Nice video review Amir, it's good to watch these to get a bit more explanation of your measurements, etc, that would be harder & longer to describe in words in your written reviews, so it's a good addition to see these clear videos from you. Particularly I could see your angle on the large drivers combined with large earcups being there to stimulate the soundstage effect, and those same large drivers potentially causing challenges in driver control that might have caused that chewed up frequency response & Group Delay which you indicated likely caused your impression of lack of fidelity on a long listening session. I think there is something in that regarding a "chewed up frequency response" (fine grass jagged) and fidelity, because the smoothest headphones I have are the ones with the least "fine grass" - the HD600 and the NAD HP50. My K702 I think is also there in terms of fidelity, but there's not many bonafide measurements out for that one, so I can't equate my experience to the measurements on that one just yet. My Hifiman HE4XX has some good soundstage and some fantastic clean bass once EQ'd, but I do feel there is a slight lack of fidelity there, there's not massive amounts of nuance/detail in the music, and that headphone also has quite a lot of "fine grass" in the frequency response - so I think there could well be a link between "fine grass" in the frequency response and it's negative effect on overall perceived fidelity.
Do you think the air gap when you were measuring the headphone (not perfect seal), do you think that could have worsened the "fine grass" within the frequency response and Group Delay and somewhat problematical distortion?
