There wasn't an amplifier lying in the street too was there? That left hand speaker definitely looks as if the amplifier suffered an output transistor failure. The output pegging to the 60-80V supply rail would account for the distorted suspension (voice coil jamming at the end of the magnetic gap), the open voice coil, and the exploded 50V cap. The o/c on the other speaker was probably abuse at the same time.
I suspect that the timeline was something like this... Volume cranked all the way up, amplifier overheated at high power, excessive power blew one speaker, then the output stage of the other channel blew, with the catastrophic damage to the left hand speaker.
Something tells me the parents were away!