# Fan is a subwoofer



## toecheese (May 3, 2006)

http://www.rotarywoofer.com/

I thought this was a hoax at first, but it seems to be pretty for real. Very interesting how using variable-pitch fan blades with a CV motor can greatly increase the swept area for LFE.


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## Darren (Apr 20, 2006)

Yes, it is for real. I was following a thread over at the cult on that. I believe it is $15,000 for one presently


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## toecheese (May 3, 2006)

Well, when I think IB/DIY, I don't think $15k! It is a really cool concept though; I've been working through the math on it today in the patent for it.


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## Darren (Apr 20, 2006)

You got farther than I did  That stuff is over my head, I heard the price would be substantially less if it ever went to market but I have a feeling the demand wouldn't be that high so the price would probably remain well above "reasonable". I'd LOVE to hear one though.


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## toecheese (May 3, 2006)

Do some googling- there are some videos of it at work (a helicopter sound was cool)- though they can't do it justice for the low frequencies unless you're there in person, I suspect.


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## Danny (May 3, 2006)

Sounds good but can you use it as a fan as well? :laugh:


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## JimPeitersen (Jul 15, 2006)

I believe that they are "marketing" them now, as I think I saw an ad in the latest Stereophile (don't think it mentioned a price).
JP


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## Ayreonaut (Apr 26, 2006)

Kingjamez at CotIB says he's building a DIY rotary sub!



kingjamez said:


> Yea, Bruce Thigpen is the reason I need the amp. I'm trying to build a DIY rotary sub and have got all the parts on order. I just needed an amp that can actually drive it. I'll use Speaker Workshop to test the amp (and my sound card) and see if it will actually produce subsonic frequencies.


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## alan monro (May 9, 2006)

If one realy wants to be buffered by lots of moving air ,stick your head out of a car window while moving. A very unpleasant feeling unless one happen to be a bikie...........It is a lot cheeper than buying a glorified fan Kind regards alan


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## Guest (Oct 17, 2006)

alan monro said:


> If one realy wants to be buffered by lots of moving air ,stick your head out of a car window while moving. A very unpleasant feeling unless one happen to be a bikie...........It is a lot cheeper than buying a glorified fan Kind regards alan


not even close to the rotary woofer. There is no net displacement of air, unless, truly, there is a DC signal or offset. You also won't feel ill or nauseous at all... the SPLs to get there are achievable, I suspect, by the TRW, but my room would be destroyed far before I got there.


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## alan monro (May 9, 2006)

Tzuzz I agree,My eardrums would be wrecked before the room was. I know of a bloke that ignored a "do not enter this area " warning on the top parts of a cruise ship ,This area was reserved for the ship FOG HORN.So it happened that day was foggy , the results,he is now permantly deaf as a lamppost.Kind regards Tzuzz,alan.


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## Guest (Oct 23, 2006)

I removed the remainder of this post since a moderator or admin deleted sections of it and failed to post to that effect


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## Jerm357 (May 23, 2006)

alan monro said:


> Tzuzz I agree,My eardrums would be wrecked before the room was. I know of a bloke that ignored a "do not enter this area " warning on the top parts of a cruise ship ,This area was reserved for the ship FOG HORN.So it happened that day was foggy , the results,he is now permantly deaf as a lamppost.Kind regards Tzuzz,alan.


 WOW how loud do you think the fog horns were to cause him to go instantly deaf?


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## Danny (May 3, 2006)

I think (from memory) that at 150Db your eardrums will burst


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## Sonnie (Apr 11, 2006)

Hey guys... let's try to keep this on topic... thanks!


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## Chrisbee (Apr 20, 2006)

alan

You don't need to stick your head out of the window.

Very high levels of VLF (flutter) are possible when driving reasonably quickly with one window partly open. Presumably the car becomes a Helmholtz resonator excited by the turbulent airflow across the open window. Like blowing over the top of a very large bottle. 

I haven't tried adjusting window height to see if the frequency changes noticeably as it might with variations of reflex port area. I prefer to concentrate on my driving.

I think you are much too dismissive of a clever technology with this fan subwoofer. Who knows where further development might lead? The first example of every successful invention is rarely the final evolution. I wonder what Alexander Graham Bell would think of a G4 mobile phone?

The question is not whether the fan subwoofer works but whether the world needs or wants it it. Is the average HT nut willing to buy it in sufficient quantities to warrant manufacture on a much larger scale? And if he did, would civilisation survive high level infrasonics in every home that could afford it?


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## Bob in St. Louis (Oct 21, 2006)

Sorry to revive a one year old thread, but is there any new news?

Bob


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## toecheese (May 3, 2006)

The last I heard, a bunch of people were making some version of the rotary fan woofer to varying degrees.

Personally, after sREWing around a bunch and setting up my dual 18 IB, I don't think the ultra-low frequencies are necessary anyway.

What I mean is that, I can't hear or feel these very-low effects under 25 Hz or so. Maybe it was the series of Van Halen (I'm talking pre-sammy, pre-1984, *real* rock) concerts. 

In any case, I'm thinking if I want true LFE, it'll have to be with buttkickers, or somesuch. Doing it through the air is just too inefficient.

Since the old comparison I used to do with theaters was "is my sound better that what I'd get at a theater", I passed the "absolutely, yes" mark a while ago. I don't think any theater has such a contraption, so I'm wondering who is using this stuff anyway?


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## Scuba Diver (Sep 28, 2007)

umm ok. It might be great in a hot room. I wonder if it will work with my centeral air conditioner. All kidding aside, the real question is why. Is that price for real?


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## Chrisbee (Apr 20, 2006)

toecheese said:


> The last I heard, a bunch of people were making some version of the rotary fan woofer to varying degrees.
> 
> Personally, after sREWing around a bunch and setting up my dual 18 IB, I don't think the ultra-low frequencies are necessary anyway.
> 
> ...


I can only suggest that you are rolling off too early due to a rumble filter somewhere or you haven't enough displacement. Even my humble PCI can play infrasonic fireworks completely silently. My 4 x 15" IB can produce much more of the same. If you get 100dB @ 10Hz (uncorrected SPL meter) from your IB doesn't your hair shake if you go close enough? At around 15Hz doesn't the air in the room seem to go thick? Slightly lower again doesn't it feel as if your head is pumped up with air? Mine does all of this with hardly a sign of cone movement. Are your speakers in phase? Perhaps you need a house curve?


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## toecheese (May 3, 2006)

Yeah, when it is in the low 20s, I can 'feel' a vibration in the air- and in certain movies, it really adds to it. 

The new IB is new, and I really haven't put it through the paces yet. I have power and xmax to spare, so I can really turn it up, but yes, I do have a housecurve, and could make it a scary one, but not sure how high I need to go...


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## Chrisbee (Apr 20, 2006)

Perhaps your IB simply needs to be a little bit hotter compared with your speakers?
SPLs are vital for maximum effect at such low frequencies.

The fan sub story seems to have gone quiet again. 
There were rumours of a much more affordable model in the pipeline.
The Fan Sub website is still claiming that cone subs cannot compete.
That may be true below 5Hz but a few good 18" cones in an IB would go a very long way down without costing the earth.
Place them in a manifold under the floor and you need never know they existed.
Until, that is, the monster is called forth from its dark lair. :hide:


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## Bob in St. Louis (Oct 21, 2006)

Thanks for the reply toecheese. I was hoping to find some fellow that's DIY'd one of these. I think they could be a viable piece of equipment, but not at current prices.

Chrisbee, you wouldn't happen to have a link to the fan club guys would you? When Google searching, all I find is Thigpens unit.

Thanks guys!
Bob


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## Chrisbee (Apr 20, 2006)

Sorry, Bob. I'm not sure what you mean by "fan club guys"? 

I only know of the Thigpen as a successful project. 

There was some input from Bruce Thigpen on the Cult of the Infinite Baffle forum under general topics on Page3. The thread is called "One amazing subwoofer".

There are lots of links on this page: http://www.rotarywoofer.com/ 

(Scroll down to further links on the right for another page of links) 

The owner of the first installed pair had a construction blog and posted on a number of forums I think. Very patient chap. He answered a lot of questions.


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## Bob in St. Louis (Oct 21, 2006)

Chrisbee said:


> Sorry, Bob. I'm not sure what you mean by "fan club guys"?


:sarcastic: Sorry about that dude, my fault. I meant fan sub. You had mention the "Fan Sub" website and capitalized the letters which gave a certain amount of signifigance, I had the impression there was s specific place you were talking about. (is it the rotarywoofer.com site, or is there another?)

I'll check out the cult, thank you for that, sounds like it might be a good thread.

Bob


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## Chrisbee (Apr 20, 2006)

I think diyAudio forum had a fan sub thread with a couple of people threatening to build alternatives. Somebody was making a cylindrical centrifugal fan sub. Rather sophisticated too judging from the images.

I am still at a loss to explain the TRW fan sitting in a hard edged box in the videos and images online. Some sort of radius or fairing would surely have reduced the noise they experienced? This seems such an obvious point that I wonder why they haven't done anything about it. The airflow must be highly turbulent at the rotor tips where the velocity is highest. What am I missing? :scratchhead:


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## Bob in St. Louis (Oct 21, 2006)

I agree, on all counts Chrisbee. They've got some problems from what I've read on the net. I've recently made a financial commitment to going down this same path and am nowhere near their prototype, so I won't speak of "how easy it is". But some of their issues _SEEM_ like they'd have obvious solutions. I've bumped numerous threads on numerous forums gathering information, including a Cult thread you were posting in a while back. I've received lots of links (like yours, and thank you for that), but no real solid DIYers out there. I suppose it's due to one of two things; #1 Nobody really _WANTS_ to DIY one of these, or....#2 Nobody wants to _TELL_ what they're doing?????? 

Bob


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## Chrisbee (Apr 20, 2006)

I would imagine transient response is the major difficulty with fan subs.
Even at UVLF there is still a need to start and stop a note or effect abruptly.
The chuff of a great organ pipe is quite different from the way some pipes slowly breathe themselves into life. 
Albeit an octave higher that the fan sub can manage.
Even underpinning an LFE explosion must still require a leading edge, sustain and decay.


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## Bob in St. Louis (Oct 21, 2006)

I'll be going the way of the VC to pitch the blades. It seems logical since that's what drives a cone in a typical driver. This "should" take care of attack, sustain and decay. I've been saying, "should", "I think", and "maybe" a lot on this project. My system will end up being quad ampped by the time this is all said and done. The fan will only go up to 30'ish'. IB above that, and so on....
I've got the 'real complicated parts' on order. Should be a week of so before the sparks fly. :yes:

Bob


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## Chrisbee (Apr 20, 2006)

Bob

A voicecoil is working against a lightweight cone with limited inertia and limited air mass working against it. 

A fan has much heavier blades and is shifting relatively massive quantities of air.

The blades have centrifugal force acting against the support bearings producing friction and possible backlash.

Electro-pneumatics would seem to offer the sort of power required.


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## Bob in St. Louis (Oct 21, 2006)

Interesting Chrisbee. The VC I'm using is from a tactile transducer. My thinking is that it's capable of 'heavier loads' as opposed to a typical driver that moves a very lightweight cone.
Regarding centrifugal force, I wasn't "too" concerned as I've witnessed the forces my piece endures during it's normal use. I'll be running a fraction of the RPM it's made for. One of my concerns was whether the blade should be install on it's centerline or not. What happens to the blade at idle? Will it flutter when no LFE content is being fed to it??? That's a concern.

I had not thought of, or checked into Electro-pneumatics.....

One thing I've noticed in my searches Chrisbee....The only common denominator in this technology seems to be _YOU_. :bigsmile: 
Your name seems to pop up on all the treads I've seen. LOL
Have you DIY'd one of these?

Bob


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## Chrisbee (Apr 20, 2006)

Bob

I'm just curious about almost everything. I post to obtain answers and to float ideas always hoping to be shot down in flames by a knowledgable expert. I have had so many hobbies even I can't remember them all. There are parallels you'd never imagine unless you've played in lots of totally unconnected fields. I have spent my lifetime in libraries with nobody to share new ideas in casual everyday conversation. Now we have the internet and staggering amounts of information but most of us just sit typing instead of actually making things. Many forum members never post their experiences which I think is a terrible tragedy.

I've played with all sorts of subwoofer ideas but nothing in this line. My own very modest IB offers 8Hz(-3dB) which isn't bad from 4 cheap 15" drivers. I get 100dB @ 10Hz well within Xmax limits rising steeply in output with increasing frequency. I keep waiting for somebody with a load of 18" IB drivers to post their test results. If I can get 8Hz they must be getting well below 5Hz at very useful SPLs indeed. Why don't they share their response graphs to give everybody an idea of their success? 

There has suddenly never been a better time in history for reproducing bass. Finally everything has come together for various unconnected reasons:

We have highly enjoyable ULF programme sources from film DVDs with LFE and bassy music CDs. Cheap pro power amps can move lots of large drivers with very suitable specs. These are constantly improving thanks to serious competition between enthusiastic manufacturers and demanding fans. ThomasW has popularised the IB manifold to kill mechanical vibration and give free reign to the big new drivers. JohnM has given us easily affordable test methods thanks to REW and affordable mikes without having to spend a fortune in lab electronics. Finally cheap room/response correction electronics allow us to shape audio responses to an unbelievable degree. 

This assembly of vital components has never happened collectively before. Certainly not at prices that ordinary people could afford. Vinyl LPs couldn't manage it. Low power stereo valve amps just wimped out at the sight of a 12" driver. Corrugated surrounds on stiff PA drivers were no good to us at all. Passive crossovers were absolutely hopeless at 80Hz. 

These are exciting times for somebody who has spent 40 years just trying to obtain real bass from his audio system.

Perhaps I just like talking too much.


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## bobgpsr (Apr 20, 2006)

40 years ago, I remember, things started to change. Transistor power amps for low impedance transformerless drive. Rubber treated surrounds for woofer drivers. (Before the term subwoofer was used). Big bass reflex (aka ported) with (trial by error) tuning the port for DIYers. But unless you used tape, turntable rumble & feedback was a real problem.

You are right -- things are much better and able to be modeled now.


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## Bob in St. Louis (Oct 21, 2006)

Chrisbee - *MAN*! Almost everything you said should be posted for all to see. Not hidden somewhere in a deep dark revived thread. Very true Sir! Very true indeed. Amen brother, Well said!
Your first four paragraphs hit the nail on the head.

But......This one might just get you in trouble with a few folks, me included:



Chrisbee said:


> Low power stereo valve amps just wimped out at the sight of a 12" driver. Corrugated surrounds on stiff PA drivers were no good to us at all. Passive crossovers were absolutely hopeless at 80Hz.


You **** near described my entire system. 
The exceptions are that my tubes will be running passively crossed, pro-audio fifteens. (note: my avatar)







:yes:

Bob :bigsmile:


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## Chrisbee (Apr 20, 2006)

Bob

Your imagination for organic speaker design knows no bounds.

But where's the matching subwoofer dinosaur arching over its victim and ready to strike? :nerd:

bobgpsr

At least in Europe building an affordable 10Hz subwoofer with 120dB(C) capability at low distortion levels was alien technology. Those who took their bass seriously in the early 60s probably had to learn to be bricklayers. Or owned a new Jaguar. 

Turntable rumble and warp tracking was indeed a serious problem with many ported designs. Even if we had known how to harness that VLF output there was no cheap source material to feed the resulting device. I can still remember the frustration of listening to organ music on vinyl using my huge cylindrical, folded horn woofer fed by a Mullard 510. The only decent bass on those LPs was the bus passing the cathedral where the recording was made! I was a regular visitor to organ recitals back then. There were a couple of local "venues" with 32 foot pipes. 

This gives me an idea. onder: I may still have a couple of old organ LPs stashed away somewhere. I ought to fire them up on the IB to see what is actually hidden in those tired old grooves. (other than the No 32 bus changing gear outside)


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## Bob in St. Louis (Oct 21, 2006)

Chrisbee said:


> Bob
> 
> Your imagination for organic speaker design knows no bounds.
> 
> But where's the matching subwoofer dinosaur arching over its victim and ready to strike? :nerd:


It's in the works. :yes: 
_ALL_ of my drivers will be receiving 'new clothes'.....Too many projects, too little time. I was nearing the start of Coaxial and Augie baffles (phase I), and Sterling Augie's in IB (phase II), and rear Coaxials in radials (phase III), but then I've started down this this rotary path.....:sarcastic:
I'll have hovering dinosaurs soon enough. Thanks for (what appears to be) a complement. I do have a very active imagination when it comes to speaker design. Boring stuff sucks. LOL 
A fellow can only stand to looks at so many MDF baffles before his eyes glaze over, you know? ha ha

Bob


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