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[Magnus "Magic" Johansson]

 http://www.sonicflare.com/archives/eminent-tech-trw-17-the-m ost-powerful-subwoofer-in-the-world.php

And cheap too, only 12900 $

I'm sorry, couldn't resist !

[Michael_Elliston¶]

Not necessarily the most powerful,but definately goes LOW.

Is 3hz necessary one might think - Already HT heads are deafening themselves with exxagerated unnatural 20hz...

The only time I get bass in real life is from trucks,trains etc.

Probably a multiple 15" IB will do almost aswell to 10hz while saving some money for the piggybank.

[[x]]

I think this is the most impractical thing I have probably ever seen, and it has been posted over and over again to every audio forum I have visited in the last week. This is getting annoying, like that Royal Device "world's largest folded horn" in the floor of some guy's specially-built listening room that everybody seems to feel the need to alert us to. This is insane and needs to stop.

Yes, we have all heard and read about the Eminent Tech 'fan subwoofer'. Some justification for why it is impractical: Hugely inefficient (the motor runs and draws power even when the blades are not pitched), no baffle (adding to the huge inefficiency by an inability to create a large pressure differential in a big room), and mechanical noise (motor bearings, linkages, propeller rotation).

[John Halliburton]

I'm not going to say it...I'm not going to say it...  

John

[[x]]

a Tom Danley creation? (In reference to the 3Hz horn)

[Tim Duffin]

How about the fact that it can't possibly be very loud when compared to any speaker that isolates the front wave from the rear wave.  I could see this being very novel until the air in the room just starts loading the fan blades and you get very little increase in volume-- Heck, ill build one of those in my garage tomorrow and save you 12 grand, Ill let you know how it sounds.

T

[John Halliburton]

From a project originally for Georgia Tech, for sonic boom simulations, circa '91 or so.  They parked the system next to a test house with subjects inside.
Tom could certainly give a better account of the history and the design, although the "loudspeaker" in the photo was half of the bottom end of the system-one more unit like the one pictured, then there were four Basstech 7 cabinets and then some 15" and some 2" horns.

Best regards,

John

[Michael_Elliston¶]

John Halliburton wrote on Sun, 06 November 2005 17:59

From a project originally for Georgia Tech, for sonic boom simulations, circa '91 or so.  They parked the system next to a test house with subjects inside. Tom could certainly give a better account of the history and the design, although the "loudspeaker" in the photo was half of the bottom end of the system-one more unit like the one pictured, then there were four Basstech 7 cabinets and then some 15" and some 2" horns. Best regards, John

I remember him saying something about this thing,testing it in a driveway. Whats the design idea? Obviously not a regular basshorn but some kind of resonant thingimijig

[Graeme Goodacre [Centauri]

US Patent 5140641

Cheers
Graeme

Edit: worked out how to format URL ......

[Phillip_Graham]

John Halliburton wrote on Sat, 05 November 2005 23:59

From a project originally for Georgia Tech, for sonic boom simulations, circa '91 or so.  They parked the system next to a test house with subjects inside. Tom could certainly give a better account of the history and the design, although the "loudspeaker" in the photo was half of the bottom end of the system-one more unit like the one pictured, then there were four Basstech 7 cabinets and then some 15" and some 2" horns. Best regards, John

Hey John,

For what it is worth, there a still a couple of BT7s parked on a shelf at the end of the high bay in the MARC building here at Georgia Tech.  I can't help but wonder if they are part of the remnant of that system.

I remember seeing it featured on the show Beyond 2000, and that the large horns had a rotationally oscillating vane "driver"  Really testing my memory I think they were painted red.  Funny to think I walk by what might be left of that several times a week...

[Antone Atmarama Bajor]

      I've heard that eminent tech is looking into making the fan sub portable and more cost effective, they are selling mostly one offs at the moment.

    I'm sure a good industrial motor will suck a little juice but need minimal maintenance.  But I'd be more concerned about how much noise the thing makes at idle.

    I don't think there is anything comparably efficient in those ranges that uses conventional voice coil/loudspeaker technology (Though Threshold of hearing becomes an issue).

    For what it is I don't think it warrants the price they are asking other than to pay for RnD.  But I think its a very smart Idea that should be explored further.  If it can be made portable and more efficient, then it could be a contender in many different markets.  Isn't it time for HI-FI HVAC.

    I don't think anyone should diss it or doubt it potential.  Isn't it all about modulating air pressure!?.

Antone-    

[Michael_Elliston¶]

Quote:

The sources were a “flow modulator”, what I would call a class A valve in that it is half open at “no signal”. A voice coil motor moved the valve, either opening further or closing off the valve relative to the no signal condition. The sources on the towers were made by LTV-Ling, the former industrial branch of Altec Lansing and now a defense contractor. I could not find my data sheets or the exact unit on line but I did find a similar source made by Wyle Labs. http://www.wylelabs.com/sp1b.html At the time, Wyle Labs (who were located kind of across the highway from MSFC and Redstone arsenal) did all the vibration testing on our payloads. They also had the largest tube amplifier I have ever seen, it was something like 250KW, it had two huge output tubes and BIG driver tubes, water cooled and took up an entire wall in a good sized room. This drove the shaker tables and as one fellow described, with a sheets of plywood attached to make a “radiator” and moved down its track to the dock door, did a fair job broadcasting Christmas carols. Anyway, the “down side” of these flow modulators was the noise from the ~ 30 psi air flow (supplied by a big diesel air compressor ) limited the signal to noise ratio (the sound it makes with no signal compared to the sound it makes at max drive level) to only about 10 dB. This was the problem I faced when designing the sonic boom simulator for GTRI. They needed a source to study the acoustic signature of the space plane NASA was working on, given its large size, the sonic boom was going to be a doozey. An “N” shaped wave with a 3 Hz period. This simulator system needed to produce 132 dB from 5 kHz, down to 3 HZ, outdoors, 2 meters from the wall of an old house next to the air base outside Atlanta. This output required the equivalent displacement of a piston 12 feet wide and 8 feet high, moving 18inches peak to peak at 3 Hz. My solution was to use a “push pull” valve and lower the pressure to about ¼ psi. Given the job it had to do, it required an air source moving about 50 cu mtrs per second and this required a special 3 phase service to be run to the site for the 12, 5HP fans. This flow modulator had vastly more air flow volume and a much lower pressure, combined with the class”A” push pull valve, increased the signal to noise by about 100 (20 dB) compared to the high pressure versions. For such a valve to be used in the home which is a contained space, it is worth considering that an air pressure of only 1/100 PSI is 132 dB SPL or 1.6 pounds per square foot applied to your walls ceiling and floors. At the old house in Atlanta, with 132 dB available (on one wall) and using a slow sine sweep with the TEF machine, I was able to find the fundamental resonance of the test wall. In the middle where the window was, the pressure could move it in and out about a foot and a half peak to peak at 4.5 Hz. No one of our group was able to stay in the house during this (in fear) and later when a loud CRUNCH came from somewhere below the floor, we stopped teasing the old house. I’ll never forget the feeling of standing between the house and the system with the “pickle” button that made the “N” signal. It was the kind of KAAABOOM, very satisfying to do in rapid succession until you saturate and have to get away. The actual use of the system the customer had in mind involved observing dishes and household stuff as well as test subjects when it went off with no warning. Best Regards, Tom Danley Danley Sound Labs

http://db.audioasylum.com/cgi/m.mpl?forum=hug&n=92422&am p;highlight=drive+way+Tomservo&r=&session=

[Michael_Elliston¶]

I wonder how much it would cost to buy the blower and servomotor -Just have to try it sometime!
There must be some equations to size the circulating 'tunnel' and ports?
Just wondering how physically large this thing is - 1700L or larger?
Mike.e

[John Halliburton]

In that photo I posted, the center cabinet is 1600mm x 1600mm x 60mm, and the flares are 1800mm long, with a mouth that is the same 1600mm square as the center cabinet(metric approximations done before my first cup of coffee is finished, so margin of error could be huge)

Have fun!

Best regards,

John

[Marcel Groen]

Hi,

I looked over the patent and i see that this is a really simple concept. Just blow enough air to the vane, the vane claps air to the outside off the box.

At the moment i am also trying to build i servodriven subwoofer(something like the contrabass), already bought several dc servomotors. The downside of the diy-er is that the construction of such loudspeaker is a not an easy task, especially with the belts.

This construction is much easier. Do you know if the rotary vane subwoofer is suitible for pa-use and if a high cut-off to
90/100hz could be reach? It looks to me that this is impossible. What is a typical speed of air when passing the vane in his no-signal position?

Marcel

[Craig Leerman]

Tp participate here, you need to use both First and last names as your handle.

thanks
Craig Leerman
Forum Moderator

[Tom Danley]

Hey John


I have another shot of 2 or the 6 production units.
Notice your Baltic birch TEF cart is in the foreground.
That’s all it took to make the TEF-10 plus the Delta Omega amp and tractor printer a “portable” measurement system, Pretty cool at the time.
In the background it looks like a bunch of Disney “cheese burgers” and on the top shelf, it looks like a TPL-2 or 3 module with one of those Community 4X12 speakers (shop pa) below.  
Getin down right nostalgic, didn’t have Grey hair back then either.
Best,

Tom Danley

[Tom Danley]

Hi Micheal

Here is a view of the output end of the entire system.
Standing between this end and the house 6 feet away was my preferred  “listening position” for the recreational the sonic boom “listening tests” with the pickle I wrote about.
Actually it was pretty intense and wore you out after probably 10 or 12 rapid succession booms.
One of our Guys, Jim Rix listened to music through the system (loud) a number of times but I found it to be too distracting to do anything useful while it was on.
Being on a frontage road next to an airforce runway, making noise wasn’t a problem however.
Cheers,

Tom Danley

[John Halliburton]

And to think that style of computer case for the TEF 10 was called a "portable".  Aiiiieee!
It looks like the Basstech 7 subs to right and slightly behind are part of the bunch that went with the 3hz ultrasubs.

That's some loud stuff there.

John

[Michael_Elliston¶]

Thanks for the input Tom,seeing the pictures of the real life units are so much better than a patent diagram!

[[x]]

So when you played music through the whole system, how did it feel to have the most low end headroom of any system ever?

[Kit Hannah]

If I decide to get in on this technology, I'll make sure the frame of my house is welded steel. I thought I saw someone advertising this as an ultrasonic nail gun... and being in California, I would rather not have something in my basement or attic that basically simulates yet another earthquake!

The car idea is crazy too... I already hear enough trunks rattling like hell. But I guess if they do make it for a car, I can just tune in to the same station they are listening to while stopped at the light, lean my seat back, put my right hand on the top of the steering wheel, and act like it's coming from my ride.

[Peter Wing]

Just to make it clear, this rotary sub, works with a baffle, like an IB so VB is the adjacent room, or attic or whatever. Power consumption is 200w @8ohm. I believe it was originally known as the Thigpen Rotary Subwoofer. http://www.youtube.com/watch?v=E7Bkrypxzs4