FabFilter User Forum
Is the Pro-Q 3 MS mode working correct?
I wanted to use the Pro-Q3 as a MidSide decoder. Input is a stereo signal with on the left channel the Mid and on the right the Side signal. When switching on the MS mode the Mid stays on the left. When turning the MS pan ring to full Mid the signal goes equally to both L and Right. The Side however is then at INF level. As I know from post production the Mid signal should stay at the center at anytime. And the Side is put + to the Left and - to the Right.
Is this workflow correct?
Danny van Spreuwel — May 1, 2019
I don't think this is possible.
You'd always feed it a usual L/R stereo signal and ProQ is internally able to encode it M/S, apply its filters to it as well as change the ratio and decodes it to a L/R signal eventually.
Thing is, Pro-Q3 expects a stereo L/R signal, it does it's MS encoding within the plugin itself, so input and output are always identical. So you put M/S in, you get M/S out, same for L/R.
I'd just use a M/S matrix (there are free ones available) before Pro-Q3, to get the result you want.