I was trying to figure out why the subwoofer I've had since college (my trusty YST-SW50) suddenly developed a rattle while watching Babylon 5. Turns out the foam that insulates the control-facing chamber fell out, and the one for the terminal-facing chamber deteriorated. So with a little ingenuity I think I've isolated and fixed the problem.

Here's hoping for many more years of problem-free listening from this sub.