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?? 😁

erik_squires

I have recently been playing with speaker cables on my tube amp system (PM EVO 400 pre and power feeding Klipsch Cornwall 4's) and have found that the choice of speaker wire gauge has large effects on perceived volume and "control." There is nothing new here,of course, but it is fun to experiment with the so called "Western Electric" multi-stranded tinned copper wire. From 16 gauge to 10 gauge there is room for lots of slants on the sound emerging from the speakers. Since the Cornwalls are bi-wireable there is also room to play with mixing wire gauges between the bass taps and the treble taps too.

Have also been experimenting with ziploc baggies filled with powdered Rochelle salt wrapped around speaker cables. This is based on a comment Caelin Gabriel of Shunyata once made about these salts being good at attenuating ambient electromagnetic noise,

 

Usually an increase by 3db is doubling the spl , so raising by 10 db is kinda triple the spl and Watts is what you feed the speaker depending on sensitivity of the speaker. But you all know this by now 😁

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. 

I really did just want to ask, how can we tell what twice as loud is? I mean, I think I can, and it happens to match 10 dB.

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