RMS vs. PMPO: The Output Power Rating Mystery

When it comes to buying a piece of audio equipment (an amplifier or an amp-speaker combination), sometimes brands try to use the term ‘PMPO’ to project the ‘Power Handling Capacity’ of their product. This is especially very misleading for a novice customer who perceives that, this projected higher number ensures loudness and quality. So, let’s burst this myth in a simple way.

Adding the words “1000 watts PMPO” on the package, the company is making the claim that this product can deliver 1000 watts of power. But there is absolutely no benchmark for measuring PMPO, and amps that make PMPO claims may only be able to hit that peak for about a second or less.

The industry standard is Watts RMS, and you should be searching for the RMS value whenever buying any audio equipment. If there’s no RMS measurement given, don’t even think about it, that’s junk! RMS is the possible best way to measure an AC Waveform. It’s the average power of a wave, computed over the entire cycle of the wave. RMS is measured with a sine wave and at the point where the amp is distorting the waveform by 10%. Waveforms can distort because the peak voltage is too high for the equipment, or because the sustained power is too much for the power supply. Either way, you need a sustained, continuous output for that to be a valid measurement.

So how do the PMPO people measure power? A single wave is just pushed through the amp and checked for the highest peak they can get out of it. They don’t mind about the distortion or whether that level can be sustained before the equipment is damaged. One single peak is enough. But it is not a valid measurement of continuous musical power. You will not be getting 1000 watts for the entire song, just a single peak for a millisecond or less. In reality, some amplifiers marked as 1000 watts PMPO will only have a true RMS output of 10 watts or less. Surprised?

So, remember that PMPO is a falsehood at the lowest and a worthless number at the highest!