It's Tyll's prerogative not to trust his own ears. Just as it's my prerogative to take his writing with a large grain of salt, having bought the K550 he put on his Wall of Fame.
Edited by Shaffer - 3/21/14 at 11:30am
I see. Really just a matter of preference; also depends on the genre of music you are listening to. I have tried some songs where the K550 is overly bright, but I think they perform relatively well across the board for all song types generally. I think they are very comfortable and perfect for listening to music while I work at my desk at night for hours on end. I listen to music on low volumes while working and the sound signature of the K550 is perfect for this. They're really detailed and accurate.
I've never tried the A900x but with my small head, I think I'll hate the wing design. And I think it's a bad design where the earcups cannot be adjusted to let the earcup lie flat to your ears. The K550 fits me perfectly as they clamp with minimal force.
Might I also add that you have to place the earcups (they are HUGE) correctly. Align your ear so that it's on or near the edge of the earcup; or align it yourself so that the cone points clearly towards your ear canal. You have no idea how many people don't know how to use headphones properly. If you don't do this, the K550 also sounds overly bright.
That video is pure failure though: It's a dumb test and a waste of time. To have any worth, they'd have to make sure that the two headphones are identical from the get-go, which was never done. So all we know is that the two headphones FELT or sounded different. Might have just been the pads too, the pressure on his head, etc. It definitely does not prove beyond the shadow of a doubt that break-in makes an audible difference.
As for validity of break-in: Can't remember the site but a speaker manufacturer measured drivers before and after break-in and there was measurable and significant difference. Ah, there it is: http://www.gr-research.com/myths.htm Headphones work in the same way and have similar components, so they're bound to also be affected. But to what extent? That remains to be seen. I'm skeptical that the effect is dramatic, especially since it lacks the crossover of the speakers, but it might still be audible. Might... ;)
 Also the guy started off saying he wanted to do a double blind test. Guy doesn't know what a double blind test is... Anyhow, as I said, waste of time. If you don't start with two identical headphones, the only thing you can conclude is that those two headphones weren't identical, not that break-in has an audible effect.
Break-in isn't caused by heat, it's the suspension loosening up due to the forces applied to it. The principle of a dynamic speaker and headphone driver is exactly the same & they both have the same components. Headphone driver on the left, speaker driver on the right:
And besides, like every other material they have to obey the laws of physics, and when you apply force to a flexible material such as driver suspension, its flexibility will change over time. It's not a matter of if it will change, it's a matter of how much. For speakers, it's significant, for headphones, can't say I've seen definitive evidence yet. http://www.innerfidelity.com/content/evidence-headphone-break-page-2 http://www.innerfidelity.com/content/measurement-and-audibility-headphone-break-page-2
No hate, but it sounds like you been listening to a whole other phone than I did when I listened to them lol.