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What is RMS?


Gadgeter
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The words 'watts RMS' is intended to show the continuous average power output of an amplifier measured using the correct test signal (a sine wave) in accordance with US standard guidelines; the correct period of time for measurement (more than five minutes), a properly calibrated, true RMS-reading voltmeter with an accuracy of better than 1% of reading, without exceeding a specific level of distortion (0.1%) into a defined load (usually 8-ohms) with the amplifier first having been pre-conditioned by means of driving all channels simultaneously with a 1kHz sinusoidal signal to a nominal power output into the rated load equal to 33% of the rated power output for at least hour (or more if protective circuitry interfered with continuous operation).

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Hi Bro Vic,

welcome to mycarforum. Nice to see you here.

 

As for your Pioneer HU, MOSFET 50w x 4 from what I understand, the average RMS for those MOSFET 50w is producing between 25w RMS to 27w RMS per channel. So 50w is just peak power. Hope this helps.

 

How about coming for the Nasi Padang ICE meetup Wednesday night. You can get lots of help from those ICE kakis there.

 

by the way, are such HU good enough to drive a pair of lanzer heritage coaxial speakers?

specs of the speakers are 140W RMS. Peak is 280 RMS.

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If only the peak value is indicated, RMS value is always at 70% of the peak.

 

I think the peak power from an ideal sine wave input should be exactly twice the "RMS" power. "RMS" power is generally a misnomer, referring to average power, which is half the peak power when sine waves are involved. The reason the root-mean-square comes into the picture is when voltage or current is considered. The RMS voltage of a sine wave with a peak voltage of V is V/sqrt(2), which is about 70% of V (this is from basic integral calculus). But the average power (wrongly called "RMS" power) is still half the peak power because power dissipated by a simple resistive load is given by: P = (V^2)/R, so average P = (V/sqrt(2))^2/R = 0.5*peak P.

Edited by Turboflat4
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Hi Every one

For the geeks in the crowd, what follows is a technical description of what RMS means and how to compute it. If you are not technically inclined, then be warned that you may require counseling to return to normalcy, if you read further. Those who slept through less than 50% of high school algebra should be able to follow.

 

 

Edited by Tinahogard
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RMS is a computer term

___________________

Reinaldo

 

No it isn't.

 

Root-mean-square is a statistical (mathematical) operation that has wide applications in statistics, probability theory (esp. random walks and other Markov processes), electrical engineering and other fields. Definitely not limited to, and not even especially important in, computer science.

 

E.g. the usual standard deviation calculation used in statistics is an RMS = You take the square root of the mean of the squares of data values.

 

RMS voltage and current are just the same term being used in the context of A.C. (Alternating Current) sources. RMS voltage and current follow the usual statistical definition.

 

"RMS power" is a misnomer because (as I've mentioned before), when people use this term, they're most commonly referring to average (mean) power.

Edited by Turboflat4
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Neutral Newbie

Okay! I stand corrected. Yeah! you're right. In computer RMS is Remote Monitoring Systems but we're talking about automotive here. I'm integrating computer programs into my car that is why I thought it is computer term.

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