As Nick as said many times, "speakers are dumb." They do what they are told. They have NO idea that there is a difference between a clipped signal and a clean signal. It just understands power. If you get them too hot.....well, just look at the pictures.

I think the maximum the amp can send when fully clipped is two times RMS for brief periods but when playing a whole song or something, the amp can't keep that amount of power up for the extended period so it may average out to be about 1.5 times RMS.

i am a bastard to subs, I scorch them by clipping the chit out of amps, and I bottom them hard cuz I am disgustingly obssessed with lows...

BUT...

I have NEVER seen anything like that sub... cooked ass cone! WTF! That had to be just the right amount of power to not cook it right away, yet get it hot enough for long enough to slow BROIL like that... thats just nutz. I love going ported, cuz if I make it get a little stinky, I smell it right away and back down.