Another variation of using different EQ settings on the left & right channels is to convert the Left & right into MS and then you can EQ the Side (difference between left and right) differently to the M (left and right added together) then decode the MS back to left and right. This is a trick mastering engineers use to EQ the stereo part of the signal but leave the mono components alone.
The Flux Epure EQ plug-in, for example, has this feature built in. By hitting the Setup button under the Master Gain control you can set up the MS encoding, decoding and routing through the plug-in.
Then Group 1 will process the M channel,
and Group 2 will process the S channel.
Acon Digitial Equalize Plug-in
Another EQ plug-in that has built in MS processing is the new EQ plug-in from Acon Digitial. You can see my show and tell review where I cover this and this month you can take advantage of the exclusive deal we are offering on Equalize and buy it for just £39 which is a 39% discount on the normal price.
Don’t have these plug-ins?
It is also possible to the MS encode/decode with just aux tracks. The maths for MS encoding are simple L+R=M, L-R=S and decoding L=M+S and R=M-S.
So to encode take the L & R and mono them to create L+R - the M channel. On another aux track take the same L & R and mono them but insert a Trim plug-in with a phase reverse on one side. This will provide the S channel, which is L-R. Now route the L+R into one side of an EQ plug-in and the L-R to the other side. Now to get back to left and right, take the output of the plug-in and route the M channel to a mono aux track so it is panned centre across a stereo mix and route the S channel through a stereo aux track with a phase reverse in one side and pan hard left & right to the same stereo mix as the mono channel. OK it isn’t simple but once you have done it once, make a template session of it and you can quickly bring it in to any session you need it on.
Julian Rodgers has created this session that he uses to help students understand how Mid/Side works.
You can show the hidden tracks and follow the signal flow through the busses. The comments in the mixer should help. Here is a version of the session in .ptf format for Pro Tools users running v7 to v9