Get Maximum Control Over your Stereo Image

When most people think of stereo recording, the first thing that comes to mind is a matched pair of microphones, arranged in a XY pattern. It makes sense, of course, since that's the closest way to replicate a real pair of human ears.But while XY microphone recording is the most obvious method, it's not the only game in town. The Mid/Side (M/S) recording technique is more complex, but it offers dramatic advantages over standard miking. If you've never heard of M/S recording, or you've been afraid to try it, you're missing out on a powerful weapon in your recording arsenal.

History

Mid/Side microphone recording is hardly a new concept. It was devised by EMI engineer Alan Blumlein, an early pioneer of stereophonic and surround sound. Blumlein patented the technique in 1933 and used it on some of the earliest stereophonic recordings.

The M/S microphone recording technique is used extensively in broadcast, largely because properly recorded M/S tracks are always mono-compatible. M/S is also a popular technique for studio recording, and its convenience and flexibility make it a good choice for live recording as well.

Why Mid/Side?

The main weakness of the XY microphone technique is the fact that you're stuck with what you've recorded — as well as its stereo image. And in some cases, collapsing those tracks to mono can result in some phase cancellation.

The M/S technique gives you more control over the width of the stereo spread than other microphone recording techniques, and allows you to make adjustments at any time after the recording is finished.

What You Need

While XY recording requires a matched pair of microphones to create a consistent image, M/S recording often uses two completely different mics, or uses similar microphones set to different pickup patterns.

The "Mid" microphone is set up facing the center of the sound source. Typically, this mic would be a cardioid or hypercardioid pattern (although some variations of the technique use an omni or figure-8 pattern). The "Side" mic must be a figure-8 pattern. This mic is aimed 90 degrees off-axis from the sound source. 

Both mic capsules should be placed as closely as possible, typically one above the other.