Thank you again Matthew for this post in which you have covered a lot of ground on this topic. I thought I had read just about every credible (in my opinion only obviously) article Dr. Google could find but I might have missed Cordell's 2007 show one.
There is nothing (could have missed something though as I was speed read..
) I would disagree based on my own understanding, and experience on the topping of "clipping".
That's why when people come to AH and ask at least once a week the questions related to "Do I need an external amp?, Does my amp have enough juice for my 4 Ohm speaker etc., kind of question.., I would typically ask them to first try and figure out how much power they actually may need for their applications/systems and report back, and go from there. If I think a simple question might suffice, I would high ball it based on their speaker's specs that include manufacturer's recommended amp power, maximum power handling number etc. and state my assumptions.
Some would come back with a number, even with a screenshot of the calculator they used, making it easy for my follow up response, after checking to see if they had input the data correctly, such as speaker sensitivity (important as most calculator are based on a fixed impedance of 8 Ohm), number of speakers and room gain allowance. I don't mean those things are exact, but if one or more are way out of whack then the final results could be almost meaningless. Once a number is reached, then I would typically bump the calculated number up by at least 3 dB, example: if I think they need 100 W, I would suggest a 200 W amp and that is exactly because I am concerned about clipping during peaks, not knowing what their favorite source contents are.
In my case, amps typically output between 0.1 and 0.5 W on average so I know any of my half a dozen power amps will never, or almost never clip.
All in all, clipping or not is not that hard to know as they (or was it I..
) said, its the distance, speaker sensitivity, impedance, phase angles, and SPL stupid!!
I posted multiple times my experience in comparing my AVR-X3400H (that I tried for about a week) with my separates including the 4B SST and Halo A21, that I couldn't hear any difference whatsoever no matter how hard to try. During that time, I also use REW to check and see if the tiny AVR altered the FR and it didn't. So I am certain it's not THD, FR, DF, TIM of modern well made amps including AVRs, but much more about voltage and current capability such that as long as the DUTs are not pushed close to their limits all would be good. Any time I see someone reporting night and day difference, especially when heard even at "low volume", I would say there's something wrong in their comparison listening setup, or they just say things that's likely wouldn't apply to everyone else.
In your linked Cordell article:
"At the end of the session the attendees were polled in a very informal and unscientific way as to which amplifier they thought was the tube design. They could answer one amplifier or the other, or they could answer that they honestly could not tell which was which.
There were no "night and day" results. Indeed, for many attendees the differences were difficult to hear. Moreover, those who perceived a difference were just as often wrong in selecting which amplifier they thought was the tube amplifier. This shocked all of us."
So yes amps likely would clip more often than people think, but is the "all about SPL stupid" (my simplified version of the truth
) that would determine whether one's amp would clip and how often.
In this case it was a comparison between a 35 W DIY tube amp and a 250 W Denon power amp. It just showed how silly people get thinking just by replacing their amp with a different brand, or simply adding an external 125 W SS amp to their 120 W rated AVR for two channel listening, they would get better sound quality like opening up their speakers, hearing details they would never hear before.
