0 31 24 SA400P acoustical data 32 25 SA180S acoustical data LL sit er aa A LA Reese 33 26 SA250S acoustical data 4 o ar a su ma EA es Dig eae 34 36 www activeaudio fr info activeaudio fr 332 Bd Marcel Paul CP602 44806 Saint Herblain Cedex France Tel 33 0 2 404 666 64 Contact2. Table 1 General characteristics of StepArray columns StepArray columns do not use opening angle and tilting angle to tune directivity Instead StepArray use the listen ing area definition to automatically adjust themselves as to fit the requirements to the best Y f A SY StepArray columns use the listening area definition to automatically adjust themselves The StepArray range provides a full set of listening ranges and audience tilting angles to suit any public address situation The listening areas as described on figure 9 on the facing page are listed on table 2 on the next page The nominal situation corresponds to the conditions for which the column has been designed By specifying the 8The horizontal opening angle corresponds to a 6dB attenuation for the average of the 1 kHz and 2 kHz octaves The range of a column is defined as the maximum distance from the column for which the mean sound level for the octaves 500Hz 1 kHz and 2 kHz remains within 3dB or 5dB 12 V audio 3 2 NUT processor effective positioning of the column and the shape of the listening area in the StepArray bloc of the NUT control software the DSP filtering parameters are automatically adjusted to the situation Choose the column which covers the most of the listening area 1 s of i s i oo i i st ss ee ween min
3. Figure 9 Listening area definition Nominal altitude h Audience Range 500Hz 2kHz Min distance Channel standing seated audience angle 0 3dB 5dB dinir count SA100P 2 5m 2 1m Flat 0 5 15m 21m SA180P 2 5m 2 1m Flat 0 5 30m 40m Sa2sop 25m 25m 2 m Faos amam m 6 SAdo0P am S0m 26m Faos 6am 90m im 6 sazsos 25m 42m 58m Tited 5 20 2m d m dm 6 Table 2 Specific characteristics of StepArray column models 3 2 NUT processor The NUT processor has 8 output channels therefore it can deliver signals for two 3 channel columns or one 6 channel column It is also possible to connect two 3 channel columns with different signals on the same processor to obtain a stereo sound Independent settings are available for directivity equalization and delays All these settings can be saved and recalled remotely thanks to presets More details on wiring can be found in section 8 1 3 3 MPA6150 amplifier The MPA6150 amplifier can deliver 6 x 150 watts under 482 load or 6 x 100 watts under 81 loads It is the standard amplifier used to drive StepArray columns but any other amplifier with similar power capabilities can be used with StepArray columns More details on wiring can be found in section 8 1 Last update October 10 2014 13 V audio 3 4 Cables 3 4 Cables Cable lengths detailed in table 3 correspond to the maximum lengths recommended for the amplifier to
4. Therefore in large and reverberant rooms the most important parameter the public address must affect is the Direct Sound Reverberated Sound part of sound This can be achieved either by moving the loudspeaker close to the listener or by using highly ratio It is necessary to privilege the direct sound energy and avoid putting energy in the reverberated directional loudspeakers In a large and highly reverberant room it is necessary to privilege the direct sound energy for good 7 intelligibility results In large spaces if the loudspeakers are to be placed close to the listeners many loudspeakers are required This is not practical in such places because fixing loudspeakers can be difficult very high ceiling etc Also in many cases this will not give good intelligibility results because only the loudspeakers close to the listener contribute to the direct sound while all the loudspeakers contribute equally to the reverberated sound Several indexes have been proposed to measure speech intelligibility The most widely used of them is the Speech Transmission Index STI Value 0 corresponds to extremely poor intelligibility and value 1 corresponds to perfect intelligibility It is generally considered that intelligibility is correct above STI 0 55 2 Energy of the reverberated field is proportionnal to the ratio feverberation time Room volume V audio 1 2 Loudspeaker arrays Using many non directional loudspeakers ofte
5. b SA250S horizontal directivity sound level for the voice octaves 500Hz 1kHz 2kHz on the listening plane SPL dist SA250S 15 250Hz 500Hz 10 1000Hz 2000Hz 4000Hz 8000Hz 15 0 5 10 15 20 25 30 c Sound level by octave in the axis of the listening plane in front of the column with respect to the distance from the column Figure 26 SA250S acoustical data 12 Column is in nominal position Levels are referenced to the mean SPL on the listening area 34 Gente LIST OF TABLES List of Tables 1 General characteristics of StepArray columns 2 a a a a a a a a 12 2 Specific characteristics of StepArray column models 13 3 Wiring recommendations for StepArray columns 14 5 DC resistance of StepArray columns a a a a a 26 6 Mechanical and electrical characteristics of StepArray columns 27 Last update October 10 2014 35 Gente LIST OF FIGURES List of Figures 1 Direct sound increases speech intelligibility reverberated sound impairs it 5 2 J shape wave front lt 2c awe wee bebe de se be des REGE EMA EEE EEE BA A 7 3 Electronic and geometric arrays 0 8 4 DGRC BMC css Rai Lei RL de Ladder ed RENNES REA A Ed eau 9 5 Example of StepArray system 0 10 6 Listening zones P models a a a a a 11 7 Listening zones S models
6. 6 channel column one or two 3 channel columns Moreover a NUT processor can be connected to one or several StepArray amplifiers to feed several columns with the same signal In this case the inputs are simply daisy chained to the amplifiers see section 8 1 on page 21 In the example installation figure 8 on the following page three independant rooms are equipped with StepArray columns Each room receives its own signal and can have independant parameters For a total of 6 columns only 2 processors and 3 amplifiers are needed Last update October 10 2014 11 Active audio Lounge 2 x SA100P Conference room 2 x SA180S Hall 2 x SA250P SUB gt gt 3x MPA6150 2x NUT BEEN Lounge input Conference input Hall input Figure 8 Shared electronics example 3 Choosing the right installation set up 3 1 Columns All StepArray columns feature a large frequency bandwidth and a wide horizontal opening angle The columns are mounted vertically using the supplied square brackets The columns are available in standard RAL colors RAL9016 and RAL9005 but any other RAL color is available with the COL option Table 1 sums up these charac teristics Max SPL Bandwidth Mounting Colors 95dBspL 135Hz 17kHz 3dB Vertical White RAL9016 pink noise 110Hz 19kHz 10dB supplied Black RAL9005 in listening area square brackets Any RAL COL option
7. bottom bracket only Figure 18 Fixing brackets for wall mounting of StepArray columns Last update October 10 2014 27 13 Acoustical data All data presented below is obtained with columns in their nominal position and using nominal DSP filtering param eters flat EQ etc 13 1 Common data amplitude dB 10 10 10 frequency Hz Figure 19 Frequency response column SA250P Average of the mesurements at 7 10 15 20 25 and 30m In red with bass high pass on position 100Hz in blue with bass high pass on position 200Hz 500Hz 1kHz 2kHz 4kHz 8kHz 60 300 Figure 20 Horizontal directivity column SA250P 28 V audio 13 2 SA100P acoustical data 13 2 SA100P acoustical data 100B 10dB J 10m 20m b SA100P horizontal directivity sound level for the voice octaves 500Hz 1kHz 2kHz on the listening plane SPL dist SA100P 15 T 250Hz 500Hz 10 1000Hz 2000Hz 4000Hz 8000Hz 15 0 2 4 6 8 10 12 14 16 18 20 c Sound level by octave in the axis of the listening plane in front of the column with respect to the distance from the column Figure 21 SA100P acoustical data Column is in nominal position Levels are referenced to the mean SPL on the listening area Last update October 10 2014 29 V audio 13 3 SA180P acoustical data 13 3 SA180P acoustical data 100B 10dB 3 10m 20m 30m 40m b SA180P horizontal d
8. installation The audio signal is fed into the NUT processors which then supply DGRC compatible signals to the MPA6150 amplifiers driving StepArray columns A NUT processor also provides sub bass output for an active subwoofer The settings are made with the NUT control software through an Ethernet cable here but a USB connexion is also available 4x SA100P SA250P SA250P 2x NUT HEEE eo mm i E OQ_ Ethernet Audio input Figure 5 Example of StepArray system 2 2 StepArray column models Table 1 on page 12 and table 2 on page 13 give an overview of the StepArray models characteristics A complete description of the technical characteristics can be found in sections 12 and 13 10 V audio 2 3 StepArray specificity shared electronics 30m Floor Figure 6 Listening zones P models 4m 22m 28m Figure 7 Listening zones S models Columns whose name ends with a P SA100P for example are designed for horizontal audience areas whereas column whose name ends with a S are designed for tilted audience areas or with balcony 2 3 StepArray specificity shared electronics One of the advantages of using external electronics is that several columns can be connected via their amplifier to the same NUT processor A NUT processor features 8 analog symmetrical outputs Therefore a single NUT processor can be used to deliver signals for e a
9. reference describing the full range of StepArray products It covers installa tion wiring maintenance and tuning Extensive technical data is found there Last update October 10 2014 3 Aline audio Part StepArray tutorial for recommandation Table of Contents 1 Sound reinforcement in large spaces 1 1 General issues with public address in large spaces ee L2 LOM ANDO coser ecards 1 3 DGRC The StepArray system 4 666 6s eke eed RA Ee 2 Overview of the StepArray system 2 1 StepArray system example 22 Ma CONAN models s i so eRe hee a sa EER ORES Eee LR ee 2 3 StepArray specificity shared electronics 3 Choosing the right installation set up ok SOM oo a as A eS AAA AAA coe NUT MOO socias AAA a PAPA ee Li AAA ESA TE KSEE EES a OM RR aerea rodas eS oe aaa Oe AS Fs A se re ee oS OS Eee E ES es ee E 4 Column positionning rules 5 NUT processor and control software 6 CAD modeling References Oo N Ot ON 14 16 16 17 Active audio Introduction This is a tutorial for StepArray recommandation Section 1 presents general issues about public address in large spaces 1 1 and explains how loudspeaker arrays can be a good solution to these issues 1 2 StepArray is introduced as the last point of this section 1 3 The following parts are a step by step introduction to the StepArray system Section 3 exp
10. the room In contrast high speech intelligibility can be obtained with a limited number of loudspeaker arrays often only 1 or 2 in a large and highly reverberant room with minimum impact on the aesthetics of the room It is easy to calculate the shape of the wave front that should be radiated by a loudspeaker array in order to yield constant SPL over the entire audience area and minimize sound energy emitted elsewhere A J shape wave front is obtained in which the local curvature depends on the focal distance as illustrated on figure 2 In order to generate such a wave front one can align loudspeakers along the J shape as in geometric arrays figure 3a on the following page C HEIL or place loudspeakers on a vertical line and rely on the filtering of each individual loudspeaker as in electronic arrays figure 3b on the next page DSP directivity The latter case corresponds to column loudspeakers which can be flush mounted on a wall Advantages and disadvantages of both array types are discussed in DGRC Arrays X1 Listening plan X2 Figure 2 J shape wave front required in order to radiate constant SPL over the listening plan Last update October 10 2014 7 V audio 1 3 DGRC The StepArray system The main characteristic of an array is its range which corresponds to the minimum and maximum distance from the column where the SPL is constant with a given tolerance The range of a column is proportional to its height An othe
11. StepArray manual Active audio CONTENTS Contents Contents StepArray tutorial for recommandation 1 Sound reinforcement in large spaces 2 Overview of the StepArray system 3 Choosing the right installation set up 4 Column positionning rules 5 NUT processor and control software 6 CAD modeling References ll StepArray technical reference 7 Installation of the columns 8 Wiring 9 Test before powering up 10 NUT control software 11 Troubleshooting 12 Hardware specifications 13 Acoustical data List of Tables List of Figures 12 14 16 16 17 19 20 21 22 23 23 24 28 35 36 V audio CONTENTS Foreword StepArray is a versatile line array system designed for speech reinforcement in large spaces lt offers excellent sound intelligibility slim design external electronics security systems compatibility and more This reference manual is intended to be a user manual for StepArray based systems as well as a complete reference with all the technical specifications and details about the StepArray system How to use this manual This reference manual is divided in two parts e The first part is a tutorial for recommandation It deals with StepArray design and principles introducing the acoustic background necessary to understand sound reinforcement in large space and how StepArray can help to achieve good intelligibility in these places e The second part is a technical
12. als 20Hz 20kHz O 1W 1dB 10kQunbalanced 20kQ2 balanced Very 95d B gt 300 Adjustable with 6 knobs on rear panel Max voltage gain 28d B THD 0 1 O 1kHz Variable speed fan Protection against overload and overheat Clip and Protect LEDs 483 x 88 x 420mm Rack 19 2U For further information see the MPA6150 owners manual 25 V audio 12 3 Columns characteristics 12 3 Columns characteristics 12 3 1 Electrical characteristics of StepArray columns Channel 1 2 3 4 5 6 SAIO 660 660 660 gt gt CSATBOP 660 6 60 600 CSA250P 6 60 6 60 6 60 110 440 4407 Psataos 660 660 660 SA250S 3 30 6 60 6 60 440 440 3307 Table 5 DC resistance of StepArray columns For details on connector pin assignement see figure 16 on page 22 in section 8 3 12 3 2 Mechanical characteristics of StepArray columns 34mm to 55mm Figure 17 StepArray column dimensions 26 V audio 12 3 Columns characteristics Dimensions Weight Cable LxWxD mm net shipping SA100P 1024 x 124 x 131 9kg 12kg SA180P 1840 x 124 x 135 17kg 21kg Table 6 Mechanical and electrical characteristics of StepArray columns More precise schematics are available on Active Audio s website in several formats http www activeaudio fr en gamme steparray catalogue et telechargements 12 3 3 Fixing brackets 121 51 71 22 N ii wz M Red is
13. ber of DSP and amplification channels is independent of the number of loudspeakers so that a dramatically reduced number of channels is achieved Ative audio Fy F2 F3 Input signal EQ F4 F5 F6 Figure 4 The DGRC principle used by StepArray columns The wave front is controlled both by the positioning and orientation of the loudspeakers and by filters F delays D and gain G of each channel The main advantages brought by the DGRC principle used in StepArray columns are e The column is vertical and can be fitted close to the wall Reduced number of electronic channels both for DSP and amplifiers For example model SA250P which is 2 5m high uses only 6 channels for 30 loudspeakers This can make a big cost difference Power is uniformly distributed to all loudspeakers This way they can all be used at their maximum capabilities enhancing overall performance and sound pressure level The number of channels does not depend on the number of loudspeakers Therefore many small full range loudspeakers can be used to obtain perfect sound quality in the treble range and reduce secondary lobes at higher frequencies 2 Overview of the StepArray system The StepArray range consists of several column models dedicated to speech diffusion and to mid power mu
14. column cable Cable length Table 3 Wiring recommendations for StepArray columns For distances exceeding the maximum cable length mentioned in table 3 please contact Active Audio e 3 channel columns need a 4 wire cable e 6 channel columns need a 7 wire cable 3 5 Subwoofers In cases where the StepArray system diffuses music the sound fidelity will be better if a subwoofer and its associated amplifier are added This option is not necessary for installations aimed at vocal diffusion since the human voice hardly has component frequencies in the bass range below 150 Hz The subwoofer signal is delivered by the NUT processor with appropriate filtering 4 Column positionning rules When choosing a StepArray setup the goals are e Ensuring proper SPL coverage e Delivering satisfying intelligibility of vocal messages Avoiding echoes and feedback effects e Giving the feeling that the sound comes from the speaker The positioning of columns should follow a few basic rules Use as few columns as possible choose the column covering as much of the listening area at once Add more columns only if necessary Beware intelligibility could be impaired if there are too many columns Columns should be placed so as to obtain the most homogeneous sound level over the audience area For complex cases it is highly recommended to use CAD software which will take into account the acoustics of the room CAD tools a
15. e The parameters of the StepArray block Check that the parameters in the are wrong StepArray block of NUT control are correct see figure 9 on page 13 The column model of the StepArray Correct the column model in the block in NUT control doesn t match the StepArray block real column model Last update October 10 2014 23 Ative audio 12 Hardware specifications 12 1 NUT processor 24 Audio data 8 symetrical analog inputs Euroblock connectors Max input voltage 8V rms 20dBU Phantom power ON OFF on each input Selectable line mic level for each input 8 symetrical analog outputs Euroblock connectors Max output voltage 8SV rms 20dBU 28bits 48kHz 192kHz General data Communication Ethernet 10 100MB USB no driver needed RS232 for remote control mains 28V DO 220VIS0Hz power supply notes Dimensions 4805 11x 251mm PRO O fine audio 12 2 MPA6150 amplifier Audio data Operating modes Power consumption Analog inputs Frequency response Input Impedance Sensitivity Signal to noise ratio Damping factor Harmonic Distortion General data Last update October 10 2014 12 2 MPA6150 amplifier 6 independent channels 3 independent channels bridged 2 x 3 channels inf out 1 2 3 in2 out 4 5 6 6 x 100 W under 822 6 x 150W under 40 3 x 300W under 842 bridged Typical 100W Max 1kW 6 symmetrical analog inputs Phoenix connectors 6 outputs on screw termin
16. e CAD tools to properly model the StepArray columns are included in CAT T Acoustic and EASE Figure 12 on the next page shows examples of a modeling results for CAT T Acoustic and EASE 16 as REFERENCES f gt t 4 40 30 p gt A N sil di a 0 SS ye 4 Ep gt a Example of RASTI modeling using software CAT T Acoustic b Balloon plot of SPL radiated in octave 1 kHz by column SA250S Simulation with EASE Figure 12 Examples of a CAD modeling results References DGRC Arrays X Meynial DGRC arrays A synthesis of geometric and electronic loudspeaker arrays AES 120th Convention Preprint 6786 Paris May 2006 C HEIL Sound Wave Guide US Patent 5 163 167 Inventor C Heil nov 10 1992 DSP directivity G W J van Beuningen E W Start Optimizing Directivity Properties of DSP Controlled Loud speaker Arrays Reproduced Sound 16 Conference Stratford UK 17 19 Nov 2000 Institute of Acoustics Last update October 10 2014 17 StepArray Technical manual Aline audio Part Il StepArray technical reference Table of Contents 7 Installation of the columns 8 Wiring 8 1 NUT processor to MPA6150 amplifier 8 2 MPAGIOU amplifier Seip 24 4644 4 4a amp Da de A EEA ERD EDS do Wiring ampliliers to columns 2 2 5 4 a eee de de sn a SO 9 Test before powering up 10 NUT control software 11 Troubleshooting 12 Hardware sp
17. ecifications LA IMITAN gt REDE ES ARA PE AS ASR ARARAS RASA SSS o MEG GA Li nda PA LESS dh DA LHES 12 3 Columns characteristics Lu 4 Ra 8 Se de AEREAS ge 13 Acoustical data PEL COMIDA eee a da RA be RNA Es a RA a EEA Loe SAMPA gi ee Ee AA EA AMA PRE ER DRDS ARES ODE 134 5AZ2J0F acoustical on kb ee eee Ew Ree oe e 13 5 RAM acoustical OM e so Loi ane sea BEES DHEA ASS eines 13 0 CA acoustical OMR LIL RNCS MINOR EAN NAN FEI Ne 13 7 5A295905 acowtical OMR gt s pas sie sue sein as Pie ses e ess List of Tables List of Figures Last update October 10 2014 20 21 21 21 22 22 23 23 24 24 29 26 28 28 29 30 31 32 33 34 35 36 19 Ative audio 7 Installation of the columns StepArray columns are mounted verticaly usually on a wall using the supplied brackets Figure 13 illustrates the steps to follow for column mounting See also figure 18 on page 27 for technical drawings of the brackets Place the 2 brackets on the wall using 8mm diameter screws Column height 5mm Ensure Laie Mount the column verticality using the supplied nut and screw Figure 13 Column mounting on a wall A It is important to ensure verticality when mounting StepArray columns 20 8 Wiring 8 1 NUT processor to MPA6150 amplifier A NUT processor can be connected to one or several StepArray columns via amplifiers see figure 14 Wh
18. en a NUT is used with several amplifiers to feed several columns with the same signal the inputs are simply daisy chained see figure 14b NUT MPA6150 NUT MPA6150 MPA6150 a Direct wiring b Daisy chain wiring Figure 14 NUT to MPA6150 wiring 8 2 MPA6150 amplifier setup MPA6150 amplifiers should be tuned with all gains to max and microswitches set for independent channels as described in figure 15 All gains a cP Peretti ret EEE STEREO IN4 BRIDGE Set all microswitches for 6 independent channels Figure 15 MPA6150 amplifier set up Last update October 10 2014 21 V audio 8 3 Wiring amplifiers to columns 8 3 Wiring amplifiers to columns Wiring amplifiers to columns is straightforward simply connect each channel of the MPA6150 amplifier to the corresponding channel of the column and provide a common ground as illustrated by figure 16 SA100P 6 channel column cabling on MPA6150 amplifier e Column output on channels 1 2 3 CH1 CH2 CH3 CH4 dh 4h 4h 4h 4b ab ah ah VP LAS LAN LA LA LAS LAN AZ Column output on channels 4 5 6 CH1 CH2 CH3 CH4 CHS CH6 CH3 CH4 CH5 CH6 GND Figure 16 MPA6150 to column wiring 9 Test before powering up Before powering up an installation it is good practice to ensure that the column cable is properly connected to the column Therefore the electrical r
19. esistance of each channel of the column must be controlled at the end of the cable connected to the amplifier side The measured electrical resistances values must correspond to the values below chema 2 Ja Ts smoor aan oan een smeo 650 660 660 RUES 22 Active audio For details on connector pin assignement see figure 16 on the facing page When measuring the electrical resistance the cable resistance must be taken into account about 1 312 for 100 meters of 1 5mm 0 70 for 100 meters of 2 5mm 10 NUT control software The NUT control software is used to tune the filtering and directivity parameters of StepArray columns it is available as free download on Active Audio s web site http www activeaudio fr en public address sound reinforcement digital signal processor nut 11 Troubleshooting Symptoms Possiblecause Possiblecause The power LED of the NUT A fuse burned Replace inside the NUT ns A A een Amplifier to column connection is Make sure columns are properly The sound is not incorrect connected as described in section 9 on homogeneous or distorted the preceding page Input signal level is too high Reduce input signal level Max signal input is 8V rms as described in 12 1 on the following page Filtering parameters are wrong Reduce the gain Mixer Block Correct the equalization There is a wiring problem Make sure the wiring is correct see 9 on the preceding pag
20. gibility ey even in reverberant spaces a 2SPL reinforcement by reverberation can be higher close to walls in this context propagation distance is the column to listener distance Last update October 10 2014 15 Aline audio 5 NUT processor and control software The NUT audio processor performs the digital signal processing needed to control the directivity of StepArray columns The NUT control software is used to tune the NUT audio processor It is available as free download on Active Audio s web site http www activeaudio fr en public address sound reinforcement digital signal processor nut The NUT processor is very flexible in its usage it gives access to a full range of functions including equalization delay compressor automixer feedback fighter presets and directivity control The directivity control block allows the user to change the radiation pattern of StepArray columns in real time This block is presented in figure 11 Figure 11 StepArray directivity control with the NUT software 6 CAD modeling There are powerful CAD software tools that can predict the acoustics of a room and accurately model the radiation of loudspeaker arrays These tools can calculate various acoustic index such as reverberation time sound pressure level STI In a loudspeaker array all loudspeakers operate in a coherent way This must be taken into account in the modeling To do so software modules which enables th
21. irectivity sound level for the voice octaves 500Hz 1kHz 2kHz on the listening plane SPL dist SA180P 15 250Hz 500Hz 10 j 1000Hz 2000Hz 4000Hz 5 _8000Hz 0 5 10 15 0 5 10 15 20 25 30 35 c Sound level by octave in the axis of the listening plane in front of the column with respect to the distance from the column Figure 22 SA180P acoustical data 8 Column is in nominal position Levels are referenced to the mean SPL on the listening area 30 V audio 13 4 SA250P acoustical data 13 4 SA250P acoustical data 100B 10dB E 10m 20m 30m 40m 50m b SA250P horizontal directivity sound level for the voice octaves 500Hz 1kHz 2kHz on the listening plane SPL dist SA250P 15 T 250Hz 500Hz 10 3 1000Hz 2000Hz 4000Hz 5 8000Hz 0 _5h 10 15 0 5 10 15 20 25 30 35 40 45 c Sound level by octave in the axis of the listening plane in front of the column with respect to the distance from the column Figure 23 SA250P acoustical data Column is in nominal position Levels are referenced to the mean SPL on the listening area Last update October 10 2014 31 V audio 13 5 SA400P acoustical data 13 5 SA400P acoustical data 10dB SA400P vertical directivity sound level for the voice octaves 500Hz 1kHz 2kHz in the vertical median plane 10dB 50B OdB 5dB 10dB 15dB 200B 10m 20m 30m 40m 50m 60m b SA400P h
22. lains the rules to follow when designing a StepArray system Column positionning is described in section 4 NUT control software serving both as a simulation and tuning software is described in section 5 CAD modeling tools are presented in section 6 1 Sound reinforcement in large spaces 1 1 General issues with public address in large spaces Speech reinforcement in large and reverberant rooms is made difficult by several causes namely reverberation ambient noise and architectural constraints Reverberation In all rooms sound transmission from a loudspeaker to a listener can be divided in two parts figure 1 Direct sound which depends on the loudspeaker to listener distance and on the loudspeaker directivity Reverberated sound which depends on the geometry of the room and the acoustical properties of the walls In large spaces church railway station the reverberation can be very important and plays a negative role on speech intelligibility Note that the energy of the reverberated sound is constant throughout the room Reverberated NY lt Figure 1 Direct sound increases speech intelligibility reverberated sound impairs it Intelligibility rule 1 Direct sound increases speech intelligibility reverberated sound impairs it Last update October 10 2014 5 V audio 1 1 General issues with public address in large spaces Ambient noise Ambiant noise reduces intelligibility For exam
23. n leads to poor intelligibility all loudspeakers contribute to the reverberation while only a few contribute to direct sound Using highly directionnal loudspeakers is an easier solution in large spaces because only few diffusers are needed In addition to improved acoustic performance and reduced cost it minimizes the aesthetical impact of the public address system Sound quality Intelligibility is not enough for good perceived sound quality Another very important aspect is that every listener has an adequate sound pressure level SPL which implies that the public address system provides an even coverage of the audience area This can be acheived with an accurate control of the loudspeaker directivity Acoustic comfort also implies a wide frequency bandwidth and low harmonic distortion a The most important goal of a public address system is to provide a strong and constant direct sound over the entire audience area and minimize the energy emitted elsewhere 1 2 Loudspeaker arrays Loudspeaker arrays are often the best solution to providing strong and constant direct sound over the audience Indeed although a distributed public address system might yield a relatively constant SPL over the audience using a large number of loudspeakers it is usually not able to provide satisfactory speech intelligibility when reverberation in the room is high In addition it usually has a rather negative impact on the visual aspect of
24. orizontal directivity sound level for the voice octaves 500Hz 1kHz Priel on the listening plane SPL dist SA400P 15 250Hz 500Hz 10 7 1000Hz 2000Hz 4000Hz 8000Hz 15 0 10 20 30 40 50 60 70 c Sound level by octave in the axis of the listening plane in front of the column with respect to the distance from the column Figure 24 SA400P acoustical data 1 Column is in nominal position Levels are referenced to the mean SPL on the listening area 32 V audio 13 6 SA180S acoustical data 13 6 SA180S acoustical data SA180S vertical directivity sound level for the voice octaves 500Hz 1kHz 2kHz in the vertical median plane odB OdB 0dB 10dB 15dB 20dB b SA180S horizontal directivity sound level for the voice octaves 500Hz 1kHz 2kHz on the listening plane SPL dist SA180S 250Hz 500Hz 1000Hz 2000Hz 4000Hz 8000Hz c Sound level by octave in the axis of the listening plane in front of the column with respect to the distance from the column Figure 25 SA180S acoustical data Column is in nominal position Levels are referenced to the mean SPL on the listening area Last update October 10 2014 33 V audio 13 7 SA250S acoustical data 13 7 SA250S acoustical data 10dB SA2505 vertical directivity sound level for the voice octaves 500Hz 1kHz 2kHz in the vertical median plane odB OdB 0dB 10dB 15dB 20dB
25. ple the loud noise produced by trains in railway stations could prevent the listener from understanding a message properly Also the noise level can change drastically over time in this case the public address system must adjust its diffusion level according to the noise level Eh intelligibility rule 2 The public address sound system should emit at least 104B above the ambient noise level Architectural constraints Loudspeakers positionning is often restricted by architectural or practical constraints Because loudspeakers are not always welcome in places where aesthetics are important they should be made discreet and as few as possible should be used Speech intelligibility in large spaces As seen above speech intelligibility depends on e Reverberation time This is a caracteristic of the room acoustics and depends on the material of the wall and the geometry of the room Direct Sound i 2 Reverberated Sound energy ratio This depends on reverberation time room volume loudspeaker to listener distance and loudspeaker directivity Signal Noise ratio This depends on the ability of the sound system to emit enough energy to cover the noise In large spaces changing the reverberation time involves changing a significant portion of the wall material and most of the time this is not possible Providing a strong signal to noise ratio is also important but it is not enough to ensure intelligibility
26. r important characteristic of an array is the spacing between loudspeakers Good rejection of secondary lobes at high frequencies is obtained with a short spacing At high frequencies geometric arrays generally use waveg uides that radiates like an isophase vertical slit Aligning several of these waveguides yields a semi continuous line source which greatly reduces undesired secondary lobes Wave front a In a geometric array loudspeakers are aligned b In an electronic array loudspeakers are aligned vertically and along the shape of the wave front to be generated the wave front is synthesized by adequate filtering by filters F de usually a J shape lays D and gain G associated to each loudspeaker Figure 3 Electronic and geometric arrays 1 3 DGRC The StepArray system The StepArray columns implement the DGRC line array principle Digital and Geometric Radiation Control which is a synthesis of geometric and electronic arrays patented by Active Audio The principle is illustrated in figure 4 on the facing page The key idea is to split the desired wave front into sections and move them back on a vertical line much like what is done in the Fresnel lenses used in optics Then electronic delays are used to compensate sound propagation delay between the sections lt was shown in DGRC Arrays that with this delay setting there is no diffraction at the edges of the saw tooth shape As a result of this principle the num
27. re presented in section 6 These maximum cable lengths correspond to a sound level loss of 3dB 14 Active audio Place the columns as close as possible to the nominal altitude see table 2 on the preceding page When placing columns at non nominal altitude use NUT control software to check that column emission will be acceptable When dealing with several columns the differences of propagation distances for columns covering the same listening area should be less than 20m so as to avoid possible echoes for certain sections of the audience See figure 10 Column 1 Column 2 U If d1 d2 lt 20m there is no echo U Listening area Listener Figure 10 Interferences between columns Also consider microphones and stage e the speaker must be placed at less than 15 m from the columns otherwise he will hear the echo of his own voice the audience must feel that the sound comes from the speaker This is achieved by fitting a column on each side of the stage so as to re centre the sound A single column can be used but in this case it has to be close to the zone to be covered Prevent the feedback effect there should never be a microphone aiming at a column this could generate a feedback problem The impact of the room acoustics on the sound level within the covered zone is relatively low 7 since the fun damental aim of the StepArray columns is to provide a strong direct sound in order to ensure high intelli
28. sic diffusion in large and or reverberant enclosed spaces The different models allow coverage of flat or tilted audience area ranging from 15m to 68m with perfect speech intelligibility and high sound quality Last update October 10 2014 9 V audio 2 1 StepArray system example StepArray columns use external electronics They are controlled by the NUT digital signal processor DSP and powered by the MPA6150 6 channel amplifier Having external electronics has the following advantages Possibility to use a single NUT processor controling several columns yielding a large cost reduction see section 2 3 on the next page Possibility to use several amplifiers for a single column in order to increase security failure of one amplifier would only affect some of the channels but the column continues to diffuse messages For example when using 2 columns and 2 amplifiers amplifier 1 can be connected to channels 1 3 5 of both columns and amplifier 2 to channels 2 4 6 of both columns Easier maintenance all electronics can be easily accessed in the technical room Electronics can be placed in a fireproof room with uninterruptible power supply UPS The operating parameters of the NUT processors are tuned with the NUT control software NUT processors feature filtering functions such as the control of directivity equalization delay and high level functions 2 1 StepArray system example Figure 5 is an example of a complete StepArray
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