Well I guess I will weigh in on this topic. I built one of these in 1957
because shotgun mics and parabolas were not available at affordable prices
for my project. I was 10 yrs old at the time. I wanted to detect human
voices, not birds. I think it works pretty well for voice stuff and my
understanding is that in the 1950's, when I built one, this was one of the
few ways to go for mechanical amplification. I don't know when modern
shotgun mics were invented, but they would have been pretty pricy back then=
.
Getting a parabola during the same era would also have been expensive, if
you could find one at all. Parabolas were certainly around back then, but i=
f
it cost a few hundred dollars that was a fortune. A good car cost a few
hundred dollars. Today, there is no advantage for natural sound recording
because flat frequency response shotgun microphones allow quiet electronic
gain to be applied to the signal. A parabola has all kinds of non-linearity
compared to the microphone, but is considered a wonderful tool nevertheless=
.
The tube amplification will produce a whole series of holes in the frequenc=
y
response and will probably produce something so non-linear that the defects
could not be removed without a lot of work. I think this technology would b=
e
good to use as a historical comparison technology to show how far we have
come in the last 50 years and it would be interesting physics project for
the public to see in a sound museum. But for real recordings, its day has
passed.
Greg Clark
-----Original Message-----
From:
On Behalf Of Michael Oates
Sent: Friday, September 07, 2007 10:44 AM
To:
Subject: Re: [Nature Recordists] Re: Machine Gun microphone
Hmmm, Not sure if I want to go ahead with this if I am going to get lots of
the spectrum
missed in the recording. The way I would build it, it would not be cheap. I=
f
I start to
add up all the extra bits apart from the tubes, =A3200 is a more likely
figure, so not
exactly cheap just to try! And it would take a few weeks to make.
I would like to hear from someone who had had some success with this type o=
f
microphone,
especially if comb filter effects can be avoided. This could be the reason
why information
on this type of mic is hard to find and is widely being used.
Thanks,
Mike
>I have had one of these since the 1970s. Built it from plastic
>piping, and was never happy with the performance, but it does work.
>It was the original shotgun microphone for those with little money.
>Mine was originally built for a limited spectrum of sound with quite
>a few fewer tubes than the project you plan. They are a fun project
>if you want to try one. I'd be interested in how your project turns
>out.
>
>--- In "Michael Oates" <>
>wrote:
>>
>> Has anyone every made and used a machine gun microphone. There is
>not
>> much about these on the internet, but I have found this:
>> http://www.reject.org/tsd/liz/gbppr/mil/mic/ShotGunMike.pdf
>>
>> I am concidering making one using 90 tubes of 8mm diameter
>aluminium
>> tube with lengths from 1m down to 9mm. (That is two more rings of
>> tubes than shown on the example making it 88mm diameter instead of
>> 67mm) I was thinking of fitting a Rode NT1A as the condenser mic.
>But
>> I really want to know if anyone has tried such a beast. Based on
>the
>> length of tubes I would use, it should work from about 150Hz to
>20kHz
>> range and appears to be very directional.
>>
>> My idea of using more tubes that in the example it to fill in the
>> gaps in the frequency range, but I don't know if that's needed.
>>
>> Cost would be about =A3120 for the tubes plus a bit more for for
>> fitting some windshield around it with fake fur on a wire frame
>> former covering the full length.
>>
>> Thanks,
>>
>> Mike
>>
>
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause
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