Using LED's with stereo speakers

[R1futly]

This has nothing to do with idevices but I thought maybe someone on this site could help me out.

I built a cooler stereo to use at my pool area or on float/camping trips. I was wanting to add LED's to each speaker that will flash to the beat of the music. I am using an amplifier that produces 50 watts RMS @4 ohms going to each speaker. I bought some rectangular LED's at RadioShack that have the following specs:

Intensity: 350mcd
Wavelength: 465nm (min) 470nm (max)
FW current: 20mA
FW supply: 3.2V (typical) 3.8V (max)

I was playing with one just connected directly to the speaker cable, turned it up a little too loud and let the smoke out of it. My question is what kind of resistor do I need to get the best light output but not to blow any more of them?

Thank you very much for any advice.

[ikesmasher]

im sorry i cant help you but...
Is there a tutorial or some sort on how to do this? i has some really amusing ideas from what you are trying to do...

[Zeal]

I heard google knows ask him