Pyramix X - Page 222

Mixer : Mixer Components
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M&S Stereo Strips
What is M&S?
M&S stands for Middle and Side. M&S is a microphone technique which outputs Sum and Difference signals
instead of Left and Right (also known as LR, AB or XY). These Sum and Difference signals are often known as M&S
although this nomenclature is often a source of confusion...
Sum and Difference signals can be created from a conventional Left, Right source. For example, by using the
Pyramix MS Encoder plug-in.(Please see: MS Encoder on page 353).
Decoding M&S
A Sum and Difference or M&S decoder reconstitutes Left and Right by adding the Difference (S) signal to the
Sum (M) signal to produce Left and adding the phase-reversed Difference (S) signal to the Sum (M) signal to
produce Right. This is often represented as:
L = M + S and R = M - S
Benefit of M&S
In mixing as opposed to recording, the main practical benefit of manipulating a signal in the Sum and Difference
domain is true control over the width of the image. Pyramix can handle these signals directly thanks to the provi-
sion of M&S Stereo strips.
The new General Mixing Bus decodes MS directly and without any additional user interface. Users can feed An
MS strip can be fed with Middle and Side information as before and the Panner will decode the Left and Right
information and feed it directly to the connected Buses.
If you wish to route the raw M & S signals, switch the Bus connection to use the Channel Router instead of the
Panner.
Width Control
The Middle and Side Mixing controls which existed in the old-style busing connection are absent temporarily. So,
when using the new General Mixing Buses, users will need to change the balance between the Middle and Side
levels by using Clip Gains & Clip Envelopes.
The direct M&S mixing functionality will return in a subsequent release of the Pyramix software.
Phase Button in an M&S Strip
The Phase of both the Sum and Difference channels can be reversed. The single Ø button has four possible states:
Black: No phase inversion
White: Sum (M) channel inverted
Red: Difference (S) channel inverted
Blue: Both channels inverted
Inverting either Sum or Difference results in the image being reversed left to right.
Note: If the Input meters consistently show S higher than M then either the image is very wide
and unlikely to be compatible for a mono listener or the M and S inputs have become reversed at
some point. Regrettably, this is extremely common when dealing with location recordings in film
and TV.