Allisons are sweet.
you can repair a tear with nylon stocking, and rubber cement.
But if you want to get serious, take it to a re-cone center, where they repair professional speakers. http://www.speakerrepair.com/
A local music store can help you find a speaker repair person technician.
Most often, people want the foam surround of the speaker replaced. This is the outer ring of the speaker, that sometimes rots away or breaks...
Speaker shops can replace that, for just a bit of cash. Many times, it will make the speaker work OK again.
If one of your speaker cones has a tear in it, then i would suggest completely replacing the cone. From what I have quickly looked at, cone replacement parts and kits are fairly inexpensive. For Allison's Cone replacement parts and kits range from about $25-50. Like they've mentioned above, a tear in the cone will absolutely change the sound of your speakers. Check online for tutorials on Allison Cone replacement. It is fairly easy to do and they will sound as if they are back in original condition.