ici il y a plus d'explication :
http://www.akaipro.com/productsVSTPlugins.html
The Akai Professional Quad Comp VST plug-in is a multi-band compressor/expander that can be used for mastering purposes.
While it is possible to use an ordinary compressor for tightening up and adding punch to a stereo mix, it is very common that low frequencies can cause 'pumping' effects on the overall signal. However, by splitting the signal into four different frequency bands, each frequency region can be separately processed. This is achieved on the Quad Comp using a series of crossover filters. These filters are constructed as linear phase FIR filters in order to produce a signal path which is perfectly free of phase errors. Crossover frequencies can be set for the four bands from 50Hz to 12.5kHz and the slope is selectable from 6 to 24dB/octave.
Each band has controls for THRESHOLD, RATIO, ATTACK and RELEASE and as these are adjusted, the compression curve is shown graphically. The GAIN control allows you to compensate for level changes that may occur.
Input and output levels for each band are shown as is the amount of gain reduction.
The panel can be switched between the multi-band compressor and the multi-band expander.
The Quad Comp VST Plug-in provides multi-band compression/expansion without any phase distortion or cancellation, thanks to its unique linear phase FIR crossover filters.
![:lol:](https://www.homecinema-fr.com/forum/images/smilies/icon_lol.gif)