Pbb said:
"In the treble range what is mind-boggling is that many believe that the response should go way over 20 kHz when most adults can barely hear beyond twelve/fourteen kHz."
You're the first person I've EVER heard mention this online, even though I've silently wondered about it for years. I remember from the old days when "high bias" cassette tapes listed a frequency response extending up to about 16,000 hertz, and an audiogram I had a few years ago showed a slight rolloff at 12,000 hertz. They normally only tested to 8,000 hertz, but had the capability to test up to 12,000, which I requested and they did. Twelve thousand hertz is REALLY a high frequency, yet we audiophiles classically consider 20-20,000 to be "full range," and then sometimes go even further by purchasing super tweeters (out to 50,000 maybe?) and subwoofers (some going down to under 10 hertz).
I can say unequivocally that the Rel Storm 3 makes a big positive difference in my system. I cannot comment on supertweeters, other than to speculate that they may be useful in repelling insects and rodents, both of which have higher frequency hearing capabilities than do humans, even audiophile humans.
So.....I agree with the generally accepted 20-20,000 as defining "full range," but like Pbb I wonder if it's overkill on the high end.