If you mention to people that you have a power amp at home that runs at over 1000W, most of them will look at you wondering how you’re not suffering hearing loss.
While it’s not to say that everyone needs that much power (though for a subwoofer it’s great), here are the reasons it’s beneficial to go beyond the conservative power ratings a lot of basic amps provide.
First and foremost, dynamics.
In movies and music, audible peaks can be at least 10dB higher than other sound effects. Given that every 3dB increase requires twice the power to generate, that a 10dB peak demands almost 10x the power.
If your average/RMS power usage in that track is 20W, that peak could suddenly require 200W to play with impact — something the average stereo receiver would struggle to do.
What happens when the amp is not able to spike as high as the signal demands can be one of two things.
- Clipping, where the signal is squared off and can damage speakers, since it causes the cones to essentially pause for milliseconds instead of snapping back and forth, which can overheat the voice coils.
- Compression, where the signal may not clip per se, but that’s because the amp simply plays the loudest it can safely play. This means the audible difference between the rest of the sound effects and this peak isn’t as great as it should be, which gives the audio a duller, flatter sound. If you’ve listened to music or movies and felt that nothing had a real sense of impact, this may very well be why.
RMS and “Peak” Power Don’t Mean The Same In Amps Vs. Speakers
In speakers, RMS basically means the typical recommended amount of power they can handle continuously. Their “peak” power refers to what the voice coils can handle in short bursts, like those peaks mentioned above. The peak is generally 2-3x what the RMS rating is.
Although amps are often advertised with RMS and peak power ratings as well, most audio enthusiasts agree that amps can’t effectively operate beyond their RMS power rating.
Running a speaker at or beyond its RMS rating can be ok as long as the voice coil stays cool enough, and as long as the overall excursion isn’t bottoming out the cone. To a degree, a speaker is built for that.
Plenty of people have reported these results with speakers and subwoofers.
An amp starts to distort audibly at around 80% of its RMS power rating, and can clip and cause real issues when it exceeds the RMS rating. Unlike a speaker, driving an amp 2-3x over its RMS rating isn’t harmless and can sound terrible.
This is also why some people recommend matching your amp’s RMS power to the speaker’s peak power.
If you have a subwoofer capable of 1000W peaks, for instance, it can make sense to pair it with a 1000W RMS amp. This way, any loud peak in the track will always be within the safe limits of what the amp can put out, and there shouldn’t be much distortion or compression. And you’ll always be getting as much from your subwoofer as possible.
People mistake having a 1000W amp with playing at the 1000W level and stare wide-eyed at why that much volume is necessary. In a way, you could say that you have too much amp on purpose so that the range you will need is always at its best.
Because amps distort at 80% of their RMS power, it can also make sense to buy an amp even more powerful than your speaker since you know you won’t be cranking it up all the way.
For instance, a 1500W RMS amp with a 1000W speaker. The wattage difference will only matter with the amp turned all the way up, which it won’t be. The rest of the time it’s clean power — as much as the speaker is asking for.
Why Big Wattage Gains Aren’t As Crazy As They Seem Volume-Wise
1dB is the measurement of the smallest difference in sound volume our ears can distinctly hear.
For every 3dB increase in signal level, it requires 2x the amp power to play. 3dB translates to roughly a 25% increase in volume to our ears.
That means every time you want 25% more volume, you are doubling the power demands.
You can see how this can escalate quickly. By the time you’re at a movie volume level where the bass from explosions is using 250W, for instance, you’d be jumping immediately to 500W for that next 25% increase in loudness. If you wanted 50% more loudness than you have now, you’d need to go all the way to 1000W.
At a glance the difference between a 250W amp and a 1000W amp can seem gigantic, but in reality it might only mean 50% louder (and not 400% louder).