> From: umashankar <>
> Subject: Re: SASS
>
> years ago in studio sound, they ran a comparison of
> various PZM (or boundary layer) microphones.
>
> i prefer the word boundary layer.
I use PZM only to designate the ones that have the diaphragm facing the
boundary with a space designed to control frequency response. Boundary
for the other designs that are sampling the boundary effect. This seems
to be the way Crown does it. They actually own the designation PZM, so
other companies may be using their mics PZM style, but call them
boundary mics.
> anyway, one point made in that review was that at the
> boundary layer, it should not matter which way the
> mike points - towards the surface, just a tenth of an
> inch or so away )aka pzm) or mounted flush, facing
> out.
I'd read all that when I made my SASS, but had to try it for myself
before I was willing to believe it. Still does not seem logical, but
whatever works.
> i start builing my mikes with the capsule flush
> because it was a lot easier.
For sure, it was a real hassle designing a PZM cap system for the SASS.
> and then i started mounting several on the same plate
> (i tried 11 capsules once, but now build with only
> five) and the found the beam narrowed, from 180
> degrees to about 30 - 60 degrees at mid to high
> frequencies.
That's very interesting, I don't think anyone has mentioned that before,
though my memory is hardly perfect. Usually the reason for multiple
capsules is to get low noise and high gain.
> i have then mounted this plate facing into a parabolic
> reflector of about a foot in diameter.
I do hope you are going to let us know the details of how it's working.
In particular I'd be interested if it's still working for lower frequencies.
Walt
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