Just use an Allen-key type wrench and unscrew the four bolts on the lower woofer, pop it out carefully, unclip the two leads to the woofer, and feel around inside the enclosure. You might have to remove both woofers and shine a light inside. It would likely be easier if you lay the M60 on its side while you grope around inside the enclosure.
Be sure and reconnect the clips to the woofer terminals before you re-install the woofer(s).
Axiom Resident Expert