Stereo linking of compressors is something most of us do without really examining why. We understand that the stereo image can be affected by loud, off centre sounds unless compressors are linked but how often does that happen and is it always a bad thing? In this article Julian Rodgers asks why and whether we should link stereo compressors?
Watch the video below, an extract from Chris Lord-Alge Mixing Daughtry on PureMix. In his typically direct way, CLA explains why he never links stereo compressors. The orthodox method is to link pairs of compressors on stereo material. Stereo reproduction relies on level differences between the channels and if a loud sound, panned off centre causes one side of a stereo compressor to attenuate without a corresponding attenuation in the other channel, the stereo image will shift.
What Is So Bad About Compressors Causing Stereo Shifts?
Like so many things, it depends. In the example above CLA is compressing drums in a rock mix. A little movement adds excitement and modern rock music isn’t a naturalistic style of recording in the same way as a classical or a jazz recording represents capturing the sound of a performance in a room with accuracy or authenticity.
Taking the example of classical recording, while it’s unlikely that a significant amount of compression would be used recording an orchestra, if it were to be you might quickly find the orchestra audibly shifting around. The cellos, basses, timps and bass drum are all traditionally placed to the right, with the basses to the far right. If a hypothetical rock mixer were to apply typical amounts of unlinked compression to a recording of this orchestra playing something like Holst’s “Mars” the first violins would be moving over towards the violas when the basses chugged!
CLA spoke about how linked compressors make things “sound more mono”. That’s interesting. He’s not talking about things being more “stereo” because of the shifting of the stereo image when compressors are unlinked, it’s a little more complicated than that. Stereo linking can make things sound less stereo but it depends what is causing the perception of “stereo-ness”. In this excellent video from FabFilter Dan Worrall explains stereo linking.
There is a lot in this video but pay particular attention to the difference between the effect stereo linking has on the coincident pair of overheads compared to the spaced pair of room mics. Because the stereo cue our brains are using to infer the position of the elements of the kit in the coincident pair is based on level and the stereo cues presented by a spaced pair are based on difference in in time of arrival there is a difference in the effect the changes in level will have on the stereo image.
Returning to our earlier example of a rock engineer mixing an orchestra playing Holst, as orchestral recordings frequently use spaced arrays to capture the performance, maybe our assumptions about the effect unlinked compression would have on the recording aren’t as cut and dried as we assumed. I still wouldn’t slam an orchestral recording through an 1176 but that’s not really the point.
If you’ve always left your stereo compressors linked, try unlinking them. There are rules but as we all know, rules are to be broken!