How much power?

[Mac Guy]

<font color='#000000'>If it takes a doubling of wattage to achieve a perceived increase in sound level of 3 db (the minimum the human ear can discern?) will there be much difference in a receiver with 100w rating and a receiver with 170w rating? &nbsp;I realize each will clip higher but unless the upper limit is more than say, 6 db, what's the benefit of an increase of only 70w? &nbsp;I have read that for a perceived &quot;twice as loud&quot; increase, an amp must increase a given wattage by a factor of 10...does anyone know if this is accurate?

Mac Guy</font>

 

[PaulF]

<font color='#000000'>Mac Guy,

The latter is correct. If I remember correctly doubling the power, or adding a second source with the same output level as the first will increase the perceived sound level by 23%.

I don't know about 3dB being the smallest change the ear can hear though, there's a lot of equipment with 1dB or even 0.5dB channel trims.</font>

 

[gene]

<font color='#000000'>Depending upon the frequencies and amplitude and sensitivity of the human ear in question, it is entirely possible to hear changes as little as .5dB in level. &nbsp;In fact, I read in some audio journal that .2dB level changes are detectable.

As for power, yes doubling the power does add 3dB in loudness or more importantly in headroom during music peaks when you need it the most. &nbsp;You have to realize that all power amps are not rated equally.

Case in point, I am currently analyzing an amplifier from REDesigns that is only 75wpc in 8ohms, but 150wpc in 4ohms and is fully regulated. &nbsp;Thus when the line voltage sags, the power delivery remains much more constant than a more powerful unregulated amplifier. &nbsp;

For more info on watts, dB and perceived loudness, read our FAQ:
Watts, dB, Loudness FAQ

Usually the more powerful receiver offers a higher current power supply that better copes with low impedance low efficient speaker loads. &nbsp;So there is definate merit to having a more powerful amp provided that all other things are equal, particularly SNR.</font>