PVC theremin diamond speaker project

Posted: 11/25/2009 11:17:39 PM
Thomas Grillo

From: Jackson Mississippi

Joined: 8/13/2006

Hi all,

I've finally found a bit of free time over the last few days in which to throw together my first theremin diamond speaker. It's made of PVC, and here are some pics of the progress which shows the diamond with only the speaker temporarily mounted to check ballance, and loading, and with the soundboard, which is plaxiglass, with some holographic sticky film covering it.

Posted: 11/26/2009 4:21:40 PM

From: Kansas City, Mo.

Joined: 8/23/2005

Looks cool!
Posted: 11/26/2009 6:02:18 PM
Thomas Grillo

From: Jackson Mississippi

Joined: 8/13/2006

Hi Kevin, Thanks. I still have some details I want to add, like art deco stuff for the corners to hide the fact that it's made of pvc pipe, as well as a new speaker. This speaker is from an old rms 100 amp, and it's cone's just about had it.

Happy thanksgiving! :)
Posted: 11/29/2009 1:39:00 PM
Thomas Grillo

From: Jackson Mississippi

Joined: 8/13/2006

I've added a few new pics of my latest progress. I've installed some black sequin fabric to the soundboard, and added a thin aluminum frame.
Posted: 11/29/2009 11:43:03 PM

Joined: 9/12/2009

Well it sure does look cool, Thomas!

Is it open-backed or do you have something covering the back of the speaker?

Posted: 11/30/2009 11:50:04 AM
Thomas Grillo

From: Jackson Mississippi

Joined: 8/13/2006


At the moment there is no baffle on the back of the speaker, but I'm wondering what this would do for the sound.

Posted: 11/30/2009 1:22:07 PM

From: Colmar, France

Joined: 12/31/2007

Theory: An open speaker without housing risks to produce less bass because there will be a kind of acoustic "short circuit" between the front and the rear radiated sound energy. This effect concerns frequencies below ca. 80Hz (depending on the speakers' size and his resonant frequency) which is rather not important for theremins. Building a case for a speaker is always a difficult compromise between frequency response, impulse response and size in order to get still something out below the speakers' own resonant frequency.

So a mounting panel (which partially reduces this short circuit effect without modifying the speakers' frequency and impulse response) seems to be the best solution for a theremin.
Posted: 11/30/2009 7:09:41 PM
Thomas Grillo

From: Jackson Mississippi

Joined: 8/13/2006

Thiery, Thanks for the information. I'll certainly go for an enclosure on the back side of the speaker now. :)
Posted: 11/30/2009 8:00:34 PM

From: Canada

Joined: 8/1/2008

Thomas, what Thierry says regarding the cancellation of certain frequencies when a baffle is NOT used with a speaker is correct, but this is not necessarily a bad thing. It depends on the qualities you want your sound to have.

I don't use a baffle on my theremin speakers because I like the more delicate "human" tone of the naked cone. Don't forget, the resonating chamber of a human soprano, including the throat, mouth and nasal cavities, is not quite as big as a pint of milk.

Ideally, you should have more than one speaker, then you could switch according to the piece you're playing and the acoustic effect you want the music to have on your listeners.

I have found that the sound of a theremin is often more "alive" when it is tender and fragile. A speaker/amp array that is perfect for a keyboard synth or an electric guitar is not necessarily ideal for a theremin.

It's just something to think about.

Remember: LESS IS MORE

Posted: 11/30/2009 9:48:23 PM
Thomas Grillo

From: Jackson Mississippi

Joined: 8/13/2006

Coalport, I see what you mean. While playing without a baffle, I noticed a trade-off from cello like to more high voice-like tonal charactor.

I just tried a cardboard shell behind the speaker, and I did notice less "delicate' qualities, and a bit stronger mid / bass charactor come in that was never there when I had my speaker still on it's old board behind me.

Thanks for the information. :)

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