I have repaired torn speaker cones before, with Nail Polish (not mine, of course!
), to bridge the gap between the tears in the cone.
That used to work with older paper cones, but I've never tried it with the newer multi-chemical cones.
BTW, my G/Friend used to get really annoyed to apply her Nail Polish and there would be small paper fragments in it, I can't think where they came from, there must have been a "paper storm" while she had the bottle open!.