can car subwoofers be used as a bass cab?
I think there's a reason for them to be called "car subwoofers". As long as I know, they are with limited frequency range, more limited than guitar and bass guitar speakers, so they aren't a good solution for a cab.
I'm sure there's a way to make it work, but at the price of a good subwoofer, you can get a used cab.
You'd need to be quite a handyman to get a car subwoofer to have a patch cable plug into it. Also, don't car woofers come in 16 ohms or something like that?