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The Boffle

kfa888

kfa888

Addicted Member
Ever heard of this? Does anyone use this design. Seems odd.

The Boffle (a cross between box and baffle) was the world's first attempt at acoustically eliminating the driver's rear wave. The inside was a series of panels with acoustic materials stretched over frames that had descending and ascending center holes.

about a third of the way down this page...

http://www.soundfountain.com/amb/activsys1.html
 
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Kind of. Back when I worked for the Army Corps of Engineers doing acoustic R&D stuff we built a silencer for a tank. Sounds like a bizarre project, and it was. The thing was a large steel cylinder with baffles inside similar to the boffle. It was on a hydraulic lift that could tilt. It could be aimed at the approximate angle of the shot, then the tank was pulled up with the cannon pointing through the cylinder, the cylinder was filled with runway foam, and then you shoot. It was good for about 32dB of attenuation and you ended up with foam over about an acre.

Anyway, the boffle concept worked well for that.
 
RayW said:
Kind of. Back when I worked for the Army Corps of Engineers doing acoustic R&D stuff we built a silencer for a tank. Sounds like a bizarre project, and it was. The thing was a large steel cylinder with baffles inside similar to the boffle. It was on a hydraulic lift that could tilt. It could be aimed at the approximate angle of the shot, then the tank was pulled up with the cannon pointing through the cylinder, the cylinder was filled with runway foam, and then you shoot. It was good for about 32dB of attenuation and you ended up with foam over about an acre.

Anyway, the boffle concept worked well for that.
Click to expand...

Sounds like something Oddball would have equipped his Shermans with in Kelly's Heroes. "They never hear us coming. Scares the hell out of people. A Boffle can give you a very nice...edge." :thmbsp:
 
What a fascinating thread. I've filed away all the link url's and downloads from the links. As I work on my Bozak Urbans I've been wondering about how the cabinets could be made to exhibit the benefits of an open backed speaker without also exhibiting the disadvantages (the urban cabinets being a little too small and under-braced for the true infinite baffle designed bass drivers they contain). The boffle could well provide the answer. Thanks to you all for your posts.
 
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RayW said:
Kind of. Back when I worked for the Army Corps of Engineers doing acoustic R&D stuff we built a silencer for a tank. Sounds like a bizarre project, and it was. The thing was a large steel cylinder with baffles inside similar to the boffle. It was on a hydraulic lift that could tilt. It could be aimed at the approximate angle of the shot, then the tank was pulled up with the cannon pointing through the cylinder, the cylinder was filled with runway foam, and then you shoot. It was good for about 32dB of attenuation and you ended up with foam over about an acre.

Anyway, the boffle concept worked well for that.
Click to expand...

In a previous life I had a 55 Gallon Drum lined with fiberglass and chicken wire as a firing point in my basement. You stuck the muzzle in there and aimed for the sewer cover set at a 45 degree angle in a sandbox at 25 feet.

Mostly it provided good cover for ricochets, but the cops never got called.
 
Wasn't that the Nautilus (B&W) idea? ...to attenuate and absorb the rear wave?

Hey kfa888,

I read some of the stuff on that link. The part talking about the Janis subwoofer makes me kind of question the authors understanding of electronics. The blurb about torroidal transformers and filter caps makes me wonder.
 
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very interesting thread i have a pair of knight triaxles that i have been contemplating making better boxes for and this seems to be a good option, as it mention in the one article about using speakers with stiff accordion style surrounds are best for boffle style boxes which describes my knight triaxles, this would make a good winter project i think.
 
I guess it's a form of "lossy" system.

Maybe not the same, but sort of reminds me of a couple of Philips designs for 9710:

omnihorn.jpg

9710 box A5.jpg

They kinda are like giant plane-wave tubes, with that longitudinal glasswool wedge; in theory it should not even matter whether the end of the line is terminated or not as the rear wave should have been fully absorbed and transformed to heat at this point.

az
 
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