Somebody posted a link on AC a few months ago for a quicky frequency hearing test.
Some vendors extol the value of harmonics well beyond 20,000 Hz, but I've not read of anything definitive and not sure what recordings are available that go beyond that anyway. Seems to me that you'd have to have your source and amps capable of the same before you could take advantage of such speakers. And even if you had all that, would it be a good thing or bad (revealing somehow hidden warts)?
In my mind the bigger issue is: Do audiophiles really want the truth, the whole truth, and nothing but the truth? I think not. We want entertainment, in various forms to suit our individual tastes (unlimited dynamics/sound pressure levels, extreme detail, hyper realistic, room filling sound staging, powerfully deep bass, musically satisfying, lush/warm/exaggerated/whatever tainted sound).
