So you’ve found a couple of nice drive-in speakers at the flea market or swap meet and you want to restore them to use with your stereo or PC sound card?
Having been exposed to the various weather conditions for a few decades or more, they will probably be full of paint, dirt and crud so here’s a handy post to return them to “like-new” working condition but with some super power and a retro twist as a 20-watt amplified stereo speaker set with an RGB lighted dial that first dials in your volume by color and then, with a click, pulses to the beat of the music. It’s all done with 4 modern off-the-shelf circuit boards inside — but to keep the retro look, there’s an old-school toggle switch for power.
And the classy finished result will be the versatile drive-in speakers that you can hang somewhere fun, then connect your audio source. This little 20W amp provides a lot of sound!
The encoder dial will change colors as you turn the volume up and down. Now click it to make the light pulse to the beat; the little microphone board listens to the music, then the Arduino filters the analog signal to detect the beat and modulate the light.