This is only true IF the two mics are of equal sensitivity, recorded
with equal gain, and pass through the MS Matrix with equal gain. Thus
decoded, the MS will provide a 90 degree stereo image. But reducing
the amount of the side signal, will narrow the field. Thus removing it
will leave you only the mid mic, or 0 degrees... so less signal of the
side mic will narrow the field. At 1:1 you have 90 degrees. Beyond
that, if you increase the level of the side mic over the mid mic, you
start playing with weird phase, and the image may 'sound' even wider,
as is the effect of out of phase signals, getting that sort of 'washy'
sound thing...
It's also worth noting that even with the identical field, 90 degrees,
the 'sound' may not be the same. It depends on how smooth the off axis
characteristics of the mics are. Also a figure eight design rolls off
naturally above 16kHz, which could affect the stereo image.
We did some tests comparing one of my Schoeps MS rigs against a
friend's Schoeps XY rig, and found at 1:1 they did sound nearly
identical.
I guess the other thing to note is that a figure eight design tends to
be noisier than a cardiod, which is noisier than an omni. So an XY rig
could be quieter than an MS rig.
On Mar 7, 2008, at 8:17 AM, Scott Fraser wrote:
> To clarify a bit, decoded MS provides EXACTLY the same stereo field
> as XY (coincident 90=B0 cardioids).
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