Back to the sub...
If I had to guess, I'd say the former is adhered to the cone at the top edge and inside/outside surface of the former. It would be kinda neat if it was threaded into a mount on the back of the cone like how metal pipes are threaded, but the former material would have to be a lot thicker for that I think. If DC got fancy, they could have it be a one piece cone/former made fully of CF, but god only knows what that would cost them.