7 Replies Latest reply: Jul 16, 2009 1:48 PM by SteveG(AudioMasters) RSS

    Multiband Compressor is EQing waveforms while Bypassed

    Eric S 1 Community Member

      I think I've read something about this in the past.  It was about the "sound" of the Multiband Compressor.  I didn't pay much attention to it until I ran across this phenomenon myself these past few days.  It seems the Multiband Compressor does indeed change the EQ of a waveform when bypassing every single band and the limiter.  I was hearing this issue when I was attempting to use it for a current project - basically I was hearing some mid-frequency attenuation.  So I thought I'd test it with some generated Pink Noise and look at the different traces in the Frequency Analysis window.  I've attached the picture of the two traces.

      10 seconds of Pink Noise was generated.  I did a Frequency Analysis of the Pink Noise - the analysis window FFT Size is set to 32768 Blackman-Harris for each scan.  I saved the Pink Noise as the Green Trace.

      Then I opened the Multiband compressor.  I engaged the Bypass button for each band and for the Limiter.  For each band I also set the Threshold to 0, the Gain to 0 and the Ratio to 1.0 to 1.  The Brickwall Limiter was disengaged (unchecked).  The Limiter settings had a Threshold of 0 and a Margin of 0.  The Output Gain was also set to 0.

      I applied the Multiband Compressor to the entire Pink Noise waveform and then did another Frequency Scan.  The resulting trace is in Red.

      As you can see, there is a serious dip at 1540Hz and the width is fairly wide.

      To me this makes the Multiband Compressor completely unusable and unreliable.  One would think that the Compressor would be neutral until something on it is engaged.  This is obviously not the case at all.

      Has this issue been discussed before and I've just missed it or has no one else really caught this issue?  Is anyone else able to replicate this?