This is an oft-overlooked discussion, the comparison of headphone measurements made by different people with different setups. As catscratch said, it can make measurements made with different systems rather challenging to compare.
For example, Tyll Hertsens (Editor-In-Chief of Innerfidelity), as he describes here, uses a measurement head (the Head Acoustics HMS II.3). It is one of the industry standard tools for measurement. From that link above, you can read about Tyll's complete measurement system, including the acoustic isolation chamber he custom-built, the Audio Precision System 2 Cascade audio tester, and other components of his setup (and his methodology). Here are photos of his setup that he posted in that article (click the images below to see them in full size):
In one of the more recent headphone studies presented at AES by Sean Olive (Director Acoustic Research at Harman International and President-Elect at AES) and Todd Welti (Research Acoustician at Harman International), measurements were made using a G.R.A.S. 43AG Ear and Cheek simulator equipped with an ITU-T type 3.3 pinna. (More specific details can be found in the full paper--Convention Paper 8744--on the AES website.) Again, the G.R.A.S. piece and pinna is another industry standard measurement setup. Here are photos of the G.R.A.S., both without and with a ear/cheek affixed (click the images below to see them in full size):
Keith Howard in Stereophile also mentions that he uses a G.R.A.S. ear and cheek simulator; Brent Butterworth of Sound And Vision also uses a G.R.A.S. device.
I've been to several headphone manufacturer facilities, and have seen gear similar to the above-mentioned equipment in them (heads, head-and-torsos, and devices like the G.R.A.S. devices).
On the more homegrown fronts, purrin and Rin Choi have created their own setups.
purrin has elected not to use a dummy head or, to the best of my knowledge, a pinna. I'm not sure that his measurement system was ever discussed in great detail. When asked about his measurement system on Head-Fi, purrin called his coupler "semi-secret." (link) During a discussion at the Newport Beach audio show last year, when asked (on video) which coupler he uses (link), purrin (Marvin Chen on the video) responded: "I'm actually not using a dummy head. The reason is I actually did try a dummy head and there's some issues with that. With dummy heads you've got the ears, and the really good ones have got the tubes in them, and those create some specific resonances, that...don't necessarily represent what we hear. If I were to do a CSD measurement with one of those couplers, there would be resonances that are inherent to the human auditory system which I feel that the brain filters out. So what I actually did was I built a custom coupler. Essentially, what it does...it tries to minimize the effects of the ear, the ear canal, while at the same time try to be realistic of what we actually hear."
Here are photos of purrin's custom coupler setup (click the images below to see them in full size):
Rin Choi (who goes by udauda on Head-Fi) created his own dummy head that he named EURI (photos below). It is covered in a latex skin to "effectively simulate the damping effect of a human skin & insulate any acoustic leakage between the pinna simulators & the head itself." Inside of EURI can be found IEC 60318-4 occluded ear simulators. On his website, it seems to me that Rin is shooting for using industry standards (in terms of methods and gear), and, with his own measurements, compares his EURI head to commercial alternatives.
Here are photos of Rin's EURI head and the 60318-4 occluded ear simulator (click the images below to see them in full size):
Again, the measurement setups and methodologies can differ substantially from measurer to measurer. Some use more industry standard equipment and methodologies; still others claim to sidestep industry standards for individual reasons and/or claims of more accurate measurement results. So, as was stated earlier, it can be tough to make meaningful comparisons of measurements between the results of the different providers of them.
I absolutely agree with you, catscratch. I've spent more and more time with the Koss ESP-950 recently, and it is absolutely one of my top headphone recommendations even at its retail price of $999.99. Of course, if you find a better price than that, its value only increases.
FlySweep seems to also like the ESP-950, but, like you, catscratch, I'm certainly more enamored of the ESP-950 (than FlySweep)--however, I certainly agree with FlySweep's statement that the ESP-950's midrange is "liquid."