Rotary Subwoofer? Eminent Technology TRW-17

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Rotary Subwoofer? Eminent Technology TRW-17

Postby EWBrown » Tue Apr 13, 2010 6:13 pm

I was initially undecided whether to post this under the "speakers" or the "advanced snake oil" topic.

Eminent Technology TRW-17 Rotary Subwoofer

http://www.rotarywoofer.com/

And, "How it works" http://www.rotarywoofer.com/howitworks.htm

A subwoofer without a cone. Essentially, it consists of large fan, which is equipped with a variable-pitch propellor, the pitch being controlled in amplitude, and direction, by a voice coil mechanism.

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An interesting, if not entirely practical, method of generating very low frequency, powerful sound waves.

/ed b
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Postby battradio » Wed Apr 14, 2010 3:40 am

I would hate to hear it after the bearing started to wear out .

Don't think it would be pactical in a home seting , but in a football stadium for a high school it might put out some nice boom boom boom .
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Postby EWBrown » Wed Apr 14, 2010 7:41 am

One of the guys over at NNETG (Ed Sawyer) has personally witnessed this device, here are his comments

I've seen/heard this woofer in action, at a show. It was insane. They had to
have a whole floor of the hotel to themselves, since the bass was so immense.
Just absolutely clean, pants-flapping bass down to basically sub-audible levels.
The enclosure was fairly large (think large closet-sized), but could have been smaller.

The blades move the same way helicopter blades move, its' impressively
simple yet also complex enough that DIY'ing it would be challenging.

I talked at length with the designer about it, there were some tradeoffs
(fan speed vs. response, etc.) but all in all, it was an amazing item.
Sadly, priced out of reach for me at the time. Haven't revisited the idea
since but it's a worthy system.

-Ed


Just imagine horn-loading it 8^0

/ed B
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Postby Geek » Wed Apr 14, 2010 9:52 pm

They used one on Mythbusters :-)

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Postby Ty_Bower » Wed Apr 14, 2010 10:07 pm

Sadly, priced out of reach for me


Just how far out of reach are these things priced? I think I might like the idea of something that'll chase the rodents off the whole floor of the hotel.
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Postby EWBrown » Thu Apr 15, 2010 7:49 am

As I recall, "Mythbusters" also created a mechanical "subwoofer" in an old Mercedes-Benz. It had an approximately four foot diameter cone, and it was "pumped" by means of a cam or crankshaft mounted on the car's driveshaft. It was mounted facing upwards in the back seat area.

It ended up tearing itself apart before it could cause any "acoustic damage".

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Postby Geek » Thu Apr 15, 2010 2:45 pm

EWBrown wrote:As I recall, "Mythbusters" also created a mechanical "subwoofer" in an old Mercedes-Benz. It had an approximately four foot diameter cone, and it was "pumped" by means of a cam or crankshaft mounted on the car's driveshaft. It was mounted facing upwards in the back seat area.

It ended up tearing itself apart before it could cause any "acoustic damage".

/ed B


The episode I was thinking of was the one they were subjecting the plant to all sorts of torture in the box.... or was it Grant? XD

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Postby Shannon Parks » Sat Apr 17, 2010 6:25 am

Perfect for the home theater - particularly in the summer time! :)

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Postby EWBrown » Sat Apr 17, 2010 6:06 pm

From the continuing discussion on NNETG, apparently this system can produce sound waves as low as 2 Hz at full output. Feel it, as well as hear it...

The blade pitch control is similar to that used on a helicopter's "cyclic" control.

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Postby mesherm » Sat Apr 24, 2010 11:58 pm

The blade pitch control is similar to that used on a helicopter's "cyclic" control.

As an owner of an RC heli the subwoofer blade pitch control is actually duplicating the action of the "collective" stick in that it changes all the blade's pitch by the same amount. The "cyclic" changes the pitch as the blades reach a particular angle in their rotation. What angle you move the cyclic stick determines where in the rotation the pitch changes.
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Postby EWBrown » Sun Apr 25, 2010 1:50 pm

Collective would be correct, I had my collective cyclics confused...

Similarly, the old propellor passenger planes had variable pitch props, and these were thrown in reverse after landing, in order to slow the aircraft down, as the LG brakes weren't designed nor capable of performing this on theor own. I just hope that there was an idiot-proofing scheme in place, so that the props couldn't be reversed while in flight. That could truly be a real "let-down"...

/ed B dephiniteively NOT a helo-pilot, either real or R/C
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