We've got two 4" shielded speakers from Happ.  On the top is a stereo potentiometer for controlling the volume.  This was assembled by following Oscar's volume control instructions.

On the left you'll see a 1/8" stereo phone plug.  This attaches to an extension cable mounted in the cabinet, which then runs to the soundcard in the PC.

On the right are two crimped quick-disconnect plugs that bring in 12V power for the amplifier.  Speaking of the amplifier, that's the circuit board in the center.  Here's a closeup:

This was purchased as a kit from CircuitSpecialists.com.  Specifically, Kit 88 - 10W Stereo Amplifier Module Kit.  For $14, it's hard to beat and is plenty loud.  I also picked up some self adhesive wire tie blocks from Circuit Specialists, as the prices were pretty good.

Add a cheap black knob and some 4" speaker grilles from Radio Shack (bought years ago, evidently they no longer sell speaker grilles) and this is what you get:

Again, that's Happ's black pica vinyl.  Did I mention that I like the stuff?

Click here to move on to the electrical section.