To repair a damaged sub:
If a small tear or hole, just flip the sub over on it's face, and smear a little dab of silicone glue (or other handy glue, not super glue here though) on the rear side of the cone and realign the tear.
Let it cure for a few hours in open air, (room temperature)then carefully reinstall the sub. Pre-drilling the screw holes with a small pilot hole is best.
If you have a large tear or hole, may need to add some patching material (masking tape or cloth tape) to reconstruct the tear, then add some wood glue, over the tape and let dry. A hair dryer will help to set the glue quickly, then air dry for several hours, before installing the sub. If the damage is very severe, then a recone or new surround is recommended, if not dumping the sub, and getting a new one.
Recones are not cheap! If a replacement sub costs less than ~$80.00, go for that route. However, if you have a very expensive sub, or have a matched set, then a recone makes sense. Figure about $60-80.00 for a recone plus S&H and allow 2-3 weeks for the repair and return. Best to have the factory do this one... to insure it is up to factory specs when the recone is completed.
If you need new surrounds only, they can de sent out or order your own kit, and perform the work yourself. New surround kits are about $30.00 for a pair of subs. Just make sure you get a surround that matches your present ones.
Swez