A 10db increase in SPL is typically perceived as "twice as loud". This usually requires a 10X increase of amplifier watts. So an 80 watt amp can have a SPL 10db higher before clipping than an 8 watt 300B SE amp.
Perception and Watts: Doubling of power
There's a curious rule of thumb, which to my ears seems mostly true:
- To double the perceived volume, you must output 10x more power.
10x power = 10 dB by the way. We've read this as we were buying amps and trying to decide between 100w/channel and 150w/channel. We are told, repeatedly that 50 W difference isn't really that much.
On more than one occasion I've tested this and found it's pretty much spot on. Here's my question:
How can any of us really tell what half as loud, or twice as loud is?
I mean, think about this for a bit. I cannot tell half as bright, or twice as bright, but it seems I actually CAN tell what half as loud is. How does this even begin to work in the ear/brain mechanism?? 😁
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Hi Erik, twice the volume, i.e. twice as much sound pressure level, is 6dB(spl). And this requires 4x the power in watts. It seems that 10dB is what most of us perceive as double sound intensity, i.e. from a psychoacoustic point of view. And even then, our perception is affected by the frequency. The lower the frequency, the lower our sensitivity, so +10dB may not be enough in the bass, for example... Interesting stuff! |
@iseland I think you mean an increase by 3db requires double the power (or watts) Certainly this is not a tripling of average SPL |
Back in the day we found that more speakers (specicially: tweeters) got killed by too SMALL amp that were clipping like crazy when playing louder, and the clipping sent huge amounts of watts to the tweeter. Most tweeters blow at 10W (just throwing a number at it), so a 20watt amp is capable of killing a tweeter (if sending a lot of high frequency clipping noise to the tweeter). |
Couple of things come to mind. When you buy an amp w twice the rated power, the power supply in that amp is generally much bigger than in the smaller one. As was mentioned in a post above, a bigger amp playing at the same volume as a smaller amp will sound more dynamic - provided they are built to the same quality level. I tend to believe this difference is connected to the size of the power supply, more so than the power (watt) capability of the amp. The Hiraga Super 30 watt class A amp I built, has 192K uF in the PS, with a 500VA transformer. People build these amps with insane amounts of capacitance, but for this built, I went with this. Next time I build this amp, I’ll be building it as a dual mono design with greater capacitance in the storage so I can hear first hand how that translates into real world listening experience. I recently built a single ended EL84 based amp. It’s about 3 watts. Love the sound, but want a bit more usable volume. So I’m about to built a single ended EL34 based amp that will get me approximately 6 watts. Double the power. Different tubes and circuit design, I know, but I’m just curious how that 6 watts will present compared to 3 watts. 3 watts don’t mean a hill of beans if your amp is pushing 200watts into the speakers, but going from 3 to 6 is doubling the power. Thankfully, going from 3 to 6 watts is a heck of a lot less expensive than going from 150 to 300 watts :) |
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