"rms" = ?

[DBfan187 5,000+ posts]

and remember this is only near full volume with 0dB test tones. With music you more than likely will never get that kind of power out of the amp because music is dynamic.

 

[jmanpc 5,000+ posts]

Remove the words "Peak" or "Max" from your amplifier dictionary. They're pretty useless.

 

[bose301s 5,000+ posts]

RMS = 0.707
Willkas, Here is something you can read to help you understand what RMS stands for

http://www.opamp-electronics.com/tutorials/measurements_of_ac_magnitude_2_01_03.htm

Actually RMS is .707 of the peak in a sinusoid wave form. It is different for different wave forms however.

 

[Mass Car Audio 10+ year member]

Actually RMS is .707 of the peak in a sinusoid wave form. It is different for different wave forms however.

yes i know that a square and a triangle waveform have different measurements. But do you ever listen to a square or triangle waveform in your car ? no.... So there is no point of using the other measurements when measuring the output of a car amplifier. So for car audio terms it is 0.707

 

[bose301s 5,000+ posts]

yes i know that a square and a triangle waveform have different measurements. But do you ever listen to a square or triangle waveform in your car ? no.... So there is no point of using the other measurements when measuring the output of a car amplifier. So for car audio terms it is 0.707

Well, you never actually listen to a true sine wave either, so even then the .707 doesn't apply.

 

[Mass Car Audio 10+ year member]

Well, you never actually listen to a true sine wave either, so even then the .707 doesn't apply.

When testing the output power of an amplifier you use a clean 60hz or 100hz swine wave. How can you say it doesn't apply ?

 

[terra 5,000+ posts]

When testing the output power of an amplifier you use a clean 60hz or 100hz swine wave. How can you say it doesn't apply ?

Because we're not discussing testing output using sine waves. We're talking about dynamic music output..

 

[Mass Car Audio 10+ year member]

Because we're not discussing testing output using sine waves. We're talking about dynamic music output..

Ok then, What measurement for RMS do you use for dynamic music output ? I'm pretty sure it's still .707

 

[JimJ 5,000+ posts]

Remove the words "Peak" or "Max" from your amplifier dictionary. They're pretty useless.

For audio //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[ciaonzo 5,000+ posts]

Just wanted to put it out there that we actually do listen to sine waves sometimes. Any time you are listening to a bass disc like Bass Mekanik or DJ Billy E, etc., those are true sine waves.

Thought I might also add this for an alternative view, it's an excerpt from the link below.

Let us assume a sine wave input signal. The way the amplifier power is measured is to use a nominated load, and then to wind up the volume control until the output is just below the point at which it begins to distort significantly (according to some agreed and stated distortion measure, though this is not critical in practice). The average output power over many sine wave cycles is then measured. This is defined as the time integral of the instantaneous power over the measured time, divided by that time (which is always taken to be very large).

 

In simpler words, it is a straight average or mean of the output power, measured over a long time, and has a real technical significance (e.g. it measures the heating power of the amplifier).

 

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. This could be done, but it is not the power as measured, and furthermore, it would have no technical significance (e.g. it doesn't measure heating power).

 

The confusion in terminology comes because the nominated amplifier load for the measurement is nearly always purely resistive. For this case (only),the measured average power is proportional to the MS [mean square--ed] current or voltage (not RMS) or is (exactly) equal to RMS current times RMS voltage. But it is not the RMS power! There are several other power measures that are important with amplifiers (e.g. transient power measurements) but they shouldn't be used unless both writer and reader are clear about them.

http://www.hifi-writer.com/he/misc/rmspower.htm

 

[n2audio 5,000+ posts]

Well, you never actually listen to a true sine wave either, so even then the .707 doesn't apply.

When testing the output power of an amplifier you use a clean 60hz or 100hz swine wave. How can you say it doesn't apply ?

It doesn't apply because a standard DMM already reads RMS voltage.

Check wall voltage - its peak is about 170v, but we call it 120 since that's the RMS. Your meter will read 120.

And taking .707 of a given audio component's peak power rating isn't useful either. Car Audio mfg's have managed to do away with ANY sort of universal definition (forget about scientific) of peak/max power. It's just a number the marketing dept. thought they could sell.

 

[Mass Car Audio 10+ year member]

It doesn't apply because a standard DMM already reads RMS voltage.
Check wall voltage - its peak is about 170v, but we call it 120 since that's the RMS. Your meter will read 120.

And taking .707 of a given audio component's peak power rating isn't useful either. Car Audio mfg's have managed to do away with ANY sort of universal definition (forget about scientific) of peak/max power. It's just a number the marketing dept. thought they could sell.

I use a oscilloscope not a DMM to test output power because it is more accurate. So i actually see the full wave on the graph.

 

[soldiermedic 10+ year member]

Wow...um...did the original question get answered? LOL