'Air-valve' tremolo

[petemoore]

  Pretty simple, like a leslie, but simpler.
  Get sound waves travelling through a tube [say..connect a tube aligned with the hole in the baffle of an enclosured speaker] with a 'flow valve'.
  Alot like what is used in home heating systems...the valve you'd turn to block hot air through the tube [to shut off a rooms register at nearer the heat source], a disc, [about the inside diameter of the tube, inside the tube] which when turned, blocks the tube, when turned back inline, allows almost full flow...doing RPM.
  Big 'n ugly...eh ? Passive and should otherwise be tubeless/transistorless-mojo-cool sounding, I'd guess it might have a slight 'phase-twist' to it.
  Making it speed controllable and able to go 'off' [stop spinning at valve-open positiion] is where it'd start getting tricky.
  For some reason this concept has been repeatedly 'bugging me.. to build it, but it's just too ugly a thought, so I'm typing about it instead.
  ...Had to have been done before...[?]

[SeanCostello]

  ...Had to have been done before...[?]

Yes. It is called a vibraphone.

http://en.wikipedia.org/wiki/Vibraphone

Sean Costello

[dano12]

I drew this up last year. Haven't tried to build it yet

[momo]

Sean,Pete, thats a great idea!, I sat there looking at this for a while!.....heres my humble opinion on one important detail......part of the leslie sound is due partially to the Doppler effect you get by having the sound source move in distance relative to the mic/ears. So you would not get this but the phasing issues should be great, im wondering if the fact that its in a "closed" baffling.....sound pressure changes inside the closed system, and how would it affect the mic capsule.
Maybe use a small capsule omni with good wind protection.
Also, maybe using different textures on the disc......a piece or two of the pie would be wood, another piece or two, a mirror, something like that, just to fuzz it up a bit in the comb filtering effect...the idea being that the reflections of the sound from the discs, would have different content in the high end,more with the mirror,less with the wood.mixing that up at certain speeds, Im guessing you could modify the tone a bit.  Im only saying this because its in a baffle that is acoustically pure enough to hear these suptle changes on the mic.

Id love to try this!, Im actually quite facinated by this!, I just think it will give a different sound, not nessesarly like a moving sound source, but still real Funky!

[petemoore]

Id love to try this!, Im actually quite facinated by this!, I just think it will give a different sound, not nessesarly like a moving sound source, but still real Funky!
  Yes this one's had my minds eye on it every morning lately...wandering into the garage looking at shapes etc. [nothing really fits though...and
  for an electric Xmas light motor/gear housing/drive...haven't found that yet either..
  I'm thinking DC motor, maybe even two, switched..not too sure about popping issues or how leslies deal with 'quietly' powering the spindles.
  The tube I think'd do well if it had a 'socket' shape in it that followed the edge of the spinning disc around say a few inches...I would start with a couple knitting hoops and solid cardboard sheet, make a drum from ply's of cardboard [and a cylinder for use as a mold, something that could be removed], then build two blocks for the spindle/bearing mounts, they'd need to be stiffly mounted.
  The disc itself could be..a speaker baffle cutout..
  Maybe one of my turntable motor/drives or something from a VCR could be used for the motor assembly..lol.
  Eventually becoming a potential contestant for the worlds largest tremolo unit.

[Processaurus]

A vibraphone for a guitar, too cool!  Be aware though that most (all?) DC motors are one of the few electrical things that will be damaged if they get under the voltage they want to see, that's why DC motor speed controls are complex, I think they do a PWM type thing, rather than vary the voltage to the motor.

[momo]

This might complicate thing a bit and give it a frankenstien look but a pully system could do it for speed change without changing the motor speed. It might change the "pull/stress" on the motor.

[rooster18]

I posted awhile back about a method to somewhat replicate a Leslie using pitch changing vibrato, multiple oscillators to control amplitude vs. frequency shift, two different circuits for the low/high crossover effect of the horns vs. the bass speaker, but nobody seemed interested. Maybe it was a tad more complex of a concept than just improving an already designed circuit, so nobody bit.

rooster.