Quantum user manual333
Contents
1. inPUT Gain The Bypass toggle switch gives the user the choice to bypass entirely the plugin Its an easy way to hear the difference between processed and unprocessed audio The Low cut provides the ability to cut ofl undesirable frequencies below 30Hz with a very agressive slope of 30dB Octave This proves to be handy to clear out the mix of sub frequencies that eat up un necessary energy in the mix It is active by default Magnitude dB Frequency Hz Figure 3 Fixed 30Hz Low cut Figure 4 The High cut provides the ability to cut off undesirable frequencies above 18kHz with a very agressive slope It is active by default Quantum Matering User Manual 7 2 3 Band functions Magnitude dB i o god b gd H g ui B B WW SN M RR ecu oc un Q n O u Frequency Hz Figure 5 Fixed 18kHz High Cut As seen on this logarithmic frequency scale the response drops dra matically at 18kHz when the High Cut is active A true razor blade cut With the Input gain the user can choose the master gain of the plugin It is set by default at OdB but you may use it to reduce the input down to oo if some eq ing makes the signal peak to 0 dBFS If the input is not hot enough the Input gain control enables you to boost it up to 12 dB With the Mid side button the user can select either Left Right operation default mode red LED is off or Mid Side operation red LED is on2. Quantum Matering User Manual 11 3 Digital Signal Processing 3 1 Filter types 3 2 Filtering There are 5 different filter types implemented in Quantum Mastering EQ bell filter high shelving low shelving high cut and low cut As discussed in the Using Quantum LPEQ section what makes this plugin unique is that the bell filter is actually a square shaped filter that can be adjusted through the Precision parameter to get either a bell shape or a shelving shape The core of Quantum Mastering EQ is built around digital filters called FIR for finite impulse response As discussed briefly in the About section of the user manual the other type of digital filter is IIR for infinite impulse response FIR filters are finite because they do not have feedback meaning if you feed an impulse to filter the output will become zero in finite time after the impulse has made its way through the filter Figure 7 FIR filter graphical representation IIRs on the other hand have non finite impulse response meaning if you feed an impulse to the filter the output does not necessar ily become zero after finite a finite time duration because there is feedback Digital filters are spoken of in terms of taps which are the coefficients in the filter equation Because of the feedback present in IIR filters they are much more efficient and they require fewer taps to provide the same frequency response as FIR filters From a computing poi
3. What it does basically is transforming the audio signal for example the song on which youre doing mastering from the time domain to the frequency domain This way instead of doing a con volution between the filter and the audio signal in time domain we Quantum Matering User Manual 13 3 4 Algorithm 4 Conclusion apply the to both signals after which we can process them in frequency domain And as we mentioned earlier the convolution be comes a simple multiplication which is much less costly for the CPU As you can see in the following table for a small number of taps processing audio in the time domain is not that demanding but it grows exponentially fast when you want a more precise FIR filter with more taps As we have experienced during the development phase of this plugin using FFT becomes inevitable at some point to have the EQ running smoothly without lag or glitches Direct Convolution 176 16 2560 1024 5888 4096 13 312 16 384 29 696 65 536 311 296 4 194 304 Figure 9 Convolution FFT vs direct convolution To finish here s an overview of the algorithm used in Quantum Algo rithm LPEQ In conclusion we hope you will have fun using Quantum Mastering LPEQ and that it will become a helpful studio tool for you For more information about mastering and sound science please visit http www quantum music ca Programming team e Simon Bizier e Alexandre Brunelle e Guillaume P
4. s spread in octaves musically separated each side of the selected fre quency So the filter can precisely influence a frequency range of 4 octaves half of a piano range down to a surgical 1 10th of an octave For example a BW of 2 at 440Hz means you will eq one octave above and one octave below thus from 220Hz to 880kHz At maximum Precision and BW 0 1 this would affect only frequencies between 400 2 and 484Hz just a iota more than two semitones You can see Figure 6 for relationship between frequency and notes The Precision control changes the quantity of coefficient used for calculating the filter for each EQ band It is set to maximum precision by default It ranges between 0 00 and 1 0 where 1 is max precision yielding razor sharp transitions at cutoff frequencies and with P set to 0 0 it is actually smoothing out the edges to make it sound more like a traditional EQ Now you may think that this 28 quite subtle to hear and you would be totally right but this is what mastering is all about subtlety You may have to play with this parameter for a while before you actually feel it and know how to use it properly but in the end it does make a difference in the sound Be careful at very low BW lowering P will also reduce the gain of the band s effective filter For narrow sound correction BW below 0 8 P should always be set at higher values unless you really want smooth transition edges The VUMeter d
5. Hbert e Bouchra Laabissi Quantum Music e Christopher Dion Quantum Matering User Manual 14 Filter Processing Algorithm Basic Diagram GUI Get control parameter changes from host INPUT FILTER PCM Data at given sample rate Desired spectral impulse Response CD 44100 samples second Fourier transform FFT Obtaining 8192 frequency amplitude Coefficients Calculation of the filter s Impulse Response with sin x x function Encode Mid Side Mid Side Encoding NO Frequency coefficients Multiplication Input x Filter Inverse FFT Back to Time Domain Decode Mid Side Update GUI information YES Mid Side Encoding Generate Output Signal CD 44100 samples s or Higher Sample rates Detect Peak amp Generate VU information
6. If you don t know what is mid side operation just try it it s cool What does it do With a simple trick we create a channel matrix that isolate the mono in phase part of the mix and the stereo out of phase We process this matrix the same way we process left right channels and then decode the matrix to regenerate true left right stereo image If you wish to work in MS and Stereo modes at the same time use the Link switch The Link switch yellow LED on locks an EQ band of both channels together so you can edit them at the same time providing stereo eqing This will have the exact same effect in Stereo and MS modes because mid side stereo left right Y Channel i TrueStereo With Link active if you use one band s knob or on off switch the same parameter on the same band 1 to 4 of the other channel will act as a slave The value of both parameters will be exactly the same until you deactivate Link Now for the controls that will actually make a difference in the sound Quantum Matering User Manual 8 2 Z O N For a starter if you are using a mastering plugin you should already be aware of what you can do with a Frequency knob If not you should quit the music business right away Another way of adjusting the frequency is to click on the value and enter the desired value with the keyboard The On Off switch turns on or off the EQ band Illuminated green LEDs indicate
7. att re ce d Mo NEC oe Se We ee e Ru ee G 14 4 Conclusion 14 1 About Quantum LPEQ Quantum LPEQ was designed as part of 4th year undergraduate project at Ecole Polytechnique de Montral in collaboration with Christo pher Dion from Quantum Music Our challenge in designing the Quantum Mastering LPEQ was to provide a parametric linear phase EQ for VST 2 0 with transparent sound and intuitive interface And best of all free of charge 1 1 Features Audio Sample rates 44 1 kHz 48 kHz 88 2 kHz 96 kHz Resolution 16 24 32 bits Range 20Hz 20kHz Windows 32 bit support Left Right or Mid Side operation V U meter Peak detection 6dB gain on 8 mono or 4 stereo channels Fixed 30Hz Low Cut and 18kHz High Cut Interface Solo buttons for individual channels Separate Gain knobs for individual channels and one input gain control Peak metering with VU amp peak indicator Enter values directly with the keyboard Why choose Quantum LPEQ True Linear phase processing e Innovative Bandwidth amp Precision controls Quantum Matering User Manual 3 1 2 Linear phase e Cost e Ressources available at quantum music ca With its parametric design each band can be adjusted in terms of frequency bandwidth and Q factor to give as much control possible to shape the sound spectrum For the untrained ear a non linear phase EQ which is pretty much the standard way to design EQs doesn t sound much different
8. from a linear phase one However for experienced studio engineers who crave for sound purity and don t want any coloration or for hobbyists who want the most precise equalization linear phase EQs provide a more subtle control Where minimum phase or analog EQ s add frequency smearing to the sound linear phase EQ s keep a constant timing of all frequencies which is great for making a frequency band louder or quieter without changing other aspects of its relationship with the music around it To put it into numbers a first order filter minimum phase EQ mean ing analog hardware or digital IIR filters with 6dB octave slope adds subtracts 90 degrees of phase shift over a two octaves region around the center frequency for each 6dB of boost cut For steeper slopes the filter order goes up and so does the phase shift up to a point where it goes beyond 360 degrees and really becomes a delay but only on a portion of the frequency spectrum And because the brain is particularly sensitive to this it actually uses the phase differ ence in audio signals to create the 3D image of sound messing with phase means messing with the spacial perception of music Now this doesn t mean this sounds bad it may even be something you look for in the mix that s what adding reverb does It simply means that if you already have a good mix you may want to keep it as true to the original as possible while performing some corrections W
9. that the EQ band is ON All bands are turned ON by default Now you are smart and you know what a Gain knob is for That s it it allows you to adjust the gain of each EQ band between 6 dB and 6 dB It is worth knowing that this setting is independant from the master input gain described in the previous section But you might ask yourself Why just 6dB Other EQs go to 12 15 or even 30 dB of gain attenuation Well the simple answer is f you need more than 7dB of gain attenuation at mastering immediately send the track back to mix there is a problem Filter type Above each band s On Off switch the Filter type drop down menu gives the user the choice between Bell Low Cut and High Cut filters Bell is the default setting for all 8 mono bands Now where are the shelving filters you might ask yourself Now that iswhere Quantum Mastering LPEQ is different and interesting from other traditional plugins The shelving is actually integrated in the bell and you can set it with the Bandwidth and Precision controls The Quantum Matering LPEQ is special because it uses a special method of filtering the audio signal relying on bandwidth and preci sion parameters as opposed to traditional analog and analog mod eled EQs that use a Q parameter Quantum Matering User Manual 9 The Bandwidth knob provides the ability to adjust the bandwidth for each EQ band between 0 1 and 4 The numbers reflect the equaliser
10. QUANTUM MASTERING LPEQ LINEAR PHASE PARAMETRIC EQUALIZER USER MANUAL BAN BAN m REUS Bell e HIGH CUT 6 Lad 0 b 6 w 2 ex x 98 S E E 1001 Hz 1001 Hz 1001 Hz 1001 Hz 0 0 dB 1001 Hz 1001 Hz 1001 Hz 1001 Hz BW BW BW BW BW BW BW BW 1 00 1 00 1 00 1 00 1 00 1 00 e Q e e K KE 1 00 1 00 1 00 1 00 1 00 1 00 1 00 1 00 emm INPUT GAIN 00009 8900 0 0 dB 0 0 dB 0 0 dB 0 0 dB 0 dB Quantum music ca 2013 Quantum Matering LPEQ User Manual Contents Quantum Music ca Version 1 0 2013 Thank you for downloading Quantum Matering LPEQ Keep in mind that this is a free plugin it doesn t come with any support or warranty Please read this guide carefully before using the software so you can enjoy the full Quantum experience 1 About Quantum LPEQ 3 3 1 2 phase ee eee oS 4 2 Using Quantum Matering LPEQ 5 2 1 Interface overview 5 22 Axeneral uote eA ARA GA KA S S 7 2 HB AMC UNC ONS St wed eS Os wee ie tt adi a ee 8 3 Digital Signal Processing 12 Salt JOR ay DCS Z 2 2 Q UY d ee dde Resp RUM UN WI EUR SS Wo es 12 2 Q SD b S b ip SS ee WQ ZQ 12 Duo AOODSVODUDIOB s jc om Oe dab Xu Sr Q tee de S op S Q Ae dd 13 Dub a A porn Dra ZZ X X ae Scot eh es
11. hen applying equalization using a well designed EQ the frequency response should look similar in terms of magnitude no matter if the EQ has linear phase or not As you can see on Figures 1 and 2 both filters have the same cutoff frequency of 10 8kHz blue line though with a slightly different response in the cutoff region which is keeping the phase intact all across the audio spectrum As you can see on Figures 1 and 2 green line the phase response in the passband region is linear for the FIR and nonlinear for the IIR Whether this is an advantage from an audio point of view there have been lenghty discussions about this but from a purely mathematical point of view there s no contest that linear phase EQs provide a cleaner signal Quantum Matering LPEQ User Manual 4 Magnitude dB and Phase Responses I Magnitude dB Phase radians 52 3394 a 07 8 Me 0 0 5 0 4 0 5 0 6 Normalized Frequency rad sample Figure 1 FIR filter magnitude and phase response 100 coefficients Hamming Window Magnitude dB and Phase Responses Magnitude dB Phase radians 0 4 05 0 6 Normalized Frequency rad sample Figure 2 IIR filter magnitude and phase response 100 coefficients Butterworth 2 Using Quantum Matering LPEQ In this section we are going to introduce the interface and the basic and advanced functions a
12. isplay shows a graphic representation of the audio level for each channel The red LEDs on top indicate when clipping occurs audio level over 04 If clipping do occur you should bring down the input gain by a few dBs and left click on the LEDs to reset them Quantum Matering User Manual 10 Hote MIDI Frequenc name number in Ca 108 B7 107 3728 3 Soon D 3322 4 5136 p 2960 0 sags 2637 0 106 195 104 193 F 102 igi 2459 0 349 3 E gg 100 2217 9 2093 0 ze EE 1864 7 B6 95 1760 0 e 94 gs 1661 2 568 0 92 Q 1480 0 1396 9 Bc 90 56 1244 5 n F Dn 1174 7 87 me 1108 7 1946 5 zi 85 932 33 saa a BS B3 880 00 ac 82 gi 930 61 783 99 a 80 sq 39 99 46 78 522 25 ES T 587 33 S 75 a 594 37 a5 fe 73 55 466 16 pra Bd 7l 440 0 23 70 415 30 592 00 um BB gn 309 99 449 23 E 66 311 13 2212 E4 54 233 08 oes B3 a 220 00 58 zs x eas 196 00 ae 56 OO 194 61 ES 54 os 164 81 155 56 146 83 s 51 27 138 59 199 81 s 49 116 54 1121 Be 47 110 00 p 46 ac 103 83 agg 52 44 43 92 499 307 Er 42 77 762 5 40 09 296 ang d 37 56 58 270 ohio Bi 32 55 000 xi 34 33 51 915 999 ei 32 51 46 249 654 E 30 55 38 881 Ue El z 34 648 45 203 Di 25 54 30 868 29 155 2 500 2 22 Figure 6 Notes and Frequency relationship with which you can re fer to adjust the bandwidth parameter in octaves or fractions of an octave
13. nt Quantum Matering User Manual 12 3 9 Convolution OUT Figure 8 IIR filter graphical representation of view IIR filters require less operations from the CPU and for this reason they are used quite a bit in audio notably for EQs However as you have read earlier this particular EQ is based on FIR filters which are less efficient than IIR filters Why you might ask FIR filters by definition provide linear phase which as discussed earlier is one of the main features of Quantum Mastering EQ IIR filters have non linear phase so they had to be dismissed for our use Having said that FIR filters are not efficient how did we manage to program a plugin that runs smoothly First let s start by explaining the problem with FIR filters As we said to get an acceptable filter response an important number of taps is required with FIR filters The more precise the filter the more taps required At the same time the lower we get in terms of frequency the more taps required So as you can understand obtaining a precise filter for something like 100Hz requires a lot of taps Applying a filter to a signal requires a multiplication in the frequency domain In the time domain which is how audio is heard by the human ear this multiplication becomes a convolution which is a demanding mathematical operation from a processing point of view One way to solve this problem is to use the FF T Fast Fourier trans form
14. vailable to the user We will also explain how to use Quantum Mastering EQ efficiently with an example of a mastering workflow 2 1 Interface overview The first noticeable thing when opening Quantum Mastering EQ is that the whole interface is divided into two symmetrical parts For each channel the Gain knob enables you to trim the balance between Left and Right channels or Mid and Side if operating in MS Mode Quantum Matering User Manual 5 The Solo button enables you to work exclusively on one channel at a time yellow LED turned on a critical feature in MS mode Be careful Do NOT leave this switch ON when bouncing or rendering your tracks it will be printed as is The left part is used either for adjusting the Left channel when in stereo mode or for adjusting the Mid channel when in Mid Side mode red LED turned on LEFT MID x LAL 20 Hz 20 Hz KAK 0 0500 0 0500 0 0500 6 0 dB The right part is used either for adjusting the Right channel when in stereo mode or for adjusting the Side channel when in Mid Side mode 20 Hz 20 Hz 20 Hz 20 Hz Pw we 0 0500 0 0500 0 0500 0 0500 070700 0 0500 0 0500 0 0500 Quantum Matering User Manual 6 2 2 General functions Here we will describe the plugin controls that are not band specific meaning they will affect the overall behaviour of the plugin on both channels without regards to the band settings HIGH cuT
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