M/S (Sum & Difference) Modes; Stereo Width Effect Using M & S Signal Encoding; M/S Decoder - Euphonix CS3000 Operation Manual

Section 4: Tutorial
M/S (Sum &
Difference) Modes
Stereo Width Effect
Using M & S Signal
Encoding

M/S Decoder

4 - 58
The comprehensive internal routing structure of each channel allows for some
interesting operational modes with M (Left and Right mono sum) and S (Left &
Right difference) signals.
This is where a stereo signal is fed into the channel and split up into a mono
sum and a stereo difference signal. The amount of stereo spread can be
adjusted from mono, to normal stereo, to extra-width stereo, with no effect on
mono compatibility.
The best way to experience this is to try it with any stereo source. Patch up
the left (A) and right (B) signals as shown on the next page, using the upper
parallel feed jacks on the half-normalled patchbay to send the left signal to
both M1 and L2 inputs. Patch the right signal to both M2 and L1 the same way.
Select the upper and lower fader sources as shown (i.e., M1, M2, L1, & L2 to
the upper fader, and L1 & L2 to the lower fader). Set the upper fader pan/bal
mode to 10 (Stereo Reverse) and the lower mode to 6 (Mono without pan).
If you only have the lower fader up then you will hear a mono signal. As you
add more of the upper fader, the summed signal changes from mono to normal
stereo (when both upper and lower fader gains exactly match). Increasing the
upper fader even more begins to give you an extra-width stereo image, but
with complete mono compatability.
You can check the mono compatability by switching the monitor outputs to
mono and moving the upper fader up and down. You will notice that this has
no effect on the mono output.
M1 and M2 must also be set to exactly the same gain as L1 and L2. As L1 and
L2 are set for +4dB input, make sure the gains in M1 & M2 blocks also show
+0.0dB in the SmartDisplay menu (+4dB with gain controls fully counter-
clockwise).
You should adjust the upper fader stereo balance control while listening in
mono, only to the upper fader signal, to get a minimum signal. This ensures
that the M1 & M2 inputs feeding the upper fader sum equally.
The signal diagram at the bottom of the next page shows how you can decode
an M & S signal into Left and Right signals. Note however that if this is an M
& S microphone pair, the console cannot provide phantom power to both mics.
Make sure that the M1 and M2 gains are set exactly the same as the L1 and
L2 gains. This may require an external mic preamp to get the L1 and L2 gains
hot enough.
In both these examples you can use L3 and L4 instead of L1 and L2 if you wish.
Euphonix CS3000/2000 Operation Manual