Caution: when completed, this can be highly addicting.
Caution: this could potentially harm your speakers. It has not harmed mine for any long period of time, but it could happen.
Step 1: Remove the Speaker Cover.
Step 2: Find the Right Speaker.
Step 3: Waterproof the Cone and Dome
So, find your favorite waterproofing material (I used polyurethane) and apply it to the speaker cone and dome but NOT to the rubber around the edge of the speaker which allows the cone to move. At least not to the whole thing, it's not a crime if you get a little on there.
Step 4: The Magic!
There are three basic patterns:
The first and simplest is rings, and it looks like a standing ripple. It will change dimensions depending on the music.
The second happens with more complex music and especially bass. It appears as a bunch of high but small radius circles that will move around and interact with each other to create a constantly moving interference pattern.
The third happens when you turn the music up quite loud. The water will jump (I've had it go two and a half feet) and continue to do so in a lovely shower of drops in the loudness which will get anything within a foot or two damp.
And after the polyurethane