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Can anyone explain to me (preferably in laymen terms) a formula to convert Watts (for say a car audio amp) to its RMS counterpart?
Did a google search to try and understand how to convert it but got more confused.
Cheers.
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If you are talking about PMPO (peak music power output) vs RMS there is no conversion factor.
With AC voltages, such as household AC, and also music coming from an amplifier, the voltage on the waveform has a + peak and a - peak. This is the peak voltage. Somewhat less than that is the RMS value, which is related to the area under the waveform curve. For example, US household AC is 120 Volts RMS. It is also 170 Volts Peak. With audio, the rating is in watts, rather than volts, and the watts that the amplifier will output depends on the impedance of the speakers, so it is not a simple thing to convert RMS watts to peak output. This is why the RMS rating is the only one you really need to know when evaluating an amplifier. However, Peak Power is a marketing term that usually is just double the RMS power, and PMPO is another marketing term that occasionally may be 4 times the RMS rating. For DC, the peak and RMS values are the same. -
Member
- Nov 2002
- Victoria, British Columbia, Canada
Craig is 100% correct but I'd also add:
RMS stands for Root Mean Square which basically is a statistical measure of the average. In the case of houshold AC the voltage flows in a sinusoidal wave. With a bit of math the relationship between peak and rms voltage is RMS = PEAK / (square root of 2) = PEAK / 1.414
As Craig states, for music there is no relationship - the waveform for the sound is pretty random. Some amplifiers will also state their "headroom" - a measure of peak power over short periods. I found the following which may be useful:
http://www.audiovideo101.com/dictionary/dictionary.asp?dictionaryid=246
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