I finally wired it up like in your diagram. Seems to be working OK. Thanks a lot for your help. Should I be able to hear a slight buzzing (when my ear is a foot away from the 6" speaker)?
Glad to hear it.
Can't really answer your question without being there. (does your bass have single coil pickups; etc.)
But some general advice: don't put your head a foot away from this cabinet! it's loud.