I used to work for a HI FI shop that also specialized in rebuilding and repairing speakers.
Every week, we would have some sad looking guys come in with a pair of big speakers "bought from two guys in a white van"...
I usually always just removed all of the cheap speaker components (that burned up), and replaced the speakers and crossovers with slightly better parts.

The shop I worked at was close to Fort Lewis ( a large military base)... and the guys in the white vans would scam the military guys on military payday. They would wait outside the taverns and bars, and when they got the attention of a drunken military guy, they usually made a sale!

Some Mondays, there would be two or three guys waiting for us to open the store, and they would have these big POS speakers with blown drivers in them!