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Would you believe this is a subwoofer?

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Reverb

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Rocky Mountain Audio Fest

Held in Denver, Colorado, September 30 - October 2, 2005





The coolest product at the show was this Eminent Technology unit that produces 110 dB at 10 Hz. It is designed to supplement subwoofers (!!!) in the 5 Hz to 20 Hz range. A 1/3 horse power motor turns the fan blades, which are connected to a rod in the center of a woofer voice coil. Instead of the voice coil moving a cone, it moves the rod, which then moves smaller rods that adjust the pitch of the fan blades. So, the high velocity air coming from the fan is pulsed at the low frequencies. It only takes about 100 watts of amplifier power to drive it. The entire room shook, and the door was opening and closing in time with the signal. All this, and there was almost no distortion (the ET rep had the response being plotted on a spectrum analyzer during the demonstration). They calculated that it would take ten 18" subwoofers to produce this level of sound. It has to be placed in a separate room due to the fan noise, and putting it in the attic would work fine. The opening into your home theater would be about 2'x4' in the ceiling. These are prototypes at this point. All I know is I want one.


Source
http://www.hometheaterhifi.com/volu...ocky-mountain-audio-fest-10-2005-page-37.html
 

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Robin

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Me three!!!

Joe,

This could have a duel purpose in my HT, as it could help circulate the air, and in so doing, help cool down my HT room. :D

I looks so simple... Does it have any other components or just what you have pictured?

-Robin
 

SteveInNC

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I always like it when people try radically different approaches; the helium plasma flame speaker comes to mind, and of course we are using speakers made of fancy celophane powered by static electricity :)

I do have some questions about some of the article's claims though.

For example, the blade pitch coil may only take 100 watts to drive, but the fan motor looks to be about 2+ HP, which at 100% efficiency is 746 watts/HP. So, call it 2Kwatts to drive the fan motor. The general design of the unit mimics the collective pitch control on a helicopter, so the basic technology is well known. Ideally, they would have some sort of feedback to maintain RPMs as the blade pitch increases drag.

To have "almost no distortion" would imply that the blades are extremely rigid. As the pitch rolls on, the blades would be likely to flex towards the ends, meaning that the pressure wave would blur, starting at the hub and working out. This also assumes no distortion from blade vortices in the air, etc.

The article states that the effective power mimics that of 10 18" subs. Given the approximate diameter of the fan of 1 meter (guestimate based on room scale), that works out to around 0.8 sq meter surface area. Excursion as such is a maximum of one blade width. Since exceeding 45 degrees pitch will reduce the "push" of the air column, excursion is actually a bit less.

18" is about 0.5 meters, so a surface area of about 0.2 square meters X 10 units = 2.0 square meters. For the above correlation to hold, the fan unit would have to have an effective excursion of twice that of one of the sub cones. Could be possible. This is complicated somewhat by the blades only covering a fractional arc of the effective disk of the fan rotation, so the full column of air isn't simultaneously pushed. There is a lag proportional to the inverse of the rotation speed.

They could improve the efficiency of the design by A) making it a ducted fan, and B) using something approaching a many-bladed turbine layout so more of the effective disk is used to simultaneously push air.

I'd love to hear this thing in person.
 

Peter Hogan

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Taking this idea one step further, you could modify the inlet turbine of a jet engine, and REALLY get some serious output...:) The background noise of the jet might be a drawback though...

J/K,
Peter
 

kach22i

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I need one on my hovercraft, just not noisy enough yet. :D
 
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sakhavi

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SteveInNC said:
18" is about 0.5 meters, so a surface area of about 0.2 square meters X 10 units = 2.0 square meters. For the above correlation to hold, the fan unit would have to have an effective excursion of twice that of one of the sub cones. Could be possible. This is complicated somewhat by the blades only covering a fractional arc of the effective disk of the fan rotation, so the full column of air isn't simultaneously pushed. There is a lag proportional to the inverse of the rotation speed.
Steve, I don't know what you just said, but it was beautiful, man. :)

I'm just glad superior minds like yours are on our side.
 

MarkNewbie

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SteveInNC said:
I always like it when people try radically different approaches; the helium plasma flame speaker comes to mind, and of course we are using speakers made of fancy celophane powered by static electricity :)QUOTE]


Steve - You had me at "I".....LOL ;) See if you can understand this jargon.

Dude ! You ROCK!!

:cool:
 

Robin

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In laymen's terms.... What did you say?

Steve,

In easy to understand terms..., what did you say? :confused:

I just want to know, will this subwooter kick some serious butt, at low level db's? :D

Please get back to me...

Cheers

-Robin
 

SteveInNC

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Well damn... (blushing). Sorry, I'm always interested in the technical details of how stuff like this works, and try to figure it out. It comes from dismantling my toys when I was young. Sometimes, they even worked again when I put them back together :)

Roughly, the idea looks neat. I suspect it's not quite as distortionless as they indicate, because the fan blades won't move a column of air all at once the way that a standard cone driver would. I bet that their demo test signal was low frequency sine waves, which would be the easiest for this design to track.

Plasma speakers use ionized gas to make sound, sort of the way that MLs use the charge on the stator panel to move it:

The original Hill Plasmatronic speaker (in German, but has pictures):
http://www.plasmatweeter.de/plasmatronic.htm

Build your own!
http://www.plasmatweeter.de/eng_plasma.htm


Re: jet engines, you could roast marshmellows too while you listen :)

My idea is to have a sub based on a series of explosive charges. You have to reload it each time you listen to a tune, but the 1812 Overture would be magnificent.
 

Robin

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SteveInNC said:
Re: jet engines, you could roast marshmellows too while you listen :)

My idea is to have a sub based on a series of explosive charges. You have to reload it each time you listen to a tune, but the 1812 Overture would be magnificent.
Sounds like a fun, all-be-it, hot / explosive, listening experience... ;) Rollicking good times all around, just some good, dynamic, audio fun... That is, if the house remains standing at the end of the, "1812 Overture"... :D

Thanks for the quick and witty, 'user friendly', reply, Steve... :D

Cheers

-Robin
 
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BearcatSandor

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Yanno, I'm not a speaker builder, but i bet this wouldn't be too hard to build.
 
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BearcatSandor

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The appearance of the cooling device...er...um...subwoofer is different on the companies page then what's posted above:

http://www.eminent-tech.com/main.html

All I know its that with one of these and a set of Summits i'd be all happy as the full range would be covered and then some!

Also note that this company makes electrostatic speakers that have gotten good reviews and appear to have the same frequency responce for a lot less then the Summits. I'd be willing to bet that the Summits sound better though, given the R&D that Martin has put into their speakers.
 

MarkNewbie

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BearcatSandor said:
The appearance of the cooling device...er...um...subwoofer is different on the companies page then what's posted above:

http://www.eminent-tech.com/main.html

All I know its that with one of these and a set of Summits i'd be all happy as the full range would be covered and then some!

Also note that this company makes electrostatic speakers that have gotten good reviews and appear to have the same frequency responce for a lot less then the Summits. I'd be willing to bet that the Summits sound better though, given the R&D that Martin has put into their speakers.
Neat website. Thanks for sharing.
 

SteveInNC

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Looking at the response graph on their website, note that the fan system response curve falls off 10db from 10hz-30hz, and then continues to fall off as you move up the scale. They still don't give any information as to what test signals that they used, meaning that transient response could really suck. No THD listed. I'd still like to hear one though, just to see how it sounds.

I also note that by comparing their unit to a boom box car system they may give clues as to the fidelity and customer base that they're targeting: "volume at all costs". Show me the response against a Depth or an SMS in a real listening environment, not in a Honda Accord.
 

MarkNewbie

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SteveInNC said:
I also note that by comparing their unit to a boom box car system they may give clues as to the fidelity and customer base that they're targeting: "volume at all costs". Show me the response against a Depth or an SMS in a real listening environment, not in a Honda Accord.
I would guess that not many in that "target group" could afford the price tag though. :eek:
 
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