M&K 5000

I have an M&K 5000 Subwoofer I have had since new.

Recently the thing started microphoning.
Every foot step in the wood floor room would make it fire at max. vol.

Went to unplug it for the first time ever with earplugs in. It still almost blow my ear drums! Grill went flying across the room!

I miss it very much! I called & talked to Ken. He had no ideas. I need it fixed. Anyone have any ideas? I am not a DIY guy. I'm in Southern NJ near Philly.
Buy a new sub, that technology has advanced significantly in the past decade...