RMS Power?

Hi Roger,

All of us, certainly including Kijanki who is very knowledgeable technically, completely understand and are in complete agreement about the technical aspects of what is being discussed, i.e., the "basic electronics" and the math you referred to.

What he is going on about is simply the terminology that is being used.

And his point is that strictly speaking what the words "RMS power" literally mean is the RMS value of a waveform that defines how power varies as a function of time. Which would be 141.4 watts in your example, while of course 100 watts (the product of RMS voltage and RMS current) is what is actually being referred to when that phrase is used.

Regards,
-- Al

@kijanki  Al, leave it (he is not going to get it).

Thats really rude, however

Would you please be so kind as to supply a link to what you want me to read, there are several articles on Wicki. 

OH, dont worry, I will get it or apologize for not getting it. 

@almarg  And his point is that strictly speaking what the words "RMS power" literally mean is the RMS value of a waveform that defines how power varies as a function of time. Which would be 141.4 watts in your example, while of course 100 watts (the product of RMS voltage and RMS current) is what is actually being referred to when that phrase is used.

First when someone starts an OP with "there is no such thing as RMS power" whats that mean?

RMS Power doesn't vary as a function of time, instaneous power does. 

Im still waiting for the link to Wickipedia. Do you have it. Im just on pins and needles here.

Hi Roger,

I found the Wikipedia page from which Kijanki quoted (the link opens near the paragraph he quoted):

https://en.wikipedia.org/wiki/Audio_power#Continuous_power_and_%22RMS_power%22

RMS Power doesn’t vary as a function of time, instaneous power does.

To be sure it’s clear, I absolutely did not say that "RMS power" varies as a function of time, although I can see how my statement might have been misread. I said that...

... what the words "RMS power" literally mean is the RMS value of a waveform that defines how power varies as a function of time.

(The "waveform defines how power varies as a function of time"; the RMS value of that waveform of course does not define how power varies as a function of time).

Again, what Kijanki has been addressing is terminology, nothing more.

Regards,
-- Al

@kijanki @almarg

Like to make it hard done you. I looked at all the references listed in the Wicki article. They can easily be clicked on above.

Half of them are referring to average power as a speaker sees it so as not to overheat the voice coil. That is indeed time averaged and all is well there.

However a speaker is not an amplifier. If you are betting on reference #8 being valid I will take $100 on that bet. Its pure fiction. http://www.hifi-writer.com/he/misc/rmspower.htm

Besides the admission at the top Most of what follows is an edited version of an email sent to me in April 2003 by the editor of Australian HI-FI. It was so well expressed I want to see it published, somewhere. So here it is.

Unfortunately the precise authorship has been lost due to rigorous cleaning of computer archives and trashed hard disks. I am told that much of it was probably from ’an electronics professor at Uni of NSW’, originally written as a letter to The Guide, an insert into The Age newspaper. Should the lost electronics professor seek to claim authorship (or even banish his words from this site), I would plead with him or her to email me at scdawson (at) hifi-writer.com.

Do you agree with this statement... By contrast, RMS (root mean square) power, would have to be defined as the square root of the time average of the square of the instantaneous power, since this is what ’RMS’ means.

FIrst thing wrong with that sentence is that if you take the square root of something you squared you get the same thing back. And what is the square of the instantenous power anyway.

Could a math major please come help us out. This is getting no where.

Though I love and contribute often to Wickipedia this article needs a lot of help. Did you not read the banner at the top of the article..

This article has multiple issues. Please help improve it or discuss these issues on the talk page. (Learn how and when to remove these template messages)This article may require cleanup to meet Wikipedia’s quality standards. (June 2011)This article possibly contains original research. (October 2008)

Please read this also. https://en.wikipedia.org/wiki/Talk:Audio_power

This is a "start class" article, please read the following https://en.wikipedia.org/wiki/Wikipedia:Content_assessment

Evidently you guys have not vetted this article at all. Heres another complaint I found on the talk page..   

 One thing this article does poorly is differentiate between speaker and amp ratings. Both are given "RMS" and "PMPO" ratings, but the conditions are different. The peak power of an amps is directly limited by their voltage rails and the minimum impedance of the loudspeaker. It is impossible to have a higher peak instantaneous power than this (unless due to reactance?) But for loudspeakers, the peak instantaneous power is not as clearly defined, and has to do with destruction of the speaker. — Omegatron04:48, 25 October 2007 (UTC)