[nebulax]

I was just looking at some pictures and specs for the new A-T BP4025 X/
Y stereo mic, and something struck me as kinda odd. The capsules are
almost back-to-back; not angled a full 180 degrees apart, but maybe
140 or 160. Doesn't an X/Y pattern usually work at 90 degrees, or so?
Even if the capsules are that close together, won't there be a bit of
the 'hole in the middle' with a severe angle like that? I could see it
working if the individual mic patterns were omni (creating sort of a
binaural effect), but with cardioids it seems a little extreme.

-Neb

P.S. Here's a link to A-T's page for that mic -
http://www.audio-technica.com/cms/wi...6a2/index.html

[Scott Dorsey]

nebulax wrote:
I was just looking at some pictures and specs for the new A-T BP4025 X/
Y stereo mic, and something struck me as kinda odd. The capsules are
almost back-to-back; not angled a full 180 degrees apart, but maybe
140 or 160.

The patterns of the capsule aren't symmetric either... look at the
baffles on each capsule and they are not radially symmetric at all.
This is the secret to these things.

Doesn't an X/Y pattern usually work at 90 degrees, or so?

More or less, BUT since there are no phase differences between channels,
you can make the narrower or wider and then adjust the L-R component
to get the stereo image right. The problem is that if you take two normal
cardioid capsules faced out at 180' and reduce the stereo width, you have
the majority of the stereo image in the least-accurate part of the capsule's
polar pattern.

Even if the capsules are that close together, won't there be a bit of
the 'hole in the middle' with a severe angle like that? I could see it
working if the individual mic patterns were omni (creating sort of a
binaural effect), but with cardioids it seems a little extreme.

The capsules on those mikes are not cardioid. They aren't omni either,
they are something weirdly shaped and specifically designed for the
application.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[nebulax]

On May 25, 8:37*am, (Scott Dorsey) wrote:
nebulax wrote:
I was just looking at some pictures and specs for the new A-T BP4025 X/
Y stereo mic, and something struck me as kinda odd. The capsules are
almost back-to-back; not angled a full 180 degrees apart, but maybe
140 or 160.

The patterns of the capsule aren't symmetric either... look at the
baffles on each capsule and they are not radially symmetric at all.
This is the secret to these things.

Doesn't an X/Y pattern usually work at 90 degrees, or so?

More or less, BUT since there are no phase differences between channels,
you can make the narrower or wider and then adjust the L-R component
to get the stereo image right. *The problem is that if you take two normal
cardioid capsules faced out at 180' and reduce the stereo width, you have
the majority of the stereo image in the least-accurate part of the capsule's
polar pattern.

Even if the capsules are that close together, won't there be a bit of
the 'hole in the middle' with a severe angle like that? I could see it
working if the individual mic patterns were omni (creating sort of a
binaural effect), but with cardioids it seems a little extreme.

The capsules on those mikes are not cardioid. *They aren't omni either,
they are something weirdly shaped and specifically designed for the
application.
--scott

--
"C'est un Nagra. *C'est suisse, et tres, tres precis."



Yeah, now that I look at the photos of the capsules again, the front
plates have a weird pattern to them. I guess when you make almost
every piece of a mic assembly, you can customize the parts a bit.

-Neb

[Scott Dorsey]

nebulax wrote:

Yeah, now that I look at the photos of the capsules again, the front
plates have a weird pattern to them. I guess when you make almost
every piece of a mic assembly, you can customize the parts a bit.

AT did really well with these things. Not only is there an asymmetric
resonator in front of the capsule but the backplate on the capsule is also
asymmetric. I'd love to see the modelling that went into these.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."