Does anyone know of a repair shop in Minnesota or western Wisconsin that fixes subwoofers?
What subwoofer and what is wrong with it? Where do you live in Minnesota? The class D amps that are in subs, are an absolute misery to work on. The other issue is that almost no one issues service manuals any more. Without a service manual no one can begin to service a unit like that.
If you tell me what you have, and what is the matter with it, and you live in, or close to the metro, I may be able to help you if the unit is realistically serviceable. That is one reason why I have such a lot of classy older gear. Service manuals were easily available in times past, and I have been able to keep my good older gear in prime condition in the main. I have a pretty decent service area at the back of my equipment chase.