Audio Developments AD144 - Manual (Page 36)

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matrix amplifier. For any L-R stereo signal appearing on the monitor modules,
DEC (15) will reveal mono capability (M) on monitor 1 left module and out-of-phase
components (S) on monitor 1 right module. These signals may be isolated by
selective use of the monitor 1 output faders.
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 in
the 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.
AD144 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 or both, simultaneously; similarly, the mixer
outputs may be in either or both M-S and L-R domains. 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. 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 (23) is selected. After selecting the S-
switch (for S-microphones only), the complete M-S microphone may be monitored -
automatically in L-R stereo - MON selected on both microphone channels and CH (1)
selected on BOTH monitor modules. 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) on
BOTH monitor 1 modules must be selected although only the in-phase signal should
be auditioned - reduce to zero the fader of the right hand monitor module.