Fascinating MS
"Tom McCreadie" wrote in message
...
"Gary Eickmeier wrote:
"Scott Dorsey" wrote in message
...
Decoded MS and coincident cardioids are mathematically identical and
they
are very close to interchangeable with top-grade microphones. As you
get
to cheaper microphones that are less flat off-axis, the X-Y
configuration
becomes more of an issue since the center of the soundstage is off-axis
on
both mikes.
In other words, coincident XY is the same as MS with the M and S about the
same gain, and also the XY can be converted back to an exactly equivalent
MS
pair that can be manipulated just as if the original were MS (?).
No, the gain doesn't come into it. You are reversibly and losslessly
"translating" all the stereo information data from its listenable X/Y
format
into a not-directly-listenable M/S format (All the information in the MS
format
is available to re-create the XY.)
The ratio of M to S that happens to result from the XY - MS operation
will
depend on (a) the polar pattern of the XY mics and (b) their angular
splay. And
as a corollary, the pattern and splay of a (virtual) XY pair is driven by
the
(a) the chosen M mic polar pattern and (b) the M to S ratio. This "about
the
same gain" is irrelevant.
Think of XY - MS as a sort of translation process. Take a word "tree";
translate that into French using your an En-Fr dictionary; that may be
unrecognizable for your kids, but once they consult a Fr-En dictionary it
all
becomes perfectly clear again.
Many folks have a persistent notion that only MS allows width adjustment
(via
gain ratio changes.) Any coincident XY array can do that...just that it's
a mite
less convenient, entailing an extra step:
MS - XY
MS - ratio change - M'S' - X'Y'
XY - M/S - ratio change - M'S' - X'Y'
Well, I am not sure how to word my question, but when you buy an MS recorder
like the Zoom H6 with built-in MS module, you get an adjustment that goes
from Zero dif between M and S in the plus direction all the way to RAW and
in the minus direction (less and less S mike) to zero, or mono. This
suggests that (if there are sounds all around you, not just a solo
instrument up front) that the S = 0 would have both M and S gains equal,
right? Then at that time the MS pair would be exactly equivalent to the XY
Blumlein pair. But with other polar patterns for the M mike than Fig 8, this
equivalency might not hold. Also interesting that coincident stereo is pure
intensity stereo and is subject to this mathematical translation, but does
that hold true for any of the spaced microphone techniques? I mean,
obviously the signal doesn't know how it was obtained, so you could do the
stereo width control on any stereo signal, right?
I guess I should just record my MS in RAW and do as I please with it later,
but I have always wondered how I should ideally be setting my gains while
recording. Should I set both M and S knobs the same and let the signal rise
and fall where it may, or should I set them so that both tracks are equally
loud most of the time? Would that be equivalent to setting the Zoom S signal
to zero difference from M?
Fascinating stuff. And yes, I have and still am reading all about it. I
would normally think that a little spacing between mikes would add something
to the stereo mix (over the coincident techniques), but in practice so far
MS has it hands down in both accuracy and spaciousness.
Gary
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