Total posts : 45366
MS stereo mic’ing technique is one of my all-time favorites, because if you know how to manipulate dynamics in post, you can have a lot of sound stage image control. That’s why they often use it in film production. No other technique can offer as much control. However, generally I would not choose an MS setup for live performances, yet in a choir setup where group and mic placement are always the same, I suppose it might be OK once you’ve derived the best you can get from it … then leave it alone … if you have to, screw a plastic key lock plate over the channel to keep the knobbits from messing with it 😉
Phase cancellation works basically the same in AF as it does in RF, albeit sound travels orders of magnitude slower. Any mic picking up at least part of the same sound as another one placed some distance away means they are very likely out of phase with one another to more or less degrees, which will invariably cause some cancellation in one band and noise in another. If this occurs, the mix gets muddy, you often end up fighting yourself to clean it up.
The only semi-effective help I know is to fiddle with parametric EQ in the mixer channels to try and dovetail, i.e., sweep to find offending band, then boost/cut adjacent freqs from one channel to the other. That might help prevent phase cancellation, but it also means some sound will be subtracted from one, added to another. If it doesn’t sound right, try reversing the settings … because overtones may differ from one to another.