possible new material to fix cracked subs/ maybe a sound deadener?

I have this stuff called PlastiDip, its a rubbercoating that you spray on to the handles of tools for more grip , i use it to spray onto the pistol grips of my rifles and its held up pretty well. This guy sprayed an entire car with it for paint i'm not sure if it would work to fix cracks or something in a sub its the same stuff as that flex seal stuff, two or three apllications gives you about 2mm thick of rubber. Any thoughts? http://www.youtube.com/watch?v=rNY9Dx617N8

I'd try it! I mean if the the woofer is going to be garbage anyway... The other option which just saved me is to put in new cones and foam. Now I am a real novice to this stuff but I could not find replacement speakers for the Nakamichis which had gone south in my classic car and sound system. So I bought a speaker foam replacement kit off the net and put in last weekend. The speakers are like new! Sound great!!! You can also buy new cones I believe from these companies, which might be a bit trickier to install but... well my repair cost me $25 and a couple of hours (waiting for glue to dry mostly). New speakers as good as the Nakamichis would have been around $500. Simple decision for me!

There's the problem... it's rubber. It might work for cracked rubber surrounds, but not for the cone itself

I would agree, replace the cone and be done with it. Good luck!