bbystrek wrote:
>
> Hello everyone,
>
> In reading back posts regarding stereo imaging, why does everyone
> appear to be looking to "modify" Crown Audio's SASS product (use only
> their enclosure) instead of also using the PZM mics they offer with
> it? Is it that most of you already own better quality microphones,
> or is there something not desirable about the PZM's for certain types
> of nature recording situations? Or "C", none of the above?
The elements they use are pretty noisy as nature recording mics go. So,
by fitting the enclosure with quieter mics we make something more suited
to nature recording. It's still a form of boundary mic. Lang Elliot's
SASS system uses MKH-20's that are open on front, but the diaphragm is
even with the front face of the enclosure. On the ones I'm building I'm
starting at that point with MKH-110's, but will build a front PZM style
cover with it's narrow gap to examine the difference that might make and
decide which is better.
> I follow the concept of the rubber or foam block simulating a
> binaural experience, but my head's not square (at least last time I
> checked in the mirror). I would of guessed the dummy head variety
> would provide a more realistic recording (perhaps this is not
> necessarily the goal for everyone).
The dummy head provides a realistic recording, but it's hard to create a
listening environment that works for it other than headphones. And
there's the practical disadvantage of cost. The SASS is actually a
hybrid of binaural heads and acoustic barrier setups like the Jeklin
disk, with PZM thrown in. Since it's less sensitive to the type of
listening environment it's got some advantages.
> It seems that in order to capture the amplification benefits of the
> reflected energy, the microphone's element must be nearly (to a
> minuscule dimension for high frequencies on a wavelength basis) at
> the interface in order to benefit and avoid comb filtering boundary
> effects. I'm not sure a microphone assembly with embedded capsule
> allow the reflective surface to get close enough to the energy
> coupling region of the capsule. What do you suppose the test setup
> consists of to look for comb filtering in the frequency response? Is
> it just a matter of getting a calibrated sound source and sweeping a
> tone? Probably exploring the spacial relationships also.
>
> One thing about the SASS concept that sort of confuses me, regarding
> reflected energy amplification, is that how can it be so small
> relative to a parabola, when we need large parabolas in order to
> capture low frequencies effectively?
PZM and boundary effects are a different world and don't use reflections
the same way. Many of your questions will be covered in some detail in
Crown's Boundary Microphone Application Guide, the essential starting
point if you want to get to understand this stuff:
http://www.crownaudio.com/pdf/mics/127089.pdf
I have the same doubts about using complete microphone assemblies in the
SASS enclosure. I do know that Lang's setup does work very well, I've
looked at it and listened to the results. The question is more can it be
made even better?
Crown actually experimented with PZM dishes, but decided it was not a
viable product in the market. I have one of their experimental dish
prototypes and eventually will get around to playing with it. PZM gets
it's gain and frequency response in a different manner than parabolas.
If the dish concept mic appears to have advantages I'll probably try to
design a SASS style stereo setup that uses curved surfaces for it's
boundary. That really will start to look like a set of ears.
Walt
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>From Tue Mar 8 18:22:34 2005
Message: 5
Date: Wed, 31 Jul 2002 04:56:43 +0200
From: Klas Strandberg <>
Subject: Re: AT822 Microphone Noise Floor
Just let me add:
When you have the really "silent microphone" you get into new sorts of trouble!
If you suffer from man-made noise now, like cars and air-planes - just wait
till you want to use the full sensitivity of a really quiet microphone!
Standing 30 meters away from the mic, you even need to hold your breath! Not
to speak about the 30 meters of cable, twisting around in the most
un-expected audible way, when temperature changes. Or tripod noise.... or
the sounds from your own car combustion system, cooling off 150 meters away.
Klas.
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