Bazooka mics

[Nick Flowers]

OK, this is going back a bit and I may have the details a little wrong, but I vaguely remember seeing on press conferences with President Reagan guys on the side with VERY long directional microphones. They had them mounted on their shoulders and they seemed to be taking the questions.

The rumour mill over here said that they were called bazooka mics and they were made by RCA. Any truth? I suppose they didn't work out as I've not seen them since.

[Grayson L. Wideman]

Did they seem to be pretty much a bunch of tubes? If so I'm sure that they led to the development of the line gradient shotgun mikes we know and love.


Grayson

[Nick Flowers]

Aha! Yes I remember seeing pictures of these mics, looking rather like a semi-sawn off Gatling gun. Made by Westinghouse or Western Electric? Each tube was the equivalent of one of the slits in an interference tube, I think. But not what I had in mind. On going research has discredited the RCA theory and EV is now a contender. The quest continues.

[Giroud Francois]

http://www.amazing1.com/accoustics.htm

[Nick Flowers]

How interesting! Thanks for that link, Giroud. That build it yourself 30 tube mic that can 'pick out whispers in a crowd' and 'hear through windows' would seem to be just what we need today! Perhaps a little hyperbole is being used here. But no doubt this is just the principle upon which those mysterious microphones I saw all those years ago worked. I was also interested to see all those parabolic mics being advertised. I read a very long article about them in an old BBC book. Oddly enough placing the mic at the focus of the parabola was not recommended, as you traded loss of directivity for improved flatness of frequency response if you went just a little bit past the focus. BBC used them to pick up the 'thwack' of willow on leather at cricket matches. In the same book a huge 'microphone', hundreds of feet long, was described, used to measure atmospheric effects.

[Ty Ford]

Gents (and ladies),

Pretty much, if the laws of physics allowed a bazooka mic that provided acceptable results, the mic makers would have it on the market.

Despite what we see in the movies and on TV, some of that technology isn't here yet and/or may never be.

The spooks may have (well they do have) some gear that pushes the limits of physics, but there's hefty DSP and the audio is for surveillance, not for sounding anywhere near good enough for your next wedding or corporate/industrial shoot.

Regards,

Ty Ford

[Sacha Rosen]

Just imagine, Huge floating bazooka mics in orbit around the earth... Then imagine the Rycote!

[Sacha Rosen]

Of course I don't think there is much wind in space.

[Nick Flowers]

Yes, the laws of physics are immutable...and yet I remember reading in another thread on this forum that sometimes it is possible to get rid of reverb, to a degree. That's something that we all thought utterly impossible 10 years ago. (To be honest I still thought that it was impossible until I read the posting). If you'd told the VT boys 20 years ago that their 2" tape quad head VTRs would be surpassed by something on the back of a camera, they would have told you that THAT was against the laws of physics.

But actually that isn't my point! I'm just curious to find out what these wretched bazooka mics were, who made them and just how did they perform. Mind you, the exaggerated estimation of the public about the capabilities of directional mikes can be exploited: it does put the jitters up a group of cops if you point an 816 at them and and nod and grin.

[Giroud Francois]

parabolic mic are not very directional, they just give some boost to weak signal.
of course they are directional but not as much as shotgun mics.
shotgun mics are based on 2 principle.
one is to set 2 mics in a tube and use one to substract the signal from the other, so you get the directional effect. (this is first order system, second order could use a third mic)
the other type is using slots on a tube so aligned sound waves are reinforced while misaligned are weakened.
the same principle used for planar array of mics.

the huge mic tube sold on the link above is the last type (slotted tube).
the diameter of the tube just increase sensitivity and performance at low frequencies, so it is not silly design.
The fact you do not find them easily on the market doe not means it is useless, just that nobody would carry such microphone in regular condition.
i got a huge parabolic dish (80 inches diam) and putting a mic on it gives great result.

[Nick Flowers]

So presumably the type of directional mic mentioned by Grayson (above) which consisted of a bunch of tubes of different length would be a fore runner of what we have now (interference tube) rather than two or more mics in one unit, as you mentioned, Giroud?

[Giroud Francois]

it seems it could be some kind of planar array mic , perhaps enhanced with tubes.
could be a very strange design but with very high performance.
But surely not something you would carry in your camera bag everyday.

[Ty Ford]

and requiring a lot of DSP to correct the phase issues that multiple diaphragms creates.

Audio Technica used that approach in the AT895 for noise canceling mic.

Audio-Technica - Microphones, headphones, wireless microphone systems, noise-cancelling headphones & more : AT895 Adaptive-array Microphone System (DISCONTINUED)

How much reach does the market need? Can a mic be designed that provides exceptional clarity and frequency response at 40 feet? Oh, and make it no heavier than 12 ounces.

Maybe, but a mic maker needs to be able to recoup R&D and manufacturing costs. They need to sell enough of them to do that. Low volume specialty gear has always cost more because the profit on the return simply isn't there.

Spooks at NSA spend a lot per piece for surveillance gear, but the audio quality is a trade off for other performance features.

Regards,

Ty Ford

[Paul R Johnson]

The performance of dishes is much better than line-gradient type shotgun/rifle.

The Big Ears, which is a fairly small dish used on sports events has this spec:
Technical Specification:
Big Ears Little Ears
Overall size: 675 x650 x250mm 405 x380 x140mm
Parabola size: 585mm 330mm
Weight: 3.3kg 0.9kg
Working range: 100–15000Hz (note 1) 60–12500Hz (note 1)
Pick-up pattern: 800mm diameter target at 600mm diameter target at
30 metres (tunable) 30 metres (tunable)
Useful range: 1.5 metres to 90+ metres 2 metres to 90+metres

Note 1: Dependent on microphone
Note 2: Dependent on environment and surrounding noise level


That's a very narrow beam - much narrower than a normal shotgun/rifle

[Ty Ford]

Not doubting you Paul, but my experience with dishes is that the fidelity isn't all that good. (but good enough for getting the quarterback's shout and bodies crunching together.)

Regardless, not something you'd want to use for dialog in a movie.

Regards,

Ty Ford