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Ron H said:Just to nitpick - RMS power is technically a meaningless term. See Why there is no such thing as 'RMS watts' or 'watts RMS' and never has been.
He's not the only guy to say this. I had never even thought about it until one of my engineer colleagues at work made the same statement. He had the fact hammered into his head many years ago by a college professor. If you want more evidence, do a Google search for "rms power meaningless" (without the quotes).Nigel Goodwin said:Ron H said:Just to nitpick - RMS power is technically a meaningless term. See Why there is no such thing as 'RMS watts' or 'watts RMS' and never has been.
I think he's talking a load of rubbish!. As HiFi magazines usually do.
RMS power is the only decent way to report amplifier specification, mainly because it's very easily done and can easily be checked.
To qualify it a bit more, it shouldn't just say '60 Watts RMS', although even like that it's more comparable than any other specification. What it should say is '60 Watts RMS, continuous power into 8 ohms, both (or all) channels driven at less than 0.006% distortion' - this is actually the spec from my old Kenwood amplifier.
Ron H said:He's not the only guy to say this. I had never even thought about it until one of my engineer colleagues at work made the same statement. He had the fact hammered into his head many years ago by a college professor. If you want more evidence, do a Google search for "rms power meaningless" (without the quotes).
The point is, RMS power really refers to the average power dissipated by a resistive load which is driven by a given RMS voltage (or current). If you use the term literally, as in "the square root of the mean of the square of the instantaneous power", then you get a meaningless answer. For example, I ran a little sim on SwitcherCAD III (Linear Technology's free Spice-based simulator) in which a 1 volt peak sine wave drove a 1 ohm resistor. The average power is 0.5 watts, which SWCAD reports correctly. SWCAD will also dutifully calculate the RMS value of the instantaneous power (which is a double-freq sine wave with the +peak at 1w and the -peak at 0w) as being ~611mw. What does this mean? Nothing.
While I agree that this is basically a semantic argument, the definition above is actually the definition of average power. Why do we need two names for the same thing? Ok, I know, we have two (or more) names for lots of things.'RMS Watts' is defined as "the value giving the same heating effect as the equivalent DC power".
Ron H said:While I agree that this is basically a semantic argument, the definition above is actually the definition of average power. Why do we need two names for the same thing? Ok, I know, we have two (or more) names for lots of things.
I didn't mean to leave the impression that I didn't know how to calculate sinewave average power. I was simply illustrating that, if you apply the RMS operation to instantaneous power, you get the wrong answer.
Styx said:Err true VA (or Volt-Amps) and Watts are the same units.
Painandsuffering said:Really quick question... Why can't he just convert watts rms to watts peak which is as simple as multiplying his watts rms by 1.414 or dividing his watts rms by .707
pike said:When i took it home to test it out, i found out it was 300 watts RMS at 10% THD. you heard right 10% THD !!!