Which speaker system? Can you supply a photo?
Do you have technical specs for the drivers?

RS4
http://www.bobbyshred.com/infinity/Infinity_RS-4B.html

These are polypropylene drivers with foam surrounds. Unless you've abused them
by driving them at excessively high levels, the most-likely thing wrong is
that the foam has gone bad.

These are probably very good speakers (I owned RS-4.5s and have kicked myself
a hundred times over for selling them) and are worth repairing. I'm sure
someone can refer you to a source of replacement surrounds.

There is a problem (of course). Hardly anything sticks to polypropylene, and
you'll need an appropriate adhesive.