Our 15 month old recently pushed in the cone on my wife's Tannoy speakers. We knew it was going to happen but my wife had thrown away the covers 6-8 years ago.
After a bit of googling, I tried using the pencil and sticky tape method, but no dice.
I tried using a straw to suck the cone gently out. Still no movement.
I decided it was time to try the dyson hose with no attachments. I gradually moved the hose closer and closer to the cone until I could see it vibrate then it just popped perfectly back into place.
Needless to say, the Tannoy's have now been moved into the loft and replaced by my cheapo Mission 760s. They still sound great to my untrained ear - I had forgotten how much bass the little speakers deliver.