Sound Reasoning: Recording Stereo Sound (page 3)
M/S Miking Technique
M/S, or middle/side miking, uses one cardioid mike facing directly forward at the middle of the sound source, and one bi-directional mike just above or below it to pick up side and indirect sound (see figure 2c). A bi-directional mike picks up sound most strongly from two sides, but unlike a stereo mike, a bi-directional mike outputs only a single signal. The outputs of both the cardioid and the bi-directional mikes are sent to a special matrixing electronic circuit (basically a transformer and supporting circuit) which derives the left and right stereo signals.
Several manufacturers sell M/S miking systems which include the matrixing box. It's usually not necessary to use an audio mixer with M/S miking systems, since the electronics act as their own mixer, unless you wish to include other sound sources in your audio tracks.
Among all these systems we've discussed, M/S miking can produce the best possible stereo sound when properly used. M/S miking systems generally incorporate adjustments between the center and side signals, allowing flexibility in the amount of separation you desire. Most stereo zoom mikes (which zoom in on sound much the same way your lens zooms in on pictures) use this adjustment for their effect. In fact, most built-in stereo camcorder mikes use the M/S miking system in either a fixed or zoom configuration.
To Sum Up
By now, you should have a good basic idea of how to record quality stereo audio. You should know if your equipment can record stereo, or what you'll need if you plan to buy new gear. You should understand the connections you'll need to make, and see the advantages of using a mixer when recording. You should understand the advantages and disadvantages of recording stereo using the external stereo mike, the different X-Y miking placements and M/S miking.
All of these techniques will provide you with the basic tools you need to record much better sound tracks than simple mono setups will allow, and to excite your audiences with the full-bodied quality of stereo sound. So let's dust off those mikes and go make some stereophonic sound.
