In reply to:
As an example, my Adcom power amp (rated 325Wpc into 4 ohms) has nifty instantaneous distortion indicators; I have NEVER managed to turn them on even when listening to highy dynamic music/soundtrack materials at insane (basically intolerable) volume levels in my 5000 cu. ft. room.
I put some calculations into a spreadsheet and came up with the following:
Note: this assumes a speaker sensitivity of 88dB/W/m.
8 ohm, 3 meters, 29 dB loudness = .001V, .001amp, and .00001W. This would be a really quiet passage. 85 dB, close to my average loudness level, would be 6V, .75amp, and 4.5W. Say I crank it really really loud and the peaks bring the music to 100dB. This would mean 34V, 4.25amp, and 145W of power! So as you increase power levels, the instantaneous peaks of required power grow exponentially.
Then don't forget that full-range speakers demand a lot of low-impedance current to power the bass. The "8ohm compatible" Paradigm Reference Studio 100 v.2 has an impedance hovering around 4 ohms for most of the frequencies below 80 Hz. When dealing with very low bass, it becomes feasible to hit 105, maybe 110dB in total power for a moment. Now you're well into the hundreds of watts. Don't forget how many subwoofers have their own power source of 100, 300, even 1000 watts of power.
Boiling frogs
In reply to:
...There are many ways to do this, including the classical frequency sweeps, pink noises, square waves, and more fashionable impulse and step responses, but these are in fact 100% equivalent to each other when measuring amps
100% equivalent?! Absolutely not. Manufacturers choose very different ultrasonic frequencies at which to begin rolloff; some begin the rolloff below 20kHz, even with solid state amps. The resulting square waves can be virtually square with super-high bandwidth amps @ 10kHz, whereas the lower the rolloff, the more rounded the square wave.
At this point we have established that all amps measure differently, though typically the resulting frequency response should be within a decibel. 1.5dB or so is considered close to the threshold of just noticeable difference (JND), right? Well you inspired me to delve into a psychology book. This threshold is usually determined by providing one stimulus, hiding it, then incrementing or decreasing the intensity and showing it again. It can also done by slowly but continuously altering the intensity; this is how you boil a frog without it noticing.
Moving pictures
But what happens if you are staring at a light bulb and it instantly increases in brightness by 1%? Even if its below your "JND" threshold, you can easily notice an abrubt change. Consider color depths on your computer screen. 24-bit is typical, which is 16 million colors. Some people go even higher to 32-bit if they do lots of image work; that is over 4 billion colors. Yet my psychology book says that humans can discriminate about 7 million different colors. Why the difference? Our senses are tuned to use contrast whenever possible; in the real world, colors are not broken into 16 million discrete colors. They are continuous. On the computer screen, an artificial contrast or step is created between each quantum, and our visual system accentuates this difference, so we see a line if we look closely.
Have you ever seen LEDs that seem to flash when you walk by them? When we stare at a fixed spot of pulsing light, it begins to look solid I think in the hundreds of hertz. However, when that light source moves, our threshold jumps to the kilohertz. So in our quantified world of man-made pulses and lines, we need to increase the numbers several-fold in order to properly fool us into sensing continuity, be it vision, hearing, or other senses. I believe this is why DVD-audio and SACD are noticeably better than CD: they up the numbers almost to the point where it sounds no different than the continuity of an LP, but without the low resolution.
Impossibly conclusive
SOOOO, for those of you still here, I will hypothesize that with constantly changing music, our sensitivity to frequency response is higher than with fixed tones. If we can hear a symphonic peak clearly, at 11 million times the power level of a whisper, and if we can distinguish both within a second of each other, then perhaps we can hear all those subtleties that many engineers would love to dismiss. For those of you who have heard the differences (I'm pretty low on the audiophile scale), then this will resonate well with you.
-Cooper
