4th order bandbass subwoofer

Construction materials and tools. Started with a 4 foot by 4 foot
by 3/4 inch sheet of Birch plywood which they cut off at 17 1/5 inches
so I could fit it in the car and the smaller piece contained the top, bottom,
and one side, and the other piece had the remaining side, 2 ends, and the
baffle in the middle with the driver.

In this picture all the pieces are just resting against each other.
The chamber at the top is sealed and in my box the speaker actually points
backwards into that rear chamber. The front chamber has a 3 inch port which
isn't cut out in this picture yet. See the next one.

Ok, this is testing. The sub is on the left and you can see the hole in the side of the
enclosure. That's a 3" vent opening into the front chamber. In this picture the wires are running
out through the vent but they'll be replaced with some better type of connector, probably some
fancy speaker posts running through the box. At this point it's lightly screwed together. The next
step is to glue all the joints and seal them with silicon sealant or hot melt glue. The presure inside
the sealed chamber is meant to be quite high to act as an "air spring", and right now if I crank it
up the box starts to rattle. It'll be glue, sealant, and then a few more screws just to be sure. They
say that an elephant should be able to tap dance on your sub. I can see why now.

The black thing on the floor between the sub and the stereo is the
ParaPix subwoofer amplifier, and out of view behind it is a 48V AC
transformer. The Parapix will happily crank out 60 watts RMS two
channels (mono signal amplified twice), which I hook to each of the
coils on the dual voice coil 8" sub. The ParaPix has a built in variable crossover,
level control, and a jumper which turns on a 12dB boost below 30Hz.
I plan to build a separate enclosure for
the amplifier instead of trying to fit it into the side of the sub enclosure,
because then I can use it to drive a bigger sub in the future if I want
and the bandpass box will always be useful as a passive standalone sub.

The ParaPix amp cost me $20 and the transformer another $20. The 4x4 sheet
of Birch cost $36 (ouch.. 4x8 would have been $56.. should have done that
but I didn't know if this thing would work).
The PVC pipe for the port cost $0.55. Misc screws a couple bucks.

Of course it was an excuse to buy a saw too.