A few months ago, I went to a garage sale and picked up this old subwoofer for around $15. It's been sitting in my music room waiting to be put to use. Today I finally got around to building a new bass amp.
There are two different kinds of amps: combo, and a stand alone head which is used in conjunction with a cab. For my bass, I have a small combo bass amp. Because it's a combo amp, and has a built in head, there is no need to go buy a new head for my custom cab. To take advantage of the combo amp, I drilled a hole in the back to add a 1/4 inch jack. I soldered a connection from the output of the head to the output jack. The jack I used also has a bypass for when nothing is plugged in which I wired to the speaker. This way, if I do not have my cab plugged in, the combo amp can still function.
The original setup for the subwoofer was basically two separate speakers which you would connect to a stereo system with two wires. I took a standard 1/4 inch patch cord and striped the ends of it to be the equivalent of the two wired used in a stereo stem. I then plugged the 1/4 jack side into the newly modified combo amp. I plugged in the bass and played around to make sure it subwoofer's speakers worked properly. I then started stripping the subwoofer and removing the fabric. I then separated the speakers from the enclosure and then got to work on enclosure for my new cab.
After a few hours I finally had a nice box to place the subwoofer speakers. I covered up the front panel with cloth, stained the wood, and screwed everything together. I am quite happy with the final result. It both looks and sounds nice.