> Heres a demo:
> http://soundcloud.com/urlme/wood-spherical-baffle-rig-vs
>
> WSB is two wood spheres mounted in a rode blimp aka AB stereo.
>
> The two planar transducers are figure 8 dynamics (flat coils not
> ribbon mics) and theres still plenty of ambience there.
Mike,
First off what planar transducers are you using? What's the specs?
I like listening to experimental stuff. It checks out the theory and
my prejudices. :-) I predicted that the wooden spheres would give a
mainly HF stereo effect and that the stereo on the parallel
bidirectional pair would be reduced.
On listening I am surprised at the quality of the Faulkner. It had a
clarity which was lacking in the spheres, which sounded a bit -
sorry - wooden. :-) The stereo image of both was limited and the
traffic noise was nebulous and "phasey". Don't know why - just not
focussed. I would suspect reflections between the inside of the
windgag blimp and the spheres. We pay three zeroes for our mics and
then put them inside a babygro. :-) I know, I invented the original
outer Brinisock.
With the Faulkner, I didn't expect a wide image angle, and it sounded
limited to about 45 deg either side. Time Stereo does need a bit of
help from amplitude stereo as well, but the front stereo image was
much better than I expected. 20cm is wider than dummy head spacing but
how wide are the transducers themselves? If they are significantly
wide, some of the theory goes out of the window. :-)
For analysis. I derived M and S signals (thanks for making it
downloadable) The S signal from the spheres was mainly mid to high
frequencies, leaving the bass end to the M. The overall effect was a
limited stereo width, a bit of muddiness and some out of phase
backgrounds.
The Faulkner S had quite a lot of bass in it, giving a bass spread in
the stereo image. Good thunder. The M was nice and clean, especially
with the thunder. Rain and foreground sounds were sharp and well
placed with background noise - traffic - fuzzy, but not a problem. I
think a 45/45 Blumlein pair would have given a wider image, so objects
at 45 would map to 90 ie full left or right, but it would also have
given a 360 deg pickup with out of phase sides.
The directionality of the Faulkner is limited to a vertical doughnut
of reduced sensitivity, but this may have limited the tree noise and
ground reflection and improved the overall clarity. The good news is
that the rear pickup remains mainly in phase. There is a general bias
in the stereo towards the left - is this the tree or trees? The
thunder is well placed, so I assume that was left, mid and right as it
sounded.
To see what the object/image relationship is like, do a walk-around
like my shaking peanuts test, or use s fixed multi-frequency source
like a running engine and rotate the mic rig slowly. I'd predict that
the image angle would generally be smaller than the object angle (for
example a 180deg spread comes out as a 90deg spread) and
that the sensitivity would fall off from about 70 deg each side.
The Faulkner rig defeated some of my prejudices, but remains best
heard binaurally. It gave stereo on close speakers, but was better on
cans. I doubt if it would work as well on a room hi-fi setup. The maim
snag I can see for wildlife use is its rear sensitivity. Indoors it is
going to pick up a lot of unwanted reverb.
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
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