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Power Ratings: What Do They Mean?

Power Ratings Choosing an Amplifier

I’ve noticed lately a lot of discussion about the idea of matching speaker and amplifier power ratings. RMS power. Peak power. What do these terms mean? How important are these ratings?

If you look in the manual for your speakers, you’ll see RMS power is typically 1/2 the Peak power rating. A lot of people mistakenly assume that bigger numbers on these ratings means the speaker will play louder.

RMS Power

There’s a general concensus that RMS power is the average amount of Watts a speaker can safely dissipate as heat over time. There is a standard called CEA 2031 that came about in 2006 that is supposed to mean any manufacturer conforming to this standard now has RMS power ratings that are comparable to another CEA 2031 compliant manufacturer’s speakers. However, since quite a lot of manufacturers don’t follow CEA 2031, there are still a lot of speakers that are rated using different methods. Commonly this varies between 1 W at 1 m or 2.83V at 1 m. See 1w/1m vs 2.83v for further information.

Peak Power

Peak power is one of the most useless ratings, whether it’s a speaker or an amplifier. Basically this figure is made up. Most often it appears to be RMS Power doubled. What’s worse is less reputable manufacturers will print these big numbers very prominently to make them more appealing. Have you ever seen a $20 pair of speakers rated for 250 Watts? How about a $200 3,000 Watt amplifier? Question it.

How Much Do Either Of These Ratings Matter?

Peak power can be ignored, but we need RMS power ratings, right?! The flaw with matching your amplifier to your speakers is that music is dynamic. Your 4 Ohm speakers will sometimes have a much higher resistance while music is playing. Higher resistance equals lower power output. Even if your voltage is stable, or the amplifier has a tightly regulated power supply, it’s seldom putting out the RMS power.

But the Speaker Power Ratings Say 150 Watts RMS. Don’t I Need a 150 Watt RMS Amplifier?

There comes a time when one has to ask the question, “How loud do I really need my music to be?” In a car with the windows up a true 150 Watts to each speaker is going to cause hearing damage. It gets even more complicated when we factor in the varying heat dissipation ability of the various sizes of speakers. 

Don’t Sweat The Numbers…

…to a point. Big power does have its place in car audio. Ask anyone who loves loud bass how happy they’d be with less power. Competition vehicles of all types may have many amplifiers with multiple thousands of Watts RMS altogether. For the average person who just wants more clarity from their stereo when they turn up the volume it’s more important to buy an amplifier based on the following criteria:

Choosing An Amplifier

  • Warranty/Dealer Support
  • Brand reputation
  • Will it fit where I want to install it?
  • Longevity/Reliability
  • Buy the most power you can afford after all other criteria have been decided

Alternate Criteria from the SPL Competitor / demo perspective, shared by James Metzger

Very first thing I look for (most wont know the difference) is am I looking for a Brazilian or Korean amplifier. They are both built very, very differently.

Next I look at is brand quality. Does it do rated power. (Good way to tell on smaller amplifiers is take the fuse rating x 14.4. It gives you a general idea of what power itll be around.)

Next is if I already have the woofers, is this amplifier stable at the wired impedance.

Lastly is what my electrical looks like. Do I have enough battery/alternator power for this amplifier.

Choosing Speakers

  • Fitment in your vehicle
  • Brand reputation
  • Warranty/Dealer Support
  • Budget
  • Listening impressions
  • Longevity/Reliability

Further Reading

Barry Schanz

3 thoughts on “Power Ratings: What Do They Mean?

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