Oh. I was gona' say 10", and lots of them...Cuzme said:...for a fifteen inch 70's polytone bass combo amp.
AGCurry said:You left out two important data: How much power must it handle, and how much money do you have?
I'm guessing the Polytone doesn't push more than 200 watts. Any contemporary 15" bass-instrument speaker should be able to handle that. I'd start with Eminence. The Kappa Pro is a very good driver, but it's heavy and probably overkill for the Polytone. Check out their Delta series.