Audio Developments AD146 - Manual (Page 34)

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Blumlein's microphone techniques have advantages over all others (X-Y and A-B)
such that it is worthwhile using M-S microphones even when mixing is to be done ithe
L-R domain. For example, the M-microphone will be placed in the optimum position
for a mono image, whereas mixing to mono the signals from an X-Y stereo pair
introduces phase anomalies.
When using M-S microphones we suggest, for convenience, that M-
microphones are inserted in odd-numbered channels, and the corresponding S-
microphones are inserted in the next channels above.
Many are the tricks one can perform in the M-S domain, but the only one considered
here is the possibility of changing the width of a L-R stereo signal. Should readers
wish to investigate further M-S techniques, they are invited to request a copy of
the M-S Handbook written for our PORT-A-FLEX units AD066-11,
M-S stereo
microphone amplifier and AD066-12, M-S post-production matrix amplifier.
AD146 will accept any combination of M-S and X-Y microphones and mix them in
either the M-S domain or the L-R domain. Therefore the outputs from the mixer may
be in either the M-S or L-R domain. The two domains can be combined to produce
eight possible mixing paths; of these, the following three are the most commonly
used:
(a) M-S microphones (with or without X-Y microphones) mixed in the M-S domain:
output M-S or L-R.
(b) M-S microphones (with or without X-Y microphones) mixed in the L-R domain:
output L-R.
(c) X-Y microphones mixed in the L-R domain: output L-R.
When mixing in the L-R domain and using one or more M-S microphones, the
panpots on M- and S-channels will be centred and the S-switch selected on the
S-channel to create a matrix across the M and S channels. With CH (1) selected
on the monitor module,
MON on an M-channel will audition the M-microphone on
monitor 1 L & R (and headphones L & R) outputs. When 'setting up' M-S
microphones, an S-microphone may be auditioned in a similar manner - BEFORE the
S-switch (15) is selected.
After selecting the S-switch (for S-microphones only),
the complete M-S microphone may be monitored - automatically in L-R stereo. The
potential of such a microphone may be checked by changing the M/S relationship, ie
by varying the input gain of the S-channel. To monitor an S-channel after the S
switch has been selected, CH (1) will reveal +S on monitor 1 left and -S on monitor 1
right - not very useful.
To overcome this difficulty, reduce the right output to zero
and select MONO (14) in order to isolate the in-phase component from the S-
channel.
Spot microphones will be panned to their correct position in the final
L-R image, and may be monitored as non-destructive solo-in-place or as true AFL.