Have you ever wondered how that pair of speakers they are selling at the discount store for $10 can put out 120 watts of power? Well, depending on your definition of output power...they can...and it has fooled many people! I know people have told me that their home stereo unit has 2600 watts of power output...even though it is connected to a standard 120-volt power supply that is only allowed to draw 2000 watts before tripping the circuit breakers!
The answer to this issue lies in how they measure the output power of the device. Usually if you look at these huge numbers, you will see the letters "PMPO" underneath. PMPO stands for "Peak Music Power Output" or "Peak Momentary Power Output". Notice the word peak. The vendor of the product calculates PMPO based on the maximum power output of the device under perfect conditions and 100% efficiency. These conditions are impossible to obtain, and no device can sustain the PMPO power for any significant length of time without being ruined. The PMPO power relies on the fact that amplifiers can provide short bursts of very high power. Over time, these short bursts when averaged with the lower output powers, gives the real value.
The Real Power
Vendors use PMPO power to hide underpowered power supplies and amplifiers. When you see something with a PMPO measurement on it, turn it around and look at the specifications. Often, the input power from the AC mains is 5 or more times LESS than that of the PMPO power. You also may see a more accurate measurement, called RMS (Root Means Square) power and DIN power. These types of measurements average output over time, creating a much more reasonable reading. Don't be fooled by cheap products which appear to put out big power.
So, how do you find the RMS Power from the PMPO Power?
I have been asked this, and there is no single answer or mathematical formula to convert these values. The peak output of the amplifier is going to differ based upon the amplifier's design, and the type of sound that is being amplified. Often each electronics manufacturer will create their own proprietary formula for figuring PMPO power. Usually, the PMPO power is about five to ten times higher than the RMS Power.
There is NO mathematical formula that will convert PMPO to RMS values or vice-versa
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