Beer Can Leslie

Some time around the new years, I started contemplating a strange idea: could you create the Leslie rotating speaker work-alike, but scaled down dramatically in size. Because beer is just about one of the greatest things ever wrought by man, I figured that a beer can as the rotor baffle would be cool. And that would set the general scale of the overall strange thing.

There would obviously have to be some design compromises-- top-end Leslies are serious affairs with rotating horns, 12-15" bass drivers, crossovers, dedicated tube amplifiers, and big honking cabinets. So the goal here is to see how close a Rube Goldberg small-scale rotating speaker device could get to a real Leslie.

To take a test run, I gathered a 12-pack of Miller High Life (you know, it really is the Champagne of Beers), a Radio Shack DC motor. Add in a $10 mini ipod speaker, rated at 8 ohms with a power rating of 1 watt. It certainly doubtful that such a shitty driver would make an effective parts choice, but sometimes you never know. Also, I'm not sure if I am even close on the motor--can it spin a beer can at controllable speeds? I'm sure I'll find out.

Here's the front view of the speaker:

And luckily enough, the speaker dome is roughly the same diameter as the beer can.
 

I've dremelled the bottom of the can out so that the top-firing speaker has somewhere to send its air.
 

I used a small cut piece of Plexiglas for the motor mount and attached the motor with small bolts.
 

I cut a piece of aluminum sheet, attached it to the Plexiglas on one end, and to two L-brackets on the other side.
 

With the attachment of a small strip of wood to the motor shaft
(via 5-minute epoxy), the basic motor head unit is complete.
 

I cleaned up the wiring, and added gratuitous LED-backlighting and a terminal strip.

This would be my first test rig. I already had a 3VDC battery with potentiometer for speed control for the motor.

I made three slots in the can using a utility knife.

Finally, I cut a few strips of cardboard to act as an internal baffle. This baffle design, along with creating only three slots was complete guess-work.

Beer Can Version 1 Results

To test the effect, I plugged a guitar into a Noisy Cricket amp, and the output of the amp into the cheap ipod speaker built into the bottom of the unit.

So after all this work, the thing actually generates a modulated signal. I'd classify the sound as about 60% pure tremolo and 40% weak Doppler effect. I attribute this relatively poor performance to a number of factors:

1. 1. There is too much clearance between the speaker and the beer can. I got it as close as I could, but to much non-affected signal is leaking through.
2. 2. The beer can is a bit to small to effectively accomplish anything more than a modulation of the upper end of the frequency.
3. 3. I need to come up with a better speed control than a potentiometer. To solve this, I'll work on a PWM motor control with an Arduino processor board.

More to come as I have time.