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How Much Amplifier Power Do I Need?

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I have had this question asked so many times. I wrote an article to address this.


The article gets you an understanding of how amplifier power affects loudness (sound pressure level) at your listening position.



This calculator is also a very good tool to use to figure it out:




Edited by orchardaudio
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For the most part the article is correct from a general rule-of-thumb perspective.

Just a few things missing from the article. 😉


The size of the space your speakers are in.

A 10000 cubic foot room is going to require more acoustical power output from the speakers than a 2500 cubic foot room. This in turn will require more amplifier power all other things being equal.


How the room is treated, what it contains = how reflective or absorptive it is.


Doubling the listening distance doesn’t necessarily decrease SPL 6dB

Different speaker designs “throw” the sound differently. Line source array for instance do not decrease as rapidly with distance.

Some horn designs are specifically designed as near throw or long throw and fall off faster or more slowly in projected SPL with distance.


Room gain. Again, depending on the room size, contents, acoustical treatments and playback loudness level room, reflections can make it “sound louder” because reverberation time doesn’t decay as fast at higher SPL.

Room gain can contribute +10dB to apparent (perceived – sounds like) louder.


The type of music you listen to. Some music like classical typically have more dynamic range than say a recent loudness wars hard rock recording.

Peak levels are perceived much different than sustained levels at the same SPL.

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