There is a very recent thread on this one (fan sub). And it is indeed capable of producing any frequency and amplitude within its working range.
The pitch of the blades are controlled by the audio signal while the fan is turning at a constant speed.
AFAIK such devices were tested as weapons in the late seventies/early eighties - capable of generating 10 kW of acoustic power below 10 Hz.
Regards
Charles
The pitch of the blades are controlled by the audio signal while the fan is turning at a constant speed.
AFAIK such devices were tested as weapons in the late seventies/early eighties - capable of generating 10 kW of acoustic power below 10 Hz.
Regards
Charles
Let's get real.... of the hundreds of people that heard the demo, no one was injured or killed. Or if they were, Bruce did a hell of a job of hiding the evidence ..... 😀
With this thread I know of 2 people that had vestibular issues. The same thing would occur were they listening to a massive standard sub reproducing the same frequencies
Also it's not designed to be used as a weapon. It's 'range' is SEVERELY limited by the design.
With this thread I know of 2 people that had vestibular issues. The same thing would occur were they listening to a massive standard sub reproducing the same frequencies
Also it's not designed to be used as a weapon. It's 'range' is SEVERELY limited by the design.
weapons grade sub
Well, the builder/engineer of the unit said to let him know if anyone got nausious so he could shut it off, and he advised folks to sit down so as to not fall over. I either couldn't hear, or rather did not want to listen to anything I heard elswhere at the show for a couple of hours. Just one man's journey. A personal experience.
As a home builder, I certainly would not install the device anywhere the structure was merely built to code. Nor would manufaturers of windows, doors, siding, trusses, joists, etc. be expected to honor their warranties in such an environment. The structural integrity of the facility can not simply be overlooked, as evidenced by the walls of the hotel room visibly waffling an inch or more (?) each direction. How long do you have operate this thing until nails begin pulling out? The stress will begin to take its toll on the materials the home or "enclosure" was built with.
Both the human and structural physical effects should be well considered before subjecting yourself, your family and your home to this type of device. I wouldn't want my pregnant wife or children anywhere near this thing. If my neighbor had one I'd lobby for its removal. The liability is massive, but hey, as long as the theater sounds great!
Wouln't it be a kick to see the UBC ammended for the sake of a LF device...
Well, the builder/engineer of the unit said to let him know if anyone got nausious so he could shut it off, and he advised folks to sit down so as to not fall over. I either couldn't hear, or rather did not want to listen to anything I heard elswhere at the show for a couple of hours. Just one man's journey. A personal experience.
As a home builder, I certainly would not install the device anywhere the structure was merely built to code. Nor would manufaturers of windows, doors, siding, trusses, joists, etc. be expected to honor their warranties in such an environment. The structural integrity of the facility can not simply be overlooked, as evidenced by the walls of the hotel room visibly waffling an inch or more (?) each direction. How long do you have operate this thing until nails begin pulling out? The stress will begin to take its toll on the materials the home or "enclosure" was built with.
Both the human and structural physical effects should be well considered before subjecting yourself, your family and your home to this type of device. I wouldn't want my pregnant wife or children anywhere near this thing. If my neighbor had one I'd lobby for its removal. The liability is massive, but hey, as long as the theater sounds great!
Wouln't it be a kick to see the UBC ammended for the sake of a LF device...
BTW...
A hem...Hundreds of people hearing the demo? Maybe, but it didn't look like ther were hundreds of people at the entire show, turnout was mediochre at best. I was there 3 days.
A hem...Hundreds of people hearing the demo? Maybe, but it didn't look like ther were hundreds of people at the entire show, turnout was mediochre at best. I was there 3 days.
i dont think it was very well advertised. i didnt even know it was there... and i knew like 50% of the people there personally, and no one told me about it. they had their own floor from what i hear, and i just never really made it there.
Re: weapons grade sub
you are quite the salesman, you are making me REALLY want to build one now! keep talking and im going to save up $13k!
(im a bass-head, i currently run dual velodyne DD-18;s and am thinking about adding tactile transducers too)
optichammer said:
you are quite the salesman, you are making me REALLY want to build one now! keep talking and im going to save up $13k!
(im a bass-head, i currently run dual velodyne DD-18;s and am thinking about adding tactile transducers too)
One of the people I was with touring the RMAF had a similar experience. He was okay after simply leaving the room. BUT it would be the same with any massive conventional sub reproducing the same frequencies. My big IB will do 5Hz and if I run test tones certain people have problems with it. My standard construction house however has no problems with frequencies that low.
The whole point of Bruce's presentation was as a "study" the signs clearly stated that.
Me too, and yes several hundred people heard Bruce's sub.
Obviously you're one of those "glass is 1/2 empty" kind of guys. Fortunately no one's going to put a gun to your head forcing you to buy one of Bruce' subs....
Rob,
Well it takes Boulderites a while to stabilize after leaving the cosmic center of the universe... 😉
If you don't know the basis for this joke email me and I'll explain it...
Also why don't you contact Bruce and become a dealer for their products?
hah, i got your comment about boulderites, but im not a boulderite. i live in erie and have for the past 2 years, so hah!
hum, why WOULD i want to be a dealer for bruce? what else does he offer? im always interested in signing up for a dealership, but if there is nothing they carry, why bother... if there is a reason i should, let me know and i will.
hum, why WOULD i want to be a dealer for bruce? what else does he offer? im always interested in signing up for a dealership, but if there is nothing they carry, why bother... if there is a reason i should, let me know and i will.
They're http://www.eminent-tech.com/, and may not have anything useful for you other than the rotary sub. Their hybrid planars don't get very good press.
Let me know if you come up with a good design for your own version of the rotary sub. If it's close to what I heard at the show I'll buy one to augment the bottom octaves of my big IB .... 😉
Let me know if you come up with a good design for your own version of the rotary sub. If it's close to what I heard at the show I'll buy one to augment the bottom octaves of my big IB .... 😉
ThomasW said:
yeah, i dont see anything worth selling. their "speakers" look like hell.
but, if you want a rotary subwoofer, im sure i could become a dealer and give you one heck of a deal 🙂
ive got too many other projects right now, but ill keep active on these threads and hopefully someone will come up with something. im sure if the RPM was increased significantly, and some minor tweaks were made, it could go up to 80hz or so... there is no reason it can ONLY do 1-30hz. and if it could do the whole frequency band, that would be a much cooler project.
ThomasW said:
interesting thought...
i wonder if there is a way to make the fan blades quieter?
i have an idea for a flexible fan blade. think of it like a flexible (pliable) piece of plastic. instead of simply turning or pivoting, it would twist internally. it would have a rod inside the fan blade and when it was twisted, the base of the fan blade would stay stationary, but the main body of the fan blade would flex and twist. it would be a bit more compelx to make, but in my mind, maybe it would have less flutter noise? just a random thought.
i think the key to this would be to figure out how to make the fan blades quieter. from 30hz to 90hz is only 1.5 octaves... so, getting it just 2 octaves higher makes it a much more viable product.
I think it's simply the blade motion itself that causes the flutter. Changing the mechanics of how the motion is created probably won't significantly change the amount of flutter.
I imagine a laminar flow blade shape would help with the issue. That of course means big time computer sims.
and what if you use fans like this:
An externally hosted image should be here but it was not working when we last tested it.
If fan noise is proportional to blade speed, and we want to maintain the same mechanical impedance, than the solution is to (like the above picture), increase the fan size and reduce the rotational speed. However, I believe there are design hurdles when increasing the fan size to compensate enough for fan noise. Perhaps at most it can be reduced.
In a quarterwave-tube this thing might be usable as an excellent neighbour-annoying device. 🙂 😀 
Regards
Charles
Regards
Charles
I'm gonna have a crack at making a ghetto one
I've cut apart an 6.5inch speaker that I accidently bent the basket on which should be good for atleast 100 w rms with a bit of venting. It also has a convenient hold running through the centre of perfect size.
Going to collect some fibreglass sheeting (similar to pcb fibreglass) to make the fan. Only thing I'm missing is a decent motor but I've got some remote control car one (rs540 I think) which will do for a test at low voltage
As a general quetion, is there a need for the spider still?
Since the blades are rotating there going to automatically want to go flat. The only reason I can see for keeping it is so the VC doesn't scrape on the magnet assembly (which it probably will anyway)
I can see this getting out of hand... 😀
I've cut apart an 6.5inch speaker that I accidently bent the basket on which should be good for atleast 100 w rms with a bit of venting. It also has a convenient hold running through the centre of perfect size.
Going to collect some fibreglass sheeting (similar to pcb fibreglass) to make the fan. Only thing I'm missing is a decent motor but I've got some remote control car one (rs540 I think) which will do for a test at low voltage
As a general quetion, is there a need for the spider still?
Since the blades are rotating there going to automatically want to go flat. The only reason I can see for keeping it is so the VC doesn't scrape on the magnet assembly (which it probably will anyway)
I can see this getting out of hand... 😀
If you ever decide to buy a motor for this application, get a synchronous AC motor or a servomotor because the rpm of these motors is dependant on frequency.
Also it might be usefull to stick a big weight on the axis to store energy for a more constant rpm.
Also it might be usefull to stick a big weight on the axis to store energy for a more constant rpm.
bass head
Hey, do what you want, GOSH! Save $13K and build one. At that rate, build two, you could save enough for a down payment on a good pair of speakers! Nothing like sitting around listening to LF test tones. Wow, a bass head. Neat.
Hey, do what you want, GOSH! Save $13K and build one. At that rate, build two, you could save enough for a down payment on a good pair of speakers! Nothing like sitting around listening to LF test tones. Wow, a bass head. Neat.
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