I would say most speakers reproduce much less than that range, and so does most people's hearing and most music recordings as well. Perhaps for a speaker to be a good audiophile or PA speaker it should strive to reach 20k, but very few systems or recordings will have a decent response down to 20HZ.
That can be good for movies and such, but just like the top octave, the bottom (20-40Hz) is pretty pretty unimportant for most music. In my experience a HPF around 40Hz often sounds better because the information down there just contains crap that takes up headroom, and demands a well treated room to not be a total mess anyway. My subs are designed go down to 35Hz, which I think is perfect for most music.
My point is really that a lot of people tend to assign a lot of importance to those extreme ranges even though they are a very small part of the listening experience. You can make an really amazing sounding system that only covers 50-16k, and there are many bad systems that cover 20-20k.
If you go chasing rabbit holes related to things like "singing at 18kHz", or "distortion at 15k" I think you are more likely to end up with the latter.
You need to understand that in the octave between 500 and 1000Hz, a 5 dB dip, or 1% difference in THD, will certainly have more than 10 times as much impact on the listening experience than the same magnitude in the octave between 5-10kHz. And between 10 and 20k we are talking 100s of times less effect, if any at all for the top part unless you are a dog or teenager.
Agreed.
A professional recording engineer will usually master a track with an HPF around 60Hz and an LPF around12kHz.
It's rather pointless to have a system that produces nothing more than rumble at sub frequencies, and cannot be heard above very high frequencies despite what the specs claim.
My partner, who builds magnificent open-baffle systems, is a 76year-old ex-drummer, (who used to play very very loudly indeed), and his hearing is more shredded than mine is not only because of his age, but also because of the common problem that musos often have from long-term high SPLs on stage. But yet both of us can both pick up deficiencies in high frequencies (that is, between 5khz and 10khz) when listening to high-quality recordings. We can both listen to a recording, and without taking response curves, identify peaks or dips, and their associated frequencies fairly accurately. Measurements simply confirm this.
There's very little important information above the 12kHz range (take a spectrogram of a good recording!) and it is pointless to chase after it. Again, as has been stated many times here, any male who is a few years older than his teens or twenties, simply cannot hear up to 20kHz. Yes, of course you might only-just be able to pick up a single tone at 15kHz. With headphones on. In a dead-quiet environment. But your ears are probably 20db down at that frequency anyway, and your actual range is nowhere close to that.
On the low end, maybe some movie theatre systems might have some vague benefit from a sub that extends to 20Hz. But it's pretty pointless if you're not driving at least 1kW RMS into it. You can't hear it anyway. Only feel it. And it will be rumble. Nothing more, I don't think anybody is able to identify what the notes are between 20Hz and 40Hz, so it will be for special effects, not for music.
Chest thump and gut-wrenching bass comes from the 50 - 100hz range, and 300W will do fine if that's what you're looking for.
I play electric bass. The lowest open-E is 41Hz. Even with the biggest PA systems, I don't think I've ever heard a decent, portable bass sub that goes much below 50Hz or so. It's just pointless rumble below that. Even a 5-string bass that goes down to 31Hz rarely plays the fundamental at 31Hz. A good example: look for Mad Men doing 'Ain't No Sunshine.' The bassist plays a beautiful open B in the intro. I have only ever heard one system reproducing that fundamental note, and it was a 4 x 15" speaker system. Most other systems will play the harmonics above that note, and it still sounds very OK to the ear. It's a psycho-acoustic thing.
I agree that many of the best systems rarely play 20hz - 20kHz, and that some of the worst systems actually do.