If the tears are not in the foam surrounds, you can fix them with plain old Bounty and Elmers glue. Tear (not cut) bits of towel larger than the damaged areas, coat in glue, and apply with fingers, smoothing as you go. Touch up with flat black spraypaint when dry, if you care to. If it's the foam surrounds that are going, surrounds can be had for a buck or so, and there are tutorials on Youtube for the procedure. Rattling or buzzy speakers- look at the surrounds first.