There were many test discs with the break-in track.

The Stereophile disc's track had clanging like pots and pans with a backgroud that sounded like frequency sweeps going up and down.

Another old trick is to intentionally wire one speaker out of phase, and place the speakers face to face.

This way the racket is reduced significantly as they cancel each other out, and you can leave them going in a spare room for a few days to get some hours on them.