David Satz wrote:

So in general, I favor using a supercardioid "M" microphone. If I have
to cover so wide an area that I can't use that narrow a pattern, then a
centered, coincident stereo pickup probably isn't the best idea anyway
(unless mono compatibility is an absolute requirement).

If you think of the cardiod family M as a figure 8 summed
with an omni and if you match the gain of the figure 8
component with that of the side, then the sum and difference
that do the MS - LR encoding just create a left figure 8
pointing at -45 and a right figure 8 pointing at +45 both
superimposed with the omni component of the M mic. The
ratio of that omni component to the figure 8 is what
determines where in the cardiod spectrum the real mic and
virtual LR mics fit (hyper, super, card, sub, hypo.)

If the fig 8 sensitivities are matched between mid and side
and the M is a true card then the +-45 degree virtual LR
mics will be hyper cardiod because their fig 8 components
will have sensitivities that are the sqrt(2) times that of
the actual mics while the omni component is one times the
omni component of the mid. Thus, going somewhat
hypercardiod with the mid, as you suggest, makes the virtual
LR mics even more hypercardiod.

In practice, the M and S sensitivities are nowhere near as
carefully controled if one is setting one's own relative MS
gains and it is virtually impossible to say what virtual LR
patterns you have. For that reason, you experiment, listen
and tweak. :-)

If you further take into consideration that these patterns
are highly frequency dependant, even if symmetric front to
back, then it is _very_ hard to generalize what you get from
a coincident (intensity based) stereo configuration, MS or
XY. That's not to say, however, that they can't sound great.

One thing I have not been able to get away from with MS or
XY is that if I have a drum kit that is a fair bit to the
side then the image separation between the kick and cymbal
is very highly exagerated and the cymbal can even swap
sides. This is because of the frequency dependant patterns
and because phase matching becomes very important at the
higher frequencies due to the MS-LR summing.

The more I study this stuff the more I come to realize that
there really isn't a theoretical basis for stereo
configurations that holds any water because all the premises
of the theories are idealizations that are terribly far from
reality. It's all hueristic in the end. Try things without
much worrying about what is right or wrong and see what you get.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein