Electromechanical modulation?

[dano12]

It's been a while since I posted something strange. This came to me in the shower this morning. Sound remotely feasible?

[KerryF]

Freaking insane idea! 

I would love to see this built!

[Seljer]

speaking of tubes with speakers in them, I saw this earlier today: http://www.youtube.com/watch?v=HpovwbPGEoo&eurl=

[puretube]

http://acapella.harmony-central.com/forums/showthread.php?s=&threadid=1114460
http://acapella.harmony-central.com/forums/showthread.php?s=&threadid=1188539

[Plectrum]

Sorry to simplify, I'm sort of thinking in text... (warning - amateur physics monologue in progress...)

I have a feeling any sense of modulation would be minimal.
The rotor horns of a leslie provide a smoothly moving "conduit", that "sprays" the soundwaves out into the cabinet.
The path/distance to the mic is changing smoothly. As the horn apperture approaches the mic, the soundwaves will rise in pitch and vice-versa.

In the tube, the disks will either reflect or pass sound depending on position.
So, you will get full direct signal when the appertures are aligned, and some reflected/phased sound when they don't.
I think the overall effect being a little like someone mixing a fixed-freq phaser in and out - which, I think, isn't something the human ear/brain finds that "noticable" or "exotic" in this sort of application. Reflections would diffuse the effect further (ie. even with aligned appertures, and a direct speaker-to-mic path there would be a high ratio of reflections).
You'll also get a strong peak at the resonant frquency of the tube, which may restrict choice of scale/size .

Grant

[Plectrum]

Oops... How do you delete an unintentional post on this forum? (this one)

[John Lyons]

In other words the effect layed out above will be more of a vibrato where the volume goes up of down in a choppy fashion with speed depending on the rate of the discs rotation. A true leslie takes advantage of the doppler effect by the distance between your ears and the horn and or walls and hard objects the cabinet it in and next to. The sound is like when I siren or ambulance drive by you on the street. The pitch rases as it gets closer and lowers as it leaves you and gets further away.

A few things happen here.
The Horn spins around.
The horn gets nearer and farther from your ears causing pitch changes up and down.
The horn is off center. Picture two funnels with the two small ends touching and forming a straight line. One is a dummy horn for balance/symetry of the mechanism, the other horn is active and connected to the speaker driver "spraying out sound".
It's a matter or close/far sound and direct and indirect sound. Very complex and very cool and unique. The leslie sound is Just as unique as the Hammond organ which pairs to make the ultimate combo sound source. If you never heard a real one you don't know what you are missing. It's truly 3-D sound. Not like stereo, way more than that. Pitch, volume, phase, etc.

The down side is that they weigh hundreds of pounds and haven't been made for years!

Not that the effect above won't be cool, just nothing like a leslie speaker. There are too many factors involved to be contained in a very small space.

John

[Plectrum]

The down side is that they weigh hundreds of pounds and haven't been made for years!
John

They are being custom built, and the newish Leslie 21x1 are hybrid dig/mechanical (top rotor is mechanical)

Piccy Halfway down this page:
http://www.soundonsound.com/sos/jul05/articles/hammondxk3.htm

Grant

[Meanderthal]

 This one put a smile on my face! With reduction gears and using the butterfly valve method this might get pretty interesting... and also multiple mic elements. You would need to do something about mechanical noise- maybe shock mount the mic/mics. The tunable chamber is a great idea, in a blue man kinda way... hehe

[dano12]

Thanks for all the great feedback--a lot to think about...

I was playing around last night with some servos that I have (from a long-departed RC hobby) and looking at constructing the butterfly valve version.

[Thomas P.]

maybe you could keep one reflection disc and try to move the speaker back and forth with the other motor...