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Understanding Stereo Array Performance (was Re: Olympus LS-10 record

Subject: Understanding Stereo Array Performance (was Re: Olympus LS-10 record
From: "Rob Danielson" danielson_audio
Date: Sat Jul 5, 2008 2:10 am ((PDT))
At 1:15 PM +0000 7/4/08, Greg Simmons wrote:
>--- In
><naturerecordists%40yahoogroups.com>=
m,
>"oryoki2000" <>
>wrote:
>
>>  In my brief experiences with small recorders, the LS-10 stands out
>in
>>  the way its built-in mics produce a "wider" soundscape. Most small
>>  recorders have mics that point forward, parallel to each other. The
>>  LS-10's mic capsules, in contrast, point away from each other in a
>90
>>  degree spread.
>
>The LS10 uses a technique similar to one mentioned by the late great
>Michael Gerzon in an article about stereo shuffling and spatial
>equalisation published in the July 1986 issue of Studio Sound
>magazine. This involved two cardioids crossed around 115=B0 to 120=B0,
>facing outwards, and spaced 5cm apart. The LS10's quoted width of
>48mm puts the capsules the right distance apart, although they seem
>to be at a narrower angle than Gerzon suggested (which may strengthen
>the centre image a little due to it being less off-axis).
>
>According to Gerzon:
>
>"Remarkably, for normal stereo listening configurations, it turns out
>that the 5cm spacing produces roughly the same phase/amplitude
>relationships between the two ears of a listener in the stereo seat
>as does a live sound from the same apparent direction up to about
>2kHz =96 and in this respect is better than true coincidence. Such 5cm-
>spaced crossed-over cardioids, angled about 115=B0 to 120=B0 apart, seem
>to be an optimal cardioid technique for stereo imaging accuracy."

http://www.audiosignal.co.uk/Resources/Stereo_shuffling_A4.pdf

>
>Perhaps this explains the LS10's impressive stereo imaging
>capabilities?

The capsule types and mathematics could be close.
Vicki's 183's seemed to l spread. That's just one
attribute among many (but it was the most obvious
and it isn't that obvious).

Rich Peet and I spent a day testing three arrays
in a quiet, snow-blanketed hollow and I made this
video:

Each of use preferred a particular array and
often our reasons would contradict.  People who
want to al

  that Vicki tested had better spatialization. See what you think?





better localization than the built-in mics. Most
stereo arrays should be able to portray what Greg
Peterson and I were able to assess in his
LS-10/built-in recording. There are many
qualities on can listen for stereo imaging beyond
this and difference in monitoring will play a
huge role in people's final preferences. Stereo
imaging is probably a lot trickier to evaluate
"universally"  than qualities like mic self-noise
and mic pre input noise. We can also ask maby
different things from stereo from represebtaion
of acoustic space to dramatic effects. And think
of how differently we often interpret tests.


>
>Interestingly, Gerzon's article also mentions the technique of
>spacing the mics a small distance apart and angling them inwards (as
>used in the Zoom H4), but suggests that although it livens up the
>sound, it degrades the stereo imaging - something my own experiences
>with the H4 agree with.
>
>- Greg Simmons


I would very much like to enjoy a much better
perceptual understanding of the precise qualities
afforded by the many stereo arrays there are to
work with. Rich Peet and I set-out a large test
area last February in a quiet location and tested
three arrays for localization and depth with
sounds from 100' out to 700'.  The arrays seem to
have much greater differences in imaging than I
expected and it was tempting to draw
conclusions/preferences. It taught me that  from
the It wil take a quiet location in order to
discern the subtleties and provide enough
matching bacjground to be able to exhaustively



really  of Now that I live in a quiet location, I
want to set-up an array of speakers so that I can
start testing stereo and surround array imaging.
There are quite a few folks who avidly pursue the
principles Gerson laid-out. I've not been able to
test how this approach compares to arrays that
use head-spacing.  Most of them rely on
processing applied to already recorded files
including complex ones as with ambisonics and
simpler ones like M-S. I'd like to hear that they
work marvelously, but every time I've had a pair
of good headphones on and field tested many
placement options, separations that were ear
spaced or larger produced better localization,
depth and realism. In my opinion, Vicki's recent
DIY 183 rig is another example among many.



>
>


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