It's not made from a vintage boombox or ammo can, but I did scratchbuild a little bluetooth enabled combo amp over the fall. I had a $25 Ebay coupon burning a hole in my pocket and a derelict Sony shelf system sitting around, and thought it might be fun to knock something together using one of the inexpensive class-d amplifier boards I'd been seeing around the web. The amp board I chose is TPA-3116 based, and outputs in the neighborhood of 50W/channel in the configuration I run it in. I used a bluetooth media player module, a speaker protection circuit board, some 1/8" and 1/4" phono jacks as L/R inputs, a 24V switching power supply, and an adjustable stepdown converter to power the bluetooth module.
The amp board I used has an onboard EQ and is set up to be panel mounted, so I made acrylic panels to mount the amp/EQ and analog inputs to, and recessed them into the top of the cabinet. The BT module faceplate is flush-mounted into the top of the cab. The cabinet itself is styled a bit like a small stage monitor with a slanted speaker baffle and z-back profile, and made from plywood glued and screwed together with battens. It has rubber feet on the bottom and on one end so that it can be used either horizontally or vertically, and I added a wire pull handle for easy portability.
I'm pretty happy with how it came out. It works great after tracking down and correcting a couple of grounding issues with the inputs and amp board, and can be used as a stereo practice amp, a bluetooth speaker, media player via USB and SD card, FM stereo, and party and cinema speaker for outdoor movie nights with a projector.