Mid Side (M-S) is a unique stereo recording technique that allows complete control over the stereo image during mix-down.
Technique
M-S technique consists of a “mid” center position microphone and on “side” bidirectional microphone. The mid microphone is typically pointed directly at the sound source from a desired distance and the “side” microphone is place just above or below the center microphone making it a coincident technique. The technique requires a decoder. Some manufactures build specific decoders, but decoding or a “Matrix” can be set up on an analog console or digital workstation. The center microphone, which can be any type of polar pattern (Cardioid, Hyper-Cardioid, Bidirectional etc.) is panned to the center and the “side” microphone is split into two identical signals. One of these signals is polarity inverted and they are panned left and right respectively. After the “matrix” is put together a mix of the “mid” and “side” microphones can be used to gain desired stereo results. More “sides” = more phase inconsistencies “wider stereo image.” less sides = less phase inconsistencies “more narrow stereo image.” The unique feature of Mid Side technique is its ability to be mono compatible due to the phase reversed “sides” being canceled out when summed to mono, leaving only the “mid” microphone.