marileau
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What is a shotgun mike?
Shotgun Mike
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Super directive pickup garners objective sound in loud environments. Shakeproof holder works as a dampening mechanism to cut case and handling noise. Uses a AA battery, 600 ohm input, 50-10,000 Hz response. With windscreen and case. Can be used with our HGA90 high gain amplifier. Can hear normal conversations from ~50-75 yards away.
Jim<
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Gosh i thought it was the name for a new western movie
My camera had a Senheiser shotgun mic. They gave them to all the photographers as a bonus when we won NPPA's News Station of the Year. They had a foam rubber windscreen. It really enhanced capture of natural sound. They were also used as interview mics when you were working one man band style (99% of the time for me) in a pinch. I prefered a EV 635 for one on one interviewing with the shotgun in the other channel for back up, selecting the clearest audio in editing. The shotgun would not pickup questions if the photog was doing the interview, sometimes a good thing.
Its actually easy to make your own shotgun mic, and make it better (i.e. longer) than what's typically commercially available. All it is is a tube with about 20% or less of its surface area perforated regularly along its length (including the boresight end--which can be closed or have a small hole in it). A higher percentage of surface area perforated reduces directivity and, of course, pipe rigidity, less perforations reduces sound power. So that's why I gave the 20% figure. Install one or more electret mics within one end. Each time you double the number of mics, you improve SNR by 3dB--so you can buy several electret mics and series them (watching mic polarity!) for better SNR and higher signal voltage. they don't all need to be facing forward, and they should be no further apart than about a quarter-wave of your highest freq. Be sure the back-end of the pipe (where the mics are) is closed. Also, remember to adjust the mic power supply voltage and impedance accordingly (each mic is typically 4K ohm impedance and needs a few volts bias, resistor limited!). You might consider using a thin-walled 1" aluminum or plastic (but which might have a sag problem) pipe. Ideally the length needs to be several wavelengths of the lowest frequency you want to pick up directionally. Of course, that gets unmanageable very quickly trying to get directivity at 100Hz! So most good commercial shotgun mics are no longer than a couple feet. Additionally, since directivity increases with frequency, you can tailor the placement of the perforations to reduce directivity for higher frequencies just to keep the spectrum flat (I ~think~ that means smaller but closer holes closer to the back end, but I'm not sure ATM)--but that's not always necessary, especially if directivity is more important than getting the right spectrum. be sure the mount reduces vibrational noise, since you'll probably need to crank up the gain.
Waves arriving at any angle other than boresight will experience destructive interference within the tube.
Waves arriving at any angle other than boresight will experience destructive interference within the tube.
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marileau
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marileau
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Thank you digproc
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