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Topic: Rotary Subwoofer (Read 4460 times) previous topic - next topic
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Rotary Subwoofer

I was searching for something else, and found this...

http://www.eminent-tech.com/main.html
(click the tabs across the page below the title for sections).

Basically the air flow from a fan is modulated by the audio, by adjusting the angle of the fan blades in response to the audio signal.

This doesn't seem to be an April 1st joke. It will cost you over $20k.

There's also a (poor!) video on YouTube...
http://www.youtube.com/watch?v=E7Bkrypxzs4

I bet you could use a simpler fan, and a far simpler shutter system for a similar effect.


Myself, I'd be happy with 30Hz!

Cheers,
David.

Rotary Subwoofer

Reply #1 –
..and here's me thinking a rotary engine would be involved

Rotary Subwoofer

Reply #3 –

Quote
Myself, I'd be happy with 30Hz!



I dunno, but  my diy back to front isobaric ported active sub goes easily down to 20Hz;
any lower the deq 2496 I used to equalize would not measure.

Rotary Subwoofer

Reply #4 –
The problem is you need to use nothing but class A amplifiers otherwise you lose the most important feature of that speaker, the ability to properly play back a DC offset.

Rotary Subwoofer

Reply #5 –
Interesting.  In the late 1800 Thomas Edison was issued a British patent for using a tank of compressed air, some sort of modulating valve, and a huge horn.  This isn't exactly a new idea.

I used to play in my high school band years ago.  If one stands in front of a brass or woodwind instrument, there is a DC component there.  Not sure there is any value in trying to reproduce it though.

Rotary Subwoofer

Reply #6 –
Heard it.  Yes, it's pretty amazing.  The demo room was in a hotel with a drop ceiling, and drop it did...dust and particles...during the demo.  What's most amazing is that there's material in recordings and soundtracks that is down at 5Hz and below.  Talked with the designer, interesting dude from Texas.  My question was, since the device needs to work by varying air pressure, and the back side is typically another room or attic, what do you do about the neighbors?  His answer: "Invite them over!"

No, you don't need a Class A amp for DC, any class direct coupled amp will work fine.  Class A refers to a method of biasing an active output device, not the amps capability of passing DC.

Rotary Subwoofer

Reply #7 –
Quote from: dc2bluelight on
No, you don't need a Class A amp for DC, any class direct coupled amp will work fine.  Class A refers to a method of biasing an active output device, not the amps capability of passing DC.
Let me correct that... in fact, the classic SE Class A won't pass DC because the raw output will have a constant DC offset on it that must be blocked somehow, so you want anything but.

Rotary Subwoofer

Reply #8 –
Quote
I used to play in my high school band years ago. If one stands in front of a brass or woodwind instrument, there is a DC component there. Not sure there is any value in trying to reproduce it though.
I don't think there is a true DC component (i.e. constant positive or negative air pressure) in that asymmetrical/offset waveform, and you should be able to reproduce it with a regular speaker. 

For example, you could put a rectifier in series with a speaker, and that would generate only the positive-half or negative half of the acoustic waveform, but that's not the same as zero-Hz DC.
 

Rotary Subwoofer

Reply #9 –
With "acoustic DC" do you mean something that is measured with a barometer? While impressive on measurements, I fail to see the practical usage of that for music playback. Most microphones, electronic circuits ets are designed to filter it out.

Now, having high-efficiency, high max spl, low volume units capable of rendering "close to DC", that sounds interesting. I have seen rotating fan concepts before, dunno what happened to them.

-k