PMPO is a marketing farce that falsely represents the power rating of an amplifier or speaker. It means Peak Music Power Output.
Real power is measured with a sine-wave in continuous RMS watts at a low distortion at or slightly below clipping, over the entire 20Hz to 20kHz range of our hearing. The power rating of good speakers say the duration of the test. Some woofers can survive for hours. Tweeters are rated in milli-seconds.
The "peak" of the waveform has twice the amount of power. The peak-to-peak of the waveform has 4 times the power of RMS power.
"Music" sometimes has full power for only a moment before the power supply voltage sags or before the transistors overheat. The PMPO test measurement is for only a moment.
Usually the output is mesured with the volume turned up way too high so the distortion is also way too high, doubling the output power.
The resulting false power number is then multiplied by the squared age of your grandmother.