For you electronic geeks out there, this is essentially the same thing as a two channel oscilloscope being used in XY mode. The idea is to use the speakers so that the sound they would be playing moves a laser beam instead. One channel moves the beam left and right, and the other channel moves the beam up and down. With this arrangement, music will show up as an everchanging light flower on your wall.
How Stuff Works has a great little diagram of a speaker in action. You don't actually have to know anything more than the bare minimum of how speakers work. If we refer to a speaker part and you don't know what we're talking about, look here for the explanation.
Speakers make sound by moving a diaphram rapidly back and forth. The diaphram pushes at the air, creating the vibrations your ears interpret as sound. In this project, we're going to use the speaker's mechanism to move a mirror instead of a diaphram. When you bounce a laser beam off this mirror, it will make the beam wiggle and trace out the sound's waveform.
Take a look at the layout of the DiscoLazer above. The laser pointer toward the bottom is aimed at the right edge of the mirror on the left (you can just barely see the red dot). That mirror wiggles the laser left and right (we affectionately call it the "horizontal deflector"). From there, it bounces the beam to the top edge of the mirror on the speaker on the right. The red dot is very bright there because it's aiming the beam just above and to the right of the camera. That mirror wiggles the beam up and down (the "vertical deflector").
The beam is then allowed to land on the wall and everybody goes "oooh!". With this arrangement, if you play a sine wave through one speaker, and the same sine wave 180 degrees out of phase through the other, you'll see a circle on your wall.
We're going to tell you how to assemble one speaker. Just do the same thing with the other one (with two differences we'll mention when we get there.)
Next Page: Preparing the Speakers
| Intro | How it Works | Prepping the Speakers | Coathanger Mangling | Preparing the Mirror | Preparing the Pivot Rod | Final Assembly | Setup and Operation | Needed Improvements |