How does one build a shotgun microphone?

[scottman]

I would like to build a shotgun microphone but cannot seem to find any information anywhere. (Not a parabolic type, for which there is much DIY info, but the conventional long tubular type used in tv/film.) Obviously, lots of design engineers working for established companies (Sennheiser, Azden, Audio-Technica, Shure, etc.) have it down to a fine art, but they're not talking.

Obviously, one could reverse-engineer a good microphone and fake it, but it would leave a lot of unanswered questions about the art/science behind these designs. For example, would one use an omni or cardioid capsule? What should the dimensions of the tube be, and what are the the trade-offs? How do those vents on the sides work? What controls the pickup pattern? The frequency response? Etc. Thanks much.

Scott Morrison
Van Nuys, CA

[Pano]

Good question! The long tube has slots in it to cancel the rear waves. Figuring that out might be hard.

Years ago my uncle built a very strange "shotgun" mic.
It was about 3" around an composed of a series of small tubes. Each was longer than the next, so you had a spiral barrel with the longest tube in the center.

It worked.....

[cbdb]

this is not an easy task. Your basically building an acoustic filter thats directional. For higer freqs a reflector (looks like a small satelite dish) will work and much easier to design

[scottman]

Thanks folks for the responses. Yes, I recall seeing the spiral tube array many years ago.

I agree that figuring it out (from scratch) might be hard, especially for a math-challenged guy like me, but I would assume there are some basic straight-forward design equations published that could be used to determine the physical characteristics of the tube (length, diameter, placement/size of slots, etc), which in turn would be dictated by variables such as desired frequency response, capture ratio, and so forth.

I would imagine equations would also exist for the spiral tube type (how many tubes, what length, what diameter) and the parabolic reflector type (size dish, focal point).

Meanwhile, the search goes on...

[cyclotronguy]

Panomaniac,

The one your uncle built from your description would be a published project from Popular Electronics in about 1966. Used a small speaker element in a household funnel coupled to tubes between 1 inch and 30 inches long. Yes it worked, to some extent.

Cyclotronguy

[jam]

Hey cyclotronguy you are supposed to be busy building speakers....

Jam

[mwmkravchenko]

Hi scottman

If you know how to make a printed circuit board I have a file that you might find usefull from Elektor Electronics 1997 Directional microphone with headphone output.

Mark

[scottman]

Hi Mark,

I really appreciate the Elektor directional microphone circuit offer. Yeah, I'd be curious what that's about. Do you have a general idea of what it consists of? Is the microphone portion of the unit a tubular shotgun type or a parabolic reflector type?

I should mention that the shotgun microphone information I am seeking is more mechanical in nature than electrical (i.e., vented hollow tube), other than what exists in the mic capsule itself.

I have a number of omni and uni-directional electret condensor capsules on hand, most of which I bought from Digi-Key for about $2 each. Ideally, I'd like to build my own poor-man's version of the tv/film "industry standard" Sennheiser MKH416 (>$1000) or equivalent if possible.

Thanks,
Scott

[mwmkravchenko]

It is a tubular type.

I think you have a private e-mail awaiting!

Mark

[deepthrob]

Originally posted by cyclotronguy
[B]Panomaniac,

The one your uncle built from your description would be a published project from Popular Electronics in about 1966.

This one??:

http://www7.taosnet.com/f10/ShotGunMike.pdf

Frank /~ http://newmex.com/f10
@/