I've got this crappy PA cabinet from the 70's, unloaded. It's in fact been chopped down from it's original 4x12 (vertical) size to a 2x12. I've got some spare 12" car audio subwoofer drivers laying around, plenty of wattage handling. Is there any reason I can't just wire in these subs and use the cab as a low-expectations general purpose speaker cabinet...say, for running the PA through in practice where the sound quality really doesn't matter...or a guitar/bass extension cab (I know it wouldn't sound good, I just want to know if it would do any damage to the amp)? Alternatively, if this is a universally bad idea, is there a known source for really dirt-cheap speakers i could throw into it? I don't want to spend real money on it since I couldn't justify spending more than it would cost to just buy a well-used cabinet. Most of the fun is in the project but...well, you know.