[Ethan Winer]

I'm not sure that amplifier crossover distortion is a sine wave phenomenon; rather, I think it's a discontinuity in the transfer function. But maybe it can be deconvoluted into sine waves.

Yes, everything can be broken down to its component sine waves. Thanks to Fourier for discovering that many years ago.

one order of magnitude (a ten-fold) increase in amplifier power output will give a 10 dB increase in loudspeaker sound pressure level (ignoring power compression for the sake of simplicity) - rather than a 20 dB increase.  I don't yet understand the reason for the discrepancy.

Power is volts times amps, and when you double one the other doubles automatically. So this gives twice as much dB increase as you'd get from doubling only one. That is, 1 volt into 1 Ohm draws 1 amp = 1 watt. 2 volts into 1 Ohm draws 2 amps, hence 4 watts. This is a 6 dB increase rather than 3 dB which is a doubling of power. Likewise 10 times more volts also draws 10 times more amps, so the increase is 20 dB rather than only 10 dB.

--Ethan

[Duke]

Thanks again, Ethan.

Just to make sure I'm following you here - the THD spec is referenced to voltage, not wattage - is that right?  I understand that a doubling of voltage equals a fourfold increase in wattage.

Duke

[Ethan Winer]

Just to make sure I'm following you here - the THD spec is referenced to voltage, not wattage - is that right?

Yes, exactly. Most dB stuff in audio is referenced to voltage rather than power. Even in a power amp it's the voltage that is usually measured when assessing noise and distortion. So 10 percent distortion is 20 dB down, 1 percent is 40 dB down, and so forth.

--Ethan