This whole thing about people having different HRTF's, hence they hear differently is 98% bullshit. People mostly hear the same despite different ear, head, shoulder, body shapes. What's more likely is that people have different preferences, or some people, who would never want to admit it, have hearing damage.

Thank you.

This needs to be said more.

Yes, I agree Muppetface, that's something I've been rolling my eyes at for a while as well.  The idea that we all hear differently and thus prefer different headphones just isn't even logical.  We all live in the same world!  Maybe if someone grew up on Jupiter where sound travels differently or something.  But it's irrelevant how you hear because we all have grown up with the same reference.  If we all heard differently enough to account for the wild differences in headphones, people would be walking around saying "the human voice just doesn't sound good, it really lacks warmth" or "I can't stand female vocals, they aren't airy enough to sound good" etc.  For someone to even think the K701 was neutral because of their "HRTF" you know how crazy loud bass would have to be in the real world to make them want to compensate that much?  The real world is the reference.  No one tries to find colorations to compensate for the real world sounding off, the real world cannot sound off, unless they have hearing damage, and most likely because they grew up without that hearing damage so they have a reference to compare their current state to, and this reference from their better hearing is what they are looking to find with headphones. 

I'm sure there are subtle differences, but not enough to account for even 97% of how different headphones are. 

As Purrin said, and as I've tried to argue many times, it's people's differnet preferences, which comes from our personalities, and our goals because of the different ways we connect to music.  Because of how seriously flawed headphones are, we all scatter into wildly differnet preferences because of our different priorities and the different things we are willing to sacrifice first.  If you think the K701 is perfect, that means you're willing to sacrifice bass and warmth for that sense of clarity and air.  Same with the HD800. 

As headphones get closer to "perfect" or neutral/uncolored, you see everyone start to agree and like them more and more.  Which is why most people like the paradox and why most people like the JH13.  Because you get your cake and eat it too.  You don't have to sacrifice to get your priorities met. 

Actually, this is something I've been wondering about. How much does the shape of our ear lobe, ear canal, etc affect our hearing. I find it hard to believe that our brain filters out all the irregular features of our head, when it has no reference to calibrate to. ie, how other people hear. I also find it interesting that the equal-loudness contour has a similar curve to the diffuse field curve. This suggests to me that the features of the ears are not filtered out by the brain, and that our hearing is very much affected by these features.

The brain doesn't filter out the data assimilated from our head, shoulder,pinna etc.. It processes it to localize the incoming auditory signal to its approximate co-ordinates in the 3d space around the head. That is the purpose of HRTF according to my understanding.

The point purrin is making is that regardless of their measured HRTF differences, if you ask two persons standing together to located a sound stimulus they are going to point in the same direction.
Or may be I am assuming too much and two HFers may actually point in different directions to respect their different HRTFs.

HRTF is slightly bullshit when applied to headphones (IEMs are a different story.) It's an over-analysis of the issue. HRTF is never applied to typical speaker measurements. Typical speaker FR measurements (performed by Stereophile, speaker builders, etc.) don't use a dummy head, but just a free floating microphone.

Indeed, however the idea is that your head, torso, outer ear and pinnae are self-equalized by the brain to sound flat or rather, correct. Headphones remove the head and torso from equation - both of which matter mostly in low frequencies. IEMs also remove the outer ear and part of the ear canal - much more pain in the rear end to match.

Also, good mastering houses (and good audiophile setups) attempt to take away many of the wall/room interactions with room treatments. So why headphones would want to simulate "diffuse field" to such a large extent puzzles me. The SRH1440 comes to mind.

Same here - that's why I equalize them not to diffuse field, but independent-of-direction. (any-field) This is in fact easier - just have all the sine tones sound equally loud. The curve is pretty similar supposedly, but the differences fall in the highly sensitive area.
When I want a room (diffuse reflections) on top of that, I add a convolution reverb. A very minor reverb mind you (-30 dB early reflections) helps remove the "artificial" feeling.

This whole thing about people having different HRTF's, hence they hear differently is 98% bullshit. People mostly hear the same despite different ear, head, shoulder, body shapes. What's more likely is that people have different preferences, or some people, who would never want to admit it, have hearing damage.

True. HRTF are far less relevant for headphones, except ITD/ILD which simulate head and torso, not affecting higher end frequency response that much.
IEMs are different matter though.

Also, the differences are within 6 dB, also limited to 3-12kHz range. Far less than anything detected by the usual hearing tests, which are only sensitive and specific enough to pinpoint 10 dB hearing loss. Of course 6 dB in those frequencies is quite noticeable coloration, but in positioning the result is mostly that the soundstage gets flattened and somewhat narrowed.

For example, HEAD's ID compensation (which Tyll uses) is a too insensitive in 3-6k range for my ears (flat to me represents a few dB cut there on Tyll's graphs), otherwise matching pretty well.
This took a bunch of headphones and IEM equalizations as well as speaker equalization by ear in an anechoic chamber (cross referenced with another measurement graph), but at least now I know.
It is an expensive and time consuming mistake to correct. I'd love it if you posted a difference curve between your compensation and HEAD's for cross reference purposes.

Perhaps that one was derived from older people with mild hearing loss or something? Just the result of averaging, some people will definitely have their hearing compromised.

As far as what Viking said - Yeah - I agree. Headphones bring a level of intimacy, cleanness, and detail extraction not achievable by speakers.

Four thumbs up out of four. Theoretically it's achievable, but it's real hard.

I don't think it's impossible, the important part is simply that all frequencies reach the eardrum with roughly the same amplitude. The feel of bass is something people willingly give up when using headphones. The thing is that no one really knows what a dead neutral headphone is cause there's no set standart for comparing frequency response and it will always be slightly different for everyone.