I had the same thing happen but tape didn't work. I read a thread that recommended putting your lips around the tweeter and sucking. I know it sounds a little corny, but it worked. Hope this helps.
Tweeter cone on my B&W 805 Naut's is pushed in
I bought these used and the buyer didn't indicate that one of the tweeter cones (not the grill) was pushed in. It isn't broken or torn, but clearly somebody touched it and pushed it in. My question is how significant is this damage. The speakers sound good, but I can't imagine that this isn't causing some loss of performance.