Fascinating MS
Gary Eickmeier wrote:
Are you guys thinking that M will be stronger because it is pointing
straight at the music, whereas S is just doing the sideways ambience? I
smell a rat somewhere in there.
In a typical array placement in an auditorium, most of the sound energy will be
direct sound arriving predominantly from the front. The sounds from side and
rear will be predominantly lower level reflected sounds etc. Why do you find
that so surprising?
So two questions:
1. What would the M and S gains register on the meters for a source exacty
45° from straight ahead? Equal, right? Admittedly, to this will be added the
straight ahead sources, which will be in the null of the S mike, but then
answer #2:
It depends on the pattern pf the M mic:
_____________________________
45 deg. off-axis M pattern
dB drop
_____________________________
0.00 Omni
0.88 Subcardioid ("V = 0.67 + 0.33.cos.theta")
1.38 Cardioid (Zoom H6 M/S module ?)
1.77 Supercardioid ("V = 0.37 + 0.63.cos.theta")
3.01 fig- 8
______________________________
2. If you were doing Blumlein with two figure 8 mikes, the two channels
would obviously be equal. In this case, a source at 45° would be max in one
channel and in the null of the other. Question 2: What would the
mathematically equivalent MS signals look like? I'm too tired to think right
now, but wouldn't that answer the musical question? Isn't that what the Zoom
H6 is doing with the S set to zero dif from M? That would be knob setting,
not actual levels of course.
If you take a stereo signal from a conventional +/- 45 deg. Blumlein pair and
perform a standard MS operation on it, the resultant signal - if still played
back as an XY signal - would be what would have come from a Blumlein pair aimed
45 deg left ("North-West") - but with the L and R ouput channels swapped. Clear
as mud? :-)
As for your Zoom H6 M/S module, let's assume firstly that the M mic is a
cardioid pattern and that it has the same sensitivity as its S partner. Then an
M/S with a cardioid for M and at 1:1 M:S gain setting translates mathematically
to a virtual XY array of two supercardioid mics (pattern: V = 0.31 + 0.69
cos.theta), splayed at 127 deg. included angle Such an array would have an SRA
of ca. 85-90 deg.
--
Tom McCreadie
"Ah, where would we be without humour." "Germany?"
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