The process of finishing up the subwoofer is relatively similar to finishing up the other speakers. Instead of acoustical foam or Black Hole 5, I use polyester fill. Subwoofers are generally filled with a larger amount of acoustical dampening material, and as a result, I generally opt for the cheaper, more compressible option of poly fill.
The subwoofer has no independent crossover, only an active variable crossover built into Dayton 100W plate amp
from Parts Express, so there's nothing to do there.
Connect the speaker wire to the binding posts on the back side of the plate amp and install the amp into position in the hole that was previously cut out of the back.
Route the wires through the speaker cabinet, tying them around a support bracket to reduce wire tension in the event of a snag, and then twist them around the leads coming from the sub woofer driver.
Solder all connections.
Finally, install the subwoofer driver into position on the front of the speaker by drilling pilot holes and then screwing it into position using pan head black finish screws.