first thanks you for the great answer, we obviously have different perspectives, and different ideals, but it sure was interesting to read.
still you assume a few things that aren't facts as far as I know. you got the logic right (at least it seems right to me ^_^), but you start with wrong(at least to me^_^) assumptions.
even in the audible range, our brain will try to recreate the missing parts of a sound based on experience. that's how we believe some moderately clipped bass to be louder than they are, because expecting the top of the wave becomes the same as hearing it. if it works(to an extent) for the loudest part of the sound, I'm pretty convinced that harmonics past a certain order, or decays below a certain level, are both assumed as existing even when they're not there. because of how easy it is to assume a pattern and imagine what will follow.
but of course below a certain level we don't care simply because it's to low to care or simply hear it, feel it, perceive it... we have our own sensitivity limits and frequency range limits like would any microphone. those are physical limitation plain and simple so I don't see the point of going beyond those limits. but it seems like you do.
in fact from what I read, you seem to take the sound of an instrument as a complete piece and believe that we can't hear it as being real, if something is missing. like some kind of cake that wouldn't look as a whole if the cherry on top is missing. as said with my example of slightly clipped bass, I don't believe that we actually need all the data to hear all the data. some are necessary, some aren't. just like we recognize a person even if half his face is in the shadow or making a face. we have that capacity/curse of altering the truth into what we feel we need. visualizing things from blurred or incomplete images, just as we can recognize a song on a crappy phone speaker. and that capacity goes a long way with sound. even a messed up guitar will be a guitar, because what else could it be, so we'll assume it is. from that point our brain will try to hear the guitar in that mess and change what I'm hearing. at every level this happens and I don't think we need the 80Th harmonic of a note for it to sound real as a string. the first few sure, it's what makes the sound. a few more why not, they do give a feel if they're not too quiet and don't decay too fast. but at some point it will end up being just a tiny noise and wouldn't participate in any meaningful way. and what instrument does actively reach 20khz and above? I've used that great page for years now http://www.independentrecording.net/irn/resources/freqchart/main_display.htm and I always supposed that what was shown was accurate. as the notes on the piano reference stop at 16khz I concluded that everything reaching 16khz might go beyond it, but that's it, wouldn't it mean that most other instruments do not even reach 16khz even with the harmonics?
if this is not wrong, then all that passion for past 20khz is pretty much for cymbals(my least favorite instrument of all when drummers mistake strength with talent) and people breathing making some involuntary high pitched notes in the process? because most pieces of violin that I heard don't wander too much on the higher notes. simply because it rapidly sounds aggressive and not so much musical, I would guess.
I just don't think we need to have 100% of the created sound to hear it right. or exactly, even with 100% of the sound we wouldn't hear it right because we would add stuff on our own. we would add the same stuff every time we hear a given sound, because again we do it from experience so we would make the same conclusion and "understand" the same sound every time.
people can find a sound natural with a 3% thd tube amp, what percentage of the sound of an instrument is past 20khz? that's a dumb way to look at it, but I keep the idea that we make up for the differences up to some point, so we really don't need to have everything right for it to feel right.
and of course, as I don't believe we actually receive much information above 20khz anyway(even non conscious information), missing a part we never heard isn't missing a part.
just like our cone and rod cells in the eye aren't enough to get the real spectrum of the light reflecting on objects, we don't need that unseen part(UV or whatever) to come out of a photo or a tv to make it feel more real. it doesn't feel real but that's mostly because it's 2D and our eyes don't get why they don't have to refocus to look further away in the image, and because the rest of our field of vision tells us the light is wrong. but it has nothing to do with the missing UV. the only real sound is the sound we can hear. it doesn't matter what the instruments are actually making if it's out of our reach. and to me that reach is around 16khz, so let's say I could make something out of up to 18khz right now. not hearing, but receiving some matter of soft cues. having or not having the rest won't change a thing. that is what I believe and what you don't. the rest is a way to justify that simple point of view I think for the both of us. I keep thinking that the differences you percieve don't come from the 20khz and more. there have to be something else being responsible for the difference you get.
back to the subject, I've tried the k1000 for a minute or so, and while it's not a bad idea for binaural (given we wouldn't move the "wings" once set right). it gets us free from the pads and a bunch of sound reflections so obviously that could help. I don't know how well it does in high freqs, but what I did notice and was expected, because... well ... science. was how light it was on low freqs. the roll off was no joke.
so for me that would be a no go unless we can get something with more bass. but wouldn't more bass be a reason why the trebles get rolled off? ^_^
anyway if it's a good match for flat sound in the high freqs, then at least imaging and placement must be great. I did enjoy it but didn't pay that much attention to imaging except that is was indeed different from your usual headphone.
