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Re: hat mic

Subject: Re: hat mic
From: "Rich Peet" <>
Date: Sun, 11 Jul 2004 15:39:06 -0000
The reason I did not go over three elements is cost and impedence.
As you increase the number of elements you have to start considering 
a transformer to bring the impedence back in line.  With a Sony MD 
that means about 5,000 ohms which means a transformer would already 
help sensitivity with just one element.

On phase you start to have problems when arrival of the sound at 
different elements is more than 90 degrees out of phase. At 10,000 
cycles the wavelength is 1.356 inches. 90 degrees would be 25% of 
that or .34 inches. So my design with stacked elements are ok even 
for an overhead bird but sound is still maximized for horizon 
recording where the sound is arriving at the mics at the same time.

For a calculator see: http://www.mcsquared.com/wavelength.htm

Sorry never heard of a sweet 16 but odd vs even number of elements is 
not a factor.
Rich

--- In  Jim Lee <> wrote:
> Can someone give a brief overview of the use of multiple capsule 
arrays. 
> I am wondering at what point you reach a point of diminshing 
returns. 
> What about the phase cancellations? Would circular arrays help or 
hinder 
> the problem? What is the effect of capsule size on phase problems? 
Odd 
> vs even numbers?
> 
> I recall experimenting with a four by four small speaker array 
called 
> "Sweet Sixteen." I think it was from Popular Mechanics or some such 
> magazine years ago. Would there be any advantage to making a "Sweet 
> Sixteen" microphone array?
> 
> Jim Lee
> 
> Rich Peet wrote:
> 
> >Three capsules are soldered in parallel per each channel and sewn 
to 
> >the sides of a wide brim hat. 
> >
> >Mics were sewn in a verticle arrangement to minimize any possible 
> >phase problems.
> >  
> >
> -- 
> 
> Jim Lee - Bamboo Turtle Studio
> http://www.bambooturtle.us/
> 919 682 5853
> audio art, gourd sculpture,
> lighting design, and forensic audio
> Co-Curator: upstART Gallery
> http://www.upstartgallery.com



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