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

The there’s amps that can supposedly “increase instantaneous power, for effortless reproduction of musical transients.” Don’t know the science behind this, but it sounds like a good thing…

@anotherbob - Marketing hype for a couple of different things some amps do. There were some like NAD / Proton (back in the day) which famously used 2 voltage rails in the amps. The high voltage had no staying power, but for short transients could deliver more than the low voltage rails could do. I think this was Class H.

Bob Carver’s amps did something like this, using a linear amp which would float among multiple voltage rails. The NAD/Hypex hybrids do this also.

A lot of this has to do with federal regulations about how you rate a power amplifier. To combat outrageously useless amplifier specs of the day the FTS imposed regulations about not only stating distortion and power together but also your amp must be preheated. The preheating required a lot more heat sinks to achieve the same wattage rating. As a result, some amplifiers may have significant more headroom than they may show in the power spec alone.

To be honest, music is never steady state and a lot of audiophiles with 300 Watt amps never go beyond 30, so there’s a lot to be said about right sizing an amp to your needs. .

Forgot to mention why Alexa was screaming (we are getting one of these for Christmas).

 

DeKay

Erik:

The early NAD PE's used class G.

I demo'd a few of those integrated amps and SQ improved, IMO, when the Power Envelope circuitry was defeated.

Do the meters on your Luxman register "fast" peaks?

I had a Carver MXR-130 hooked up to single driver speakers (Stephens 80FR) and the meters showed them to be pulling quite a bit of power on musical peaks.

There are two meter settings (low/high) and it only showed up on one of the settings (forget which).

This said, I do not notice clipping/compression when running them with my 3 watt 2A3 amps, but I doubt that I ever listen louder than 80 dB (probably much lower, but with unknown peak levels).

 

DeKay

 

The early NAD PE's used class G.

Thanks for the correction, @dekay 

 

Do the meters on your Luxman register "fast" peaks?

 

Not a tall, I don't think of them as very twitchy.

Here's a blurb on meters.

I recall a few vintage pieces with fast/slow meter settings, but the Carver switch is marked low/high.

The Carver has not been used for @ least 10 years (afraid to power it on).

http://www.cordellaudio.com/instrumentation/power_level_meter.shtml

DeKay