First driver = speaker
Second its going to be a blown surround as it sill makes sound so the voice coil is at least still functional. Best bet would be a replacement driver. If there is a suitable replacement online if not then there's not a lot that can be done.
They are well known for having the foam on the sub woofer crumble into dust. Very poor quality on JBL's part. They sound great and are nice but die due to sub failure. I have 4 of them with the exact same problem. Work fine but sub foam deterioration. Working on re-foaming them.
If you're handy, you can do a really ghetto fix by using some sort of cloth or neoprene and rubber cement to keep it on the cone. This will keep it from sounding flappy and blown, but won't last forever. I've never done this with a sub, but I've done it with quite a few paper cone midbass woofers with decent results.
I miss $250 GPUs that could still play everything.