[quote name='iiipopes' timestamp='1352759555' post='1867214']
It's not that a person is "more likely" to blow a speaker underpowered, but it can happen.
In a nutshell, it's this: when the amp is peaked out and can't deliver any more power, it clips the signal. These clips are, in essence, immediate DC going to the speakers. Because it is a clip, the ramp on the front side of the wave form is pretty steep compared to non-clipping signal. So one or both of two things can happen:
1) the speaker perceives an immediate jump in signal, and if it's too compliant, can blow its extension on the overshoot, and
2) DC means amperage, which means heat, which over time, if the speaker coil can't dissipate the heat, it will burn out the coil or disintegrate the coil form from the heat, or even kill the magnet (old Alnico speakers)
Most new speakers, especially musical instrument and reinforcment drivers, are designed to take at least some abuse. But the best bet is, going in, match everything so that the rated load of the speakers is at least the rated power ouput of the amp, if not more, and always watch the power amp to make sure it doesn't clip. Most modern amps have some sort of protection circuit or "soft clipping" circuit that also helps prevent too much DC from clipping from going to the speakers, and/or a thermal protection shutdown. And occasional "red" peaks are no big deal, but the amp should always be monitored visually to make sure it isn't constantly clipping, if for no other reason than the deterioration of the sound quality from the distortion.
[/quote]
There is no DC from a not broken amp. Doesn't work like that. Even if it did, dc doesn't break speakers, you can put a 9v battery across a speaker and it is fine.