What’s The Advantage?
One of the biggest advantages of MS recording is the flexibility it provides. Since the stereo imaging is directly dependent on the amount of signal coming to the side channels, raising or lowering the ratio of Mid to Side channels will create a wider or narrower stereo field.
The result is that you can change the sound of your stereo recording after it’s already been recorded, something that would be impossible using the traditional XY microphone recording arrangement.
Try some experimenting with this—listen to just the Mid channel, and you’ll hear a direct, monophonic signal. Now lower the level of the Mid channel while raising the two Side channels.
As the Side signals increase and the Mid decreases, you’ll notice the stereo image gets wider, while the center moves further away. (Removing the Mid channel completely results in a signal that’s mostly ambient room sound, with very little directionality – useful for effect, but not much else.) By starting with the direct Mid sound and mixing in the Side channels, you can create just the right stereo imaging for the track.
Another great benefit of MS miking is that it provides true mono compatibility. Since the two Side channels cancel each other out when you switch the mix to mono, only the center Mid channel remains, giving you a perfect monaural signal.
And since the Side channels also contain much of the room ambience, collapsing the mix to mono eliminates that sound, resulting in a more direct mix with increased clarity. Even though most XY recording is mono compatible, the potential for phase cancellation is greater than with MS recording. This is one reason the MS microphone technique has always been popular in the broadcast world.
Other Variations
While most MS recording is done with a cardioid mic for the Mid channel, varying the Mid mic can create some interesting effects. Try an omni mic pattern on the Mid channel for dramatically increased spaciousness and an extended low frequency response.
Experimenting with different combinations of mics can also make a difference. For the most part, both mics should be fairly similar in sound. This is particularly true when the sound source is large, like a piano or choir, because the channels are sharing panning information; otherwise the tone quality will vary across the stereo field.
For smaller sources with a narrower stereo field, like an acoustic guitar, matching the mics becomes less critical. With smaller sources, it’s easier to experiment with different, mismatched mics. For example, try a brighter sounding side mic to color the stereo image and make it more spacious.
As you can see, there’s a lot more to the MS microphone technique than meets the ear, so give it a try. Even if the technical theory behind it is a bit confusing, in practice you’ll find it to be an incredibly useful method to attain ultimate control of the stereo field in your recordings.
Daniel Keller is a musician, engineer and producer. Since 2002 he has been president and CEO of Get It In Writing, a public relations and marketing firm focused on audio and multimedia professionals and their toys. Despite being immersed in professional audio his entire adult life, he still refuses to grow up. This article is courtesy of Universal Audio.
