Understanding Amplifier Power Ratings

Take a look at advertised specs for power amplifiers and tell me what you see.

I already know, actually. You see lots of gigantic numbers. 2000 watts, 3000 watts, and on and on. If it seems too good to be true, well it probably is. To select the best amplifier for your purpose, you must understand the different Power Ratings that are advertised. More than anything, this comes down to learning the difference between a Peak Power Rating and a RMS Power Rating. Keep reading for a simple explanation that will insure you pick the right amp for your speakers.

Let’s establish what a Peak Power Rating is, first. Typically, Peak Power is defined as the full amount of power an amplifier can withstand for an instant before damage occurs. Essentially, it is the breaking point of the system. That seems fairly cut-and-dry, I know. It isn’t, though. There is a second measurement that can have a huge effect on this number and lead to highly inflated claims of power handling. Total Harmonic Distortion measures how much clipping is present in an audio system, in this case just in the power amplifier. The amount of THD, or clipping, allowed is determined by the manufacturer. Two identical amplifiers can be measured the same way, except for the amount of THD allowed, and the results will be completely different. The more THD allowed, the larger the Peak Power Rating number becomes. All this goes to say that advertised Peak Power Ratings are mostly arbitrary and generally useless in determining the actual strength of power amplifier.

That leaves us with the RMS Power Rating. Unlike Peak Power Rating, the process for determining an RMS Power Rating is mandated by the Federal Trade Commission. When you compare RMS Power Ratings from one amplifier to the next, it is much more likely that you are comparing apples to apples. Peak Power Ratings are usually apples to oranges. RMS stands for Root Mean Square, a mathematical term for how this number is derived.  Check out the graph below:

PeakvsRMS-640x395

This is a graphic representation of a sine wave, like the one mandated by the FTC for amplifier testing. The green line is zero, the red line is RMS, and the top of the graph is the peak. This can allow you to visualize the relationship between the three. The RMS is a higher value than the average between zero and the peak.

Back in the real world, this mathematical equation provides us with the RMS Power Rating.  This is a measure of how much power an amplifier can provide continuously for long periods of time. Now, we’ve arrived at the simple explanation. When choosing an amplifier, use the RMS Power Rating to match amplifiers with speakers. Other ratings are arbitrary, as well as model numbers using a Peak Power Rating. Beware of advertising tricks. That BigAmp5000 will never provide 5000 watts of power to your speakers. Except perhaps in the last instant before it catches fire.

Would you like to learn more? Ask questions in the comments. Would you like to know which Seismic Audio amplifier will match your speakers? Give us a call at (877) 347-6423. We’re here to help.

3 thoughts on “Understanding Amplifier Power Ratings

  1. You seem to allude, but not specifically state, that to match speakers to am amp, the speaker’s average power handling should equal the RMS output of the amp?

    Liked by 1 person

    1. That is true, essentially. Matching the speaker RMS with the amplifier RMS is not wrong. You do, however, have the lattitude to go up to 1.5 times the RMS rating of your speakers with your amp. So, you’d be perfectly fine with a 300w RMS amp pushing a 200w RMS speaker.

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