Damping Factor - Interesting article

Every amplifier has some feedback. Even emitter resistor is a form of local feedback. The problem with global feedback is, that it corrects with a delay (phase shift from input to output). This delay produces overshoot in time domain (odd harmonics in frequency domain). 40dB feedback means, that amplifier has 100x higher gain without feedback. Since amplifier delays signal from input to output, signal fed back and summed at the input is late. It make very little difference for slow sinewaves, but for fast changing input signals amplifier, for a moment, has 100x higher gain and overshoots. Benchmark is trying to time correct it with separate error amplifier (two sets of output transistors).  This overshoot shows in some Stereophile reviews as square wave response.

+1

Doing 4 things at once including posting here :-) ... sorry for my error. I meant impedance is halfed, but had V-squared/R on the brain :-)

An amplifier that doubles in power as the impedance is squared will keep the most consistent anechoic output.

Buddy, you went the wrong way. I know of no amp that doubles power as impedance goes from 4 to 16 Ohms. That is certainly not an ideal voltage source anymore.

No conflation. It was postulated that ESL sound bright due to higher power output to the speaker as the impedance drops. I claimed that was not true, because though the power goes up, the anechoic response w.r.t. constant voltage over frequency is flat to down at high frequencies.  The postulate w.r.t. bright due to amplifier interaction is not the reason, the reason is different dispersion and how that interacts with the room and creates a room response that will be bright (if not done right).

You are also conflating dispersion with relative differences in amp output
vs. impedance.

atmasphere,
I deleted my old post questioning your article as I misinterpreted what your point was and where you were coming from. Put my head into a different mindset and completely agree in principle w.r.t. what you were communicating w.r.t. constant power for a tube output configuration. I don't have a blind attachment to 0 output impedance / infinite damping factor, and I expect most who do don't even know the details of why and why it may not be best from a system standpoint.

Most modern speakers are simply wrong because they have uneven impedance curves and their impedance is too low in the bass region which then means you need amplifiers with low output impedance/high damping factors/negative feedback/high current supply to try to correct these electrical flaws.Two wrongs trying to make a right.When what we should be using is speakers with benign impedance curves in combination with current drive /high output impedance amplifiers because current drive amplifiers sound so much better than voltage drive.http://education.lenardaudio.com/en/12_amps_8.htmland  https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&u...

It is not an electrical flaw in the speakers. It is primarily a mechanical design choice. The site you linked is good, but it is easy to draw the wrong conclusions if you don’t read in depth.

A pure current feedback output is not ideal as it will provide a peaky frequency response, and provides no additional electrical damping for the drivers which can be beneficial.

The damping factor the speakers see is never near 0 either due to the crossover impedances.

Neither was is really "wrong", just different and the right answer is probably somewhere in the middle ... though I would say most accurately, the correct answer is speaker specific amplification with an amp per speaker, but that is a tough nut for most companies to crack and not easy to market. Good on SGR tackling it at some level.