Audio Developments AD149 - Manual (Page 72)

71
MIXING
We have already established that, during post-production, it is desirable for signals to
be in the L-R domain at the input to the fader of stereo modules - but not necessarily
stereo pairs of mono modules - in order that auxiliaries shall be meaningful.
(Refer to page 53)
During recording/production there are eight possible signal paths through the mixer:
inputs to the module in M-S or X-Y; mixing in the M-S or L-R domain; mixer output in
M-S or L-R. (Refer to FIG 17) Whichever path is selected, no constraints will be
placed on the auxiliaries as mixing in the M-S domain is a legitimate technique.
When auxiliaries are not being used for usual applications, they may be used to
create a mix different from the main mix; or identical with it - but in the opposite
domain. A recording made in the M-S domain will be ready for the application of
all possible post-production techniques.
Of the eight paths through the mixer, we believe that numbers 1, 2 and 3 will be the
ones most frequently used, with 4 & 4a having no likely usage. (When using stereo
microphones, it must again be stressed that odd-numbered modules are occupied by
the X/A/M microphone and that even-numbered modules are occupied by the
Y/B/S microphone.) A combination of M-S, X-Y and spot microphones may be mixed
either in the L-R domain or the M-S domain. (In each case the stereo microphone
must be matrixed to the appropriate mixing domain.) When all inputs are in X-Y form,
mixing will normally be done in the L-R domain.
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.
Any M-S microphone (or input) will be in the M-S domain at the pre- and post-fader
auxiliary points. M-signals may be mixed on AUX 1 and S-signals on AUX 2, then
matrixed to L-R on the auxiliary outputs. Alternatively, a L-R signal may be recorded
from the main output, and an M-S signal from the auxiliary outputs. Spot
microphones would be added only to the AUX 1 mix.
When mixing in the L-R domain and using one or more M-S stereo microphones, the
panpots on M- and S-channels will be centred and the S-switch (15) selected on
the S-channels to create a matrix across the M- and S-channels. With CH (1)
selected on the monitor module, MON on the M-channels will audition
an M-microphone on monitor 1 L & R (and headphones L & R) outputs. When
'setting up' M-S microphones, the S-channels may be monitored in the same manner
- BEFORE the S-switch is selected. After selecting the S-switch, the
complete M-S microphone may be monitored - automatically - in L-R stereo. At this
stage, the potential of these M-S microphones may be checked by
changing the M/S relationship, ie by varying the input gain of the S-channels.