I'm on a tight budget here, but I had an idea that's either insane or brilliant. I was given a broken home theater subwoofer a little while back, and I wasn't really sure what to do with it. I messed with it enough to figure out that the speaker cone is good, but the rest of the electronics are pretty knackered. So here's my idea: can I take all the electronics out of the cab except the speaker cone, solder on an input jack, and use it as a bass cab? I'd buy (or build) a head for it, but this would help me cut back on costs. It's a big ol' boy, called a Miller & Kreisel V-125. That company went out of business years ago, but specs for it can still be found. Any input or tips are welcome.
You want to play a bass, into only a sub-bass woofer?
Would you play a bass into only a tweeter?
Same difference.
Use the right tools for the job.
It may seem counter intuitive, but doing a DIY to save money, rarely ever works out to actually save money.
In your case, you end up with a cab that sucks all the power from your amp, to move the speaker cone in a fairly non-audible fashion. Or at least in a manner that doesn't correlate well to the bass.
Bass speaker/cab design is really a science. Guitars and subwoofers can both get away with sticking something in a box and throwing power at it. Amplifying the electric bass is much more of a balancing act.
To do justice to the usable range of frequencies, the bass requires nearly a full fidelity system fine tuned for the special needs of the bass.
As long as all of this is clear to you, and you know that it's just an experiment going in, one that might work, or might not, then that's fine. But if you plan on this being your main player, and it is important that it sound right, you are more likely to be disappointed than not.