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Old 11th February 2006, 09:02 PM   #1
wxn is offline wxn  Lithuania
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Default Some shotgun mic ideas

So I decided to make a shotgun mic. Something like this:
http://members.shaw.ca/roma/shotgun-2.html
Now, the original design has only one mic for all tubes which are effectively open-ended resonators. But if we close one end, we get quarter wave resonators and effectively half the size. But the only reasonable way to close one end is to physically put an electret mic capsule in each of these tubes. Possibly applying Linkwitz mic mod, buffering, equalizing and then mixing all the signals together.
All this might work but I'm not sure about noise performance. I mean, each active conponent and each resistor contributes noise to that extremely low level signal. But then again, multiple signal sources across the working range could bring some benefits too.
The question is, is it worth to "electrify" each resonator just to reduce size and have all the possible problems with noise and complexity. Or is it way better to just make some sort of reflector and amplify one capsule?
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Old 14th February 2006, 04:14 PM   #2
vmike is offline vmike  United States
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I built that very mic from the same article 35 years ago. As I recall the only modification I made was to the funnel allowing for installation of various microphones. The mic I liked best withit at the time was an Electrovouce EV-635. I don't really remember there being any noise problems, even wind noise was minimized. Although the assembly was damned heavy being made of electrical conduit.

Anyway,

mike
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Old 18th February 2006, 12:31 PM   #3
wxn is offline wxn  Lithuania
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Great to hear that I'm not the only one wishing to build this thing
Anyway, does anybody know why the resonators are cut in linear manner and not logarythmic? AFAIK given that diameter of the tubes remains the same, we have the same Q. Cutting them in linear steps gives a very uneven frequency response and weird phase distortion..
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Old 18th February 2006, 12:41 PM   #4
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sounds a bit complicated depending on ho many resonator's you were thinking about...

I wouldn't worrie about noise (resistor&transistor) too much .. the electret it self has a pretty high (? 20 - to - 50nV/sqrtHz?) noise voltage.. besides that .. you could put band pass filters on all of them.. .. then in theory the noise should increase at all....

I have build various binaural mics with the panasonic electrets and they are notouriously windnoise sensitive
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Old 18th February 2006, 02:40 PM   #5
wxn is offline wxn  Lithuania
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Nothing complicated, I've already built and tested a mini version of this thing with only 7 tubes works nice, but only for the higher frequencies.
Band-pass shouldn't be a problem, just a pair of capacitors there and there in the preamp and voila. Wind noise shouldn't be too much of a problem either as I'm gonna put the whole thing into a larger tube with sound/wind absorbing material inside.
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