In audio, RMS can be used to represent two different things. One is a speaker or amplifier's peak power rating, where, for example, a speaker rated at 150 watts RMS can safely handle a 150-watt ...

Just because one is measured from 40Hz - 20KHz does not mean it will not produce frequencies below 40Hz. They rate the amp at this limited bandwidth to give the illusion of more RMS power as RMS power ...