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Post by ThomasW on Sept 30, 2005 20:38:42 GMT -7
I had occasion to attend a demo of Bruce Thigpen's Rotary IB subwoofer at the RMAF-2005 today. This is an amazing device. Here's a picture of one of the prototype drivers.  Here's a LINK to a webpage where I uploaded more pictures of the operational unit. He has a 'manifold' and everything ....  The upper frequency limit is 40Hz. The demo included 1Hz increments from 10Hz down to 2Hz. At that point the room was pressurized and the drywall was noticably flexing. His crew was also putting pressure on all the doors to keep them from rattling in their frames.....  |
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Post by formica on Sept 30, 2005 23:21:59 GMT -7
and it'll keep you cool on those hot summer days... ;D
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jonfo
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Post by jonfo on Oct 1, 2005 4:09:09 GMT -7
Very Interesting. See here for more info on the theory behind this device: www.eminent-tech.com/howitworks.htmwww.eminent-tech.com/main.htmlI can see how it might be effective at a a given frequency, but how does it sound when playing back complex tones, like music? The real trick is how would one integrate this with the cone IB at the 30Hz point? Or is this basically the IB part of the bass system, and cones in boxes would have to take care of the rest? While I'm not ready for a $12K driver just yet, I'd go for something like this at $5K to $8K. |
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Post by ThomasW on Oct 1, 2005 7:38:37 GMT -7
$12K is for a handmade unit. Bruce said the price will plummet when it's actually in 'production'.
It's to augment the output of exsiting subs in VERY high-end custom HT's, I imagine it will work with any type of cone sub
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jonfo
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Post by jonfo on Oct 1, 2005 10:08:25 GMT -7
Yep, I also expect the cost to drop when volume production starts. Here is a very interesting discussion of it back in June, Bruce T himself chimes in on this thread at AVSForum www.avsforum.com/avs-vb/showthread.php?t=550410&page=1&pp=30As my current IB can pressurize the room pretty well, I'm in no rush. But I am the kind of guy who would (will?) buy one of these to go even lower. The trick is, I already have one IB, so how would I integrate this as well? |
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Post by frantzm on Oct 1, 2005 10:16:39 GMT -7
Hi
I wonder if 8 AValanche 18-inchers in a properly built manifold would not match its output and provide lower distortion figures? They would cost less too, much, much less...
Frantz
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Post by ThomasW on Oct 1, 2005 10:43:06 GMT -7
Bruce said the distortion was less then that generated by one dozen 18"s playing the same SPL. It's not supposed to replace standard subs. The device down goes down to DC (which is fairly "subsonic" ). So the idea is to augment the output from existing subs for those people who have the $$$$ and a place to put the subwoofer. |
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Post by mannthey on Oct 1, 2005 12:18:17 GMT -7
"In order to hear 10Hz you need sound pressure levels above 100dB. To hear 5Hz you need sound levels above 110dB." --from their website. This whole thing sounds sort of unnatural (how much infomation is encoded in dvd's and music in this 1=15hz range @100db and above?). This sub might be capable but is there any informtion you are ment to hear? I can only imagin how much damage this would do to your house and listening area. Rattle what rattle?  Thanks for pointing this out. I have never seen anything like it before. |
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Post by formica on Oct 1, 2005 23:46:50 GMT -7
All joking aside, it great to see designers thinking outside the box. Without a doubt this is different and looks logical... Right off the bat, it seems more practical that those "ultra" high excursion woofers demo'ed by adire and the like.
I'm not yet convinced it'll have less distortion than a dozen 18" (those would be loafing along at those SPL)... as the blades do have the risk of aerodynamic noise at higher volume displacement. I'm curious to see how it actually tests...
Tech has been stagnant too long... these are the most innovative things I've seen since the contrabass...
Rob
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Post by ThomasW on Oct 1, 2005 23:53:40 GMT -7
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ken
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Post by ken on Oct 2, 2005 2:33:32 GMT -7
Hey Thomas. as you were there what was your impression of this subwoofer while operating?......l know it's limited as to bandwidth but did it give a .......for want of a better word.........deeper more full experience than we'd get of a regular ib?..just curious what you thought.......cheers Ken
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Post by ThomasW on Oct 2, 2005 7:52:37 GMT -7
I was literally slack-jawed at it's performance. Like our IB's, it didn't blow you down with sound. The sensation was that the low frequencies were just 'appearing' in the room. With SPLs loud enough to flex the drywall, one could still carry on a conversation. Sound quality seemed very good, difficult to tell with only test tones. When I win the lottery buying one will be priority .......  |
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Post by jman on Oct 2, 2005 12:58:30 GMT -7
If they went into large production, could the price fall to the $1500-2000 range? If it did, would one run this from 0-20hz and then let the subwoofer do 20-80hz? I've only tried the Crowson tactile transducer, the effect was neat but somewhat distracting/disconnected from the rest of the sound, maybe this is the right way to fill in the first few octaves. Imagine the Irene scene from BHD on this thing.
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Post by ThomasW on Oct 2, 2005 16:22:44 GMT -7
The target buyer is high-end HT owners. My guess is ~$5000 for the first production units. After a few years in production the cost would certainly go lower.
I think your integration idea is on target.
This device has the potential to put serious stress on the structure. Anyone considering it should take that into consideration.
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jonfo
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Post by jonfo on Oct 2, 2005 17:46:17 GMT -7
The target buyer is high-end HT owners. My guess is ~$5000 for the first production units. After a few years in production the cost would certainly go lower. I think your integration idea is on target. This device has the potential to put serious stress on the structure. Anyone considering it should take that into consideration. Well, I'm the target then I did build my house around the theater (no Kidding, it was design element #1). And it's really, I mean really solid. Even after a year of IB pounding, no rattles (other than stuff in other rooms ;D ) |
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Post by ThomasW on Oct 2, 2005 18:26:13 GMT -7
Then you better buy two... |
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Post by JeremyG on Oct 3, 2005 13:24:04 GMT -7
I'm interested in how the thing works. I work on airplanes with propellers and helicopters with rotor blades. I would think that due to the fact that the inside of each arm/fan/blade is spinning at a slower rate than the outside, there'd be harmonic issues. I guess it would depend on at what rpm it is spinning. Also the flexing and rigidity would be an issue with each arm/fan/blade as it pivots. Or maybe I'm just used to fans that are 6 to 48 feet in diameter. Does anyone have a link to an answer or just know? I'm not in the market, but it's just such a cool idea I'd like to know more.
Jeremy
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Post by JeremyG on Oct 3, 2005 13:33:31 GMT -7
Nevermind, I answered my own question.
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Post by Michael Mitten on Oct 3, 2005 13:44:07 GMT -7
My question is how in the world did someone one come up with this idea?!
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Post by ThomasW on Oct 3, 2005 16:37:14 GMT -7
If you've been around audio a while you'll be familar with Bruce Thigpen, (think air-bearing tone arm), and know he's one smart cookie ..... He said he was thinking about the cone/air interface of a conventional driver at low frequencies and what to do about that problem. This is what he came up with...... Note that there have been other 'rotary' drivers (Tom Danley created one). Bruce's is the first to work in this maner (varying the pitch of rotating group of blades according to frequency) . |
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