New Subwoofer Technology

**Robert_Gibran** · **09-19-06, 10:12 AM**

Gentlemen, check out THIS http://blog.stereophile.com/cedia2006/091606thigpen/

and

THIS http://blog.stereophile.com/cedia2006/091906soundfield/

RG

**Sonnie** · **09-19-06, 10:43 AM**

Yes... the sub fan has been the subject of discussion in couple of threads. The price was a little scary... :raped:

Good to see ya out and about Robert.

**Jack Gilvey** · **09-19-06, 11:43 AM**

You're so vane...

**Mr. Lamb Fries** · **09-20-06, 08:33 PM**

Any measurments on this thing...I heard it went down to 5 hz, How does it work???

**Josuah** · **09-21-06, 01:43 AM**

I'm not 100% sure, but this is my understanding of it.

The fan blades spin (seem to be flat blades, so I'm not sure it pushes air one direction or the other, probably not or else it sitting between the two enclosed areas wouldn't work right???) and at the same time they vibrate at the frequency you are trying to reproduce. Therefore, the air being moved by the blades have the frequency.

I imagine it's a lot like when you talk into a standard fan.

**azjimmy** · **09-21-06, 03:32 AM**

It works on the same theory as a helicopter rotor. It compresses air just like a speaker, only it uses variable pitch blades to push air instead of a moving cone.
Pretty neat, really.
The video on the site is down right scary when they do the sweep. Looks like it's going to shuck a blade! You can even hear one of the guys saying not to get too close. Check it out http://www.youtube.com/watch?v=E7Bkrypxzs4
Jim

**jeffbridges** · **09-21-06, 11:00 PM**

Quote:

Jack Gilvey wrote:

You're so vane...

You probably think this song is about you, Dont you, Don't you

**Chrisbee** · **09-22-06, 06:22 AM**

There are three videos on the TRW fan sub.

It would seem to offer not so much a signal to noise ratio as a noise to signal ratio!

When I think of the lengths I went to to just to quieten the fan in my EP2500...!

**Exocer** · **09-22-06, 02:09 PM**

Whenever people mention these fan subs I always wonder how musical content would sound. Something about musical bass notes comming from fan blades is incredibly interesting to me.

**JimPeitersen** · **09-26-06, 01:57 AM**

Quote:

Exocer wrote:

Whenever people mention these fan subs I always wonder how musical content would sound. Something about musical bass notes comming from fan blades is incredibly interesting to me.

I see two issues:

Can the human ear distinguish between notes (fundamentals and harmonics) in the extreme infrasonics that this "driver" produces?

In the end, does it really matter what the transducer is since all speakers are simply mechanical interfaces between the electronic signal and our ears (they all excite the air, does it matter how?)

JP

**Exocer** · **09-26-06, 10:58 PM**

Quote:

JimPeitersen wrote:

I see two issues:

Can the human ear distinguish between notes (fundamentals and harmonics) in the extreme infrasonics that this "driver" produces?

In the end, does it really matter what the transducer is since all speakers are simply mechanical interfaces between the electronic signal and our ears (they all excite the air, does it matter how?)

JP

1.Probably not.
2.Probably not.

However, with that said, i'd still love to hear a demo of one of these subs playing music. Music doesn't fall under the infrasonic range.With infrasonics it wouldn't matter at all what moves air because what we don't hear, we feel at those frequencies.

**Josuah** · **09-27-06, 04:21 PM**

I guess your music would have to be classical with big drums, 1812 Overture type, or taiko drumming. Since this fan stops at 30Hz, I think.

**Exocer** · **09-27-06, 05:31 PM**

Not my type of music...lol
You're right about the upper limit being 30hz though, i believe its -4db by 30hz.

I do remember reading a post on another forum regarding low frequency information in modern day music getting as far as the mid to low 20hz range. Wish I had that link...

**Josuah** · **09-30-06, 03:57 AM**

Not sure what "modern day" means. :P But there have always been some "pop"ular songs that incorporated frequencies between 20-30Hz. I think Sarah McLachlan's Brown Man (something like that) has it. I think some of Leftfield's songs do.

But so what? A much cheaper subwoofer can deliver 20Hz and up reliably and definitely with enough SPL for music. My SVS subs for a 10th of the price of this sub can deliver 10Hz.

It's the rest of the music and movies that is why I need to build a sub that hits 5Hz....

**Exocer** · **09-30-06, 11:06 AM**

Quote:

Josuah wrote:

Not sure what "modern day" means. :P But there have always been some "pop"ular songs that incorporated frequencies between 20-30Hz. I think Sarah McLachlan's Brown Man (something like that) has it. I think some of Leftfield's songs do.

But so what? A much cheaper subwoofer can deliver 20Hz and up reliably and definitely with enough SPL for music. My SVS subs for a 10th of the price of this sub can deliver 10Hz.

It's the rest of the music and movies that is why I need to build a sub that hits 5Hz....

Indeed, a much cheaper sub can hit from 20hz and up..No disputing that. I don't see how that has anything to do with my comment, especially because I specifically stated how interested I was in hearing the rotary sub producing those bass notes, not a much cheaper sub.
Oh and by modern day music I meant todays pop music... guess my terminology wasn't clear. My apologies.

Quote:

It's the rest of the music and movies that is why I need to build a sub that hits 5Hz....

I too would love to build a sub that hits 5hz...with enough authority to feel it. Im pretty sure both of my sealed subs are hitting this low, but with nowhere near enough output to make it even worth mentioning.

I'd imagine most people using these rotary subs aren't using these alone? Maybe have the rotary sub take care of its sweet spot, and a sealed sub take from 30hz and up...

**Josuah** · **09-30-06, 01:28 PM**

I just saw a post stating 20ms of group delay at 20Hz was desirable, by Mark Seaton. So I guess my knowledge of group delay needs to be improved.

Oh, and my so what wasn't so much with regards to your desire to figure out how the rotary sub would produce those frequencies, but a so what at the rotary subwoofer itself.

I think it might sound different, but I'm very skeptical it would sound better. That's all I meant.

**Exocer** · **09-30-06, 05:45 PM**

It probably doesn't sound any better...I bet its a ton louder though

**tzucc** · **10-01-06, 11:02 AM**

hi folks, Ilkka sent me a PM over at avsforum regarding redirected bass, which I will test today with the rotary woofer (TRW). If you want to read more about the first home theatre install for the TRW, you can check out the blog at http://bassment.wordpress.com ... avsforum ultra hi end forum has a thread as well fwiw.
We first demo'd the TRW at my house about six months ago for a group of SF Bay area audio types, and since then I have been working with Bruce to install two TRW's in my media room. We've been hard at work for the last two weeks doing the install, and it's now about complete.

Ilkka, thanks for bringing the redirected bass issue to my attention.

**Chrisbee** · **10-01-06, 12:28 PM**

How could one ever live with only a Wilson XS and two Watchdogs ever again after hearing a TRW?

It's not just about reproducing very low frequencies either. It's all about level and it's all about very low distortion.

I had a couple of enjoyable years listening to my SVS 16-46 which I have measured to 15Hz at very silly output levels. It went loud at completely inaudible frequencies. So you ask yourself what more is there?

Then you hear an IB! Everything suddenly sounds as if it goes more than twice as deep. You have to ask yourself why. Exactly the same frequencies are being reproduced at very similar levels. The only obvious difference must be the lower distortion and greater extension affecting one's senses.

The only way we mere mortals are going to get even more extension with lower distortion is by doubling the number of drivers in our IBs. Then doubling them again. 16 x 18" longthrow woofers in twin manifolds sounds like a lot of fun. I wonder how they would measure up to a TRW? The problem is you'd need a concrete cellar for a listening room to keep the house structure together. Plus an enormous volume for the rear wave to play with.

Having seen the effects of four quite modest 15" drivers I'm not sure I'm ready for more. There have been times when the whole roof above my attic listening room has stretched and groaned. Spookey! On another occasion I was leaning with all my weight on a pair of locked doors which were literally bending 1/2" away from their frames. I couldn't do a thing about the enormous forces at work. The power that was moving the doors was completely indifferent to my efforts to hold them still.

**tzucc** · **10-01-06, 01:41 PM**

the interesting issue to consider is that the 15's will drop after 20Hz in terms of reaching suitable SPLs. You have to have far too many 15's and amp power to get near the TRW's capability and then you are at massive replicated distortion. The TRW is not about 20Hz and above, in any case, but recreating the 0-20 spectrum, which does add significantly to the movie content.
For years I have been after more 20-80, thinking that would increase the reality coefficient, but it turns out that 0-20 is where the really important psychoacoustics (for bass, not overall) may in fact exist. All I can say is that scary movies are much scarier, and action movies are far more violent with this infrasonics that one can HEAR and feel. Yes, you can hear 5-10Hz... it's not tonal, but you feel the waves in your ear and body, again, assuming enough SPL. My two 18" cone drivers at 2400Watts can create SPL at 10Hz, just like any subwoofer, but it just can't make any useful amounts, even if they are tearing apart.

I suppose this all sounds a bit far fetched, and if I was reading someone else doing this a year ago, I would have been intrigued but very skeptical. The only way to understand what 0-20 does is to simply get the demo.

**Chrisbee** · **10-01-06, 05:20 PM**

I certainly believe you. When I was struggling to describe the sound quality of my IB I noted that the IB gives one no warning of impending bass fireworks. It appears from nowhere with frightening dynamics then is gone just as quickly having conveyed tremendous weight in the briefest of moments.

I believe the fast rise time is important but also the lowest fundamental frequencies carry important information that one can sense. It may be by bone conduction or it may actually be audible once certain SPLs have been reached. But it is an essential part of our autonomic sensing of the audio power behind the briefest of sounds. Since man has been exposed naturally to infrasonics for millions of years he has not dismissed these inaudible sounds in his quest for survival. Rock and tree falls, vulcanism, the size of the animal rushing at him, the roar of the cataract and the crash of the wave have all been within his daily experience.

Now we simulate the dangers which were once man's daily struggle to live another day. We have not yet lost our audio skills at seperating the mundane from the terrifying. I believe that infrasonics have remained part of our survival kit. At least for impacts and other dynamic sounds like explosions, drums, heavy footfalls and gunfire.

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