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162 Chapter 12 Helper
If you chose to use the Direction Mixer simply to spread the stereo base, please keep in
mind that as the Basis values increase beyond 1, monaural compatibility decreases
accordingly. Once you process a stereo signal with an extreme setting of 2, when you
play back the track in mono, the signal will be cancelled out completely—after all, L-R
plus R-L doesn’t leave you with much.
What is MS?
Relegated to obscurity for a good long while, MS stereo (middle-side as opposed to
left-right) has recently enjoyed a renaissance of sorts. To explain; two microphones are
stacked on a stand or suspended from the ceiling so that they are positioned as closely
together as possible. One of the two is a cardioid (or omnidirectional) mic which faces
the sound source that you want to record directly—in straight alignment. The other is a
bidirectional mic, the sensitive axes of which point to the left and right at 90˚ angles.
The cardioid mic delivers the middle signal, the bidirectional mic the side signal. Simply
record the middle signal to the left side of a stereo track and the side signal to the
right. This configuration enables the Direction Mixer to easily decode MS recordings.
The advantage that MS recordings have over XY recordings (two cardioid microphones
aligned so that they are directed to a point halfway to the left and right of the sound
source) is that the stereo middle is actually located on the on-axis (main recording
direction) of the cardioid mic. This means that slight fluctuations in frequency response
that occur off the on-axis—as is the case with every microphone—are less
troublesome.
In principle, MS and LR signals are equivalent and can be converted at any time. When
“-” signifies a phase inversion, then the following applies:
M = L+R
S = L−R
In addition, L can also be derived from the sum of and R from the difference between
M and S. Here’s some interesting trivia for you: Radio (FM) broadcasts feature M and S
stereo. The MS signal is actually converted to a signal suitable for the left and right
speakers by the receiver.