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Re: Stereo Microphone Placement

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Scott Dorsey to Fred McKenzie:

> > I  am  attempting  to  set up a couple of micro-
> > phones to record an Orchestra  performance.   In
> > order  to achieve a stereo effect, it was my im-
> > pression that the microphones should  be  spaced
> > several feet apart, one on each side of the cen-
> > ter of the stage.
>
> This is called A-B stereo.

Only if  the  microphones  are  omnidirectional  and
placed  closer  together,  usually  about  20-30 cm,
which is about the ear-to-ear distance.   The  musi-
cians  are positioned within a 40-degree angle.  One
may achieve it by varying the distance.

Other combinations of distance and microphone  spac-
ing  are  possible,  but  then you risk to get nasty
comb filtering or poor spatial impression:

           S = L * sqrt( 1 + ( 2d/w )^2 )

where S is microphone spacing, d the distance to the
source,  w  the  width  of  the  source,  and  L the
wavepath that crates a phase difference perceived as
the  location  of the source directly to the left or
right.  It may be estimted from  the  recommendation
above:
              25 * sin 20 = 8.55 (cm)

> It  gives  you some intensity imaging but no phase
> imaging because the phase differences between  the
> channels are too great for the brain to make sense
> of them.  It was very popular back  in  the  1950s
> and  1960s  when  good directional microphones did
> not exist and omnis were the order of the day.

True A-B technique (with smaller spacing) is  purely
phase-based  stereo, which is the only right kind of
stereo because it imitates human  hearing.   Another
great  phase-based technique is SASS, which does not
suffer from the  A-B  limitations  mentioned  above.
But   unfortunatly   the  overwhelming  majority  of
mordern recordings  are  made  using  polymicrophone
technique and consequenty intensity-based stereo.

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Thread

Re: Stereo Microphone Placement Anton Shepelev <anton.txt@gmail.com> - 2017-01-11 16:23 +0300
  Re: Stereo Microphone Placement Fred McKenzie <fmmck@aol.com> - 2017-01-11 12:06 -0500
    Re: Stereo Microphone Placement kludge@panix.com (Scott Dorsey) - 2017-01-11 14:03 -0500
      Re: Stereo Microphone Placement Fred McKenzie <fmmck@aol.com> - 2017-01-12 11:39 -0500
    Re: Stereo Microphone Placement Anton Shepelev <anton.txt@gmail.com> - 2017-01-12 19:35 +0300

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