Keep in mind that X2s benefit from some burning in - 100+ hours and they open up quite a bit. Initial impression was a bit muffled, not anymore. Got mine from Amazon US a year ago - no glue, WOOX made in China.
As a side note, I also have a pair of A5-Pro, awesome closed cans for office use, same story with the burn-in (studio pads really change the sound stage on those, still on the muscular bass side but a bit more flat response than the stock pads). A5-Pro is a bit easier to drive than X2, I would say that not all headphone outputs are powerful enough for X2 especially portable devices like phones.
larsvI've never heard any changes due to "burn in" in any of my headphones. Though some of the Koss headphones with titanium coating need to flew to loosen up. The PRO4AAT sounded restricted because of the thick titanium coating. so that's a form of burn in I guess, but any changes are very negligible.
As a side note, I also have a pair of A5-Pro, awesome closed cans for office use, same story with the burn-in (studio pads really change the sound stage on those, still on the muscular bass side but a bit more flat response than the stock pads). A5-Pro is a bit easier to drive than X2, I would say that not all headphone outputs are powerful enough for X2 especially portable devices like phones.