Speaker sensitivities are based on how loud the sound would be 1 meter away with an input of 1 watt. For example, the M80s, measured in an anechoic chamber, yielded 91dBs(a quite loud sound)for the 1 watt of input. To get an increase of 3dB in sound level takes twice the power, so if instead of 91dB a speaker had a sensitivity of 88dB, it would need 2 watts to produce the 91dB level. Thus the M80 would need only half the power that the 88dB speaker would need to produce any given sound level and an amplifier only half as powerful to output whatever a brief peak(e.g. 110dB)would need.
