Computer amps work great for scanners. I've used them with the Radio Shack motors:
http://www.experimentalexperience.com/photos/sound-responsive_liquid_sky.jpg
And I plan to do the same for spiros...
The impedance is very low on those motors, so I had to add power resistors or capacitors in...
thanks for the feedback. it's actually more simple than some of your guesses. the description and comments of my youtube videos explain how it's done, and guitar string version links to a couple high-res photos. the guitar string version worked better before it got kinked from too high...
Okay, so I re-invented the wheel a little bit. Some of you are going to laugh at the simplicity of my projects, but you have to admit that it's not bad for something so simple and cheap:
YouTube - Music Laser with "Ghosts" by Ladytron
YouTube - Music Laser with Keyboard
Hi, has anybody else used these for liquid sky?
Super Speed 9-18VDC Hobby Motor - RadioShack.com
They work great, but I'm wondering how long they last...