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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
fleschler
2,021 posts
 

In 55 years, I've never blown a tweeter or speaker.  I've used 16 watt Sherwood S7100 receiver to 200/400 watt hybrid Counterpoint amps.  Electrostats and dynamic speakers.   My 35 watt voltage regulated highly modified Dynaco ST70 lacks the watts to really exploit my Legacy Focus 6-12" woofers and provide ultra resolving sound as my 125 watt custom monoblocks but they have the same sound signature.  It takes a lot of watts to increase 3db of sound, especially for low impedance, inefficient speakers.  I match the amp to the speaker and don't worry about loudness (my current listening rooms can go above 110db clean and easily but that's more than I want or need).  

emergingsoul
1,182 posts
 

It’s all about Appalachian mountains versus the Rocky Mountains when it comes to frequency definition.

The ability of ears to differentiate between all those pressures circulating via sound waves, or pressure amplitudes, is truly remarkable. So the more precise those waves can be transferred from speakers the better it should sound.  And somehow higher wattage delivered through higher quality amplifiers is really helpful and so difficult to explain.  I guess a lot has to do with how quick an amplifier responds to all those frequencies in terms of making sure that all the power demands are spread to reproduce all those frequencies in an incredibly fast manner with very low distortion.

fleschler
2,021 posts
 

Someone on Audiogon posted about an ASR review of a 10 watt Luxman tube amp by Amir. He used an inefficient speaker to test how it sounded. What a joke. Three ASR posters Ken Tajalli said the Luxman tested as defective and should have been returned/testing was unreliable. Robaroni said the amp is pleasant to listen to DonDish and Robaroni seconded my opinion that Amir should have used an efficient speaker as this is a low power amp which it was made for. So, matching a working condition amp to a speaker is foremost to truly hearing the amp as well as speaker. (Amir said it is ALL in the bench test results-this time of a defective amp-ha ha).

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