PMPO is a spec acronym that can mean 2 things, Peak Music Power Output in speakers or Peak Momentary Power Output in amplifiers. PMPO is written as watts and it is the maximum power that an amp can output or that a speaker can handle over short bursts, usually milliseconds.
The two cannot be used interchangerbly as they have different meanings.
There is no standard definition for PMPO and due to this, the PMPO value can be taken from one maximum power burst/peak or the average of the highest power bursts. It all depends on what the manufacturer specifies it to be.
Is PMPO reliable?
The short answer is, NO.
PMPO ratings are basically marketing ploys. Manufacturers do this to make their product seem more powerful than they are and, in most cases, these measurements are taken in perfect and controlled conditions to achieve the highest possible value.
This is done in an attempt to make their products look more powerful than their competitors’ in the hopes that you will buy their products based on big wattage numbers alone (more=better analogy).
You will often see speakers rated as “600W PMPO” or “1000W PMPO” but in reality, this is not sustainable. It also does not take into account that the speakers have electrical, thermal, and mechanical limits. Most power drawn by the speaker is converted into heat other than sound.
Even amplifiers cannot sustain their peak momentary power output rating over long periods without damage. This power can only be maintained over a very short period of time, probably a few milliseconds.
But the worst bit of this is that some consumers may fall for this advertising strategy as the thought of having a very powerful speaker or amplifier for “earth-shattering sound” may be too good to let go of. This will, however, add no value to your home theater’s audio.
RMS vs PMPO
RMS stands for Root Mean Square and is a more mathematically accurate measurement of wattage in amplifiers and speakers. It is used to show how much power a product can output without clipping or failure by plotting different points of a sine wave over a longer period.
This is different from PMPO which is sometimes calculated by taking the real power value and multiplying it by a certain number. In simple terms, real power * X where X can be a random number.
To get the root mean square, all the plotted values are squared, then the mean of the squared values is calculated after which the square root of the mean is found. The testing methods can vary from one manufacturer to another.
In some cases, a manufacturer can find the PMPO value by taking the supply voltage and multiplying it by peak instantaneous Short-circuit current. Both calculations are absurd, exaggerated, and will not give you an accurate representation of a product’s power.
Notably, the PMPO value can be 3 to 10 times bigger than the RMS value and therefore, RMS is a better way to judge the quality of audio equipment for your home theater.
How to convert RMS value to watts
1 watt is equal to 0.707 RMS and this would mean that 1 RMS is equal to 1.414 watts. Therefore, if your equipment is rated as 50 RMS, you would take the RMS value, in this case, 50 and multiply it by 1.414 watts which would give you continuous power of 70.72 watts.
This would mean that the product can output 70 watts continuously over an extended period without failure/damage or causing distortion. Therefore, the continous power rating, in this case, will be 70 Watts.
But you should keep in mind there is no such thing as “RMS power.”
You cannot judge the power and quality of an amplifier or speaker by using the PMPO rating as this is a complete marketing gimmick to make the products more powerful. This rating is often associated with low-quality audio equipment.
PMPO will tell you nothing about the sound quality and is a value rarely used by serious Hi-Fi systems manufacturers.