For mainly mids comparison I used the Angus and Julia Stone "Black Crow" and "For You" tracks (320kbps) (male and female vocals) at first than London Grammar.
Angus and Julia Stone "Black Crow" and "For You" tracks (320kbps)
K340: Less 3D. Less stage width/height/depth... Mids are slightly more forward. Definition is excellent. Details are clearly heard. Slightly drier sounding compared to X2. But very very enjoyable on the mids.
Switching to X2: Real 3D image. Stage is huuuuge! Layering is better. Mids seems slightly less forward compared to K340 at first. Than suddenly I realize that the stage is so large that everything is located in an appropriate distance to each other and the mids are not less forward anymore (my brain adjusts the new sound stage and signature in 5-7 seconds). I can clearly say - even the K340 is excellent on mids- with X2 a veil on the mids are removed (I can't say K340 is veiled even a tiny bit but in comparison this is the situation).
London Grammar "Hey Now" from youtube KEXP radio record.
K340 did an excellent job here. It sounds fantastic with the London Grammar. Extension of the female highs are so well pronounced that my ears can convince myself that she is singing live in the small screen of the iP Touch right in front of me
) May be recording also helps to differentiate the results. Dunno. Or may be thats the female vocal I want to hear... Also this record is made in a small studio and doesn't require a large space. So K340 stage fits better. I prefer the K340 slightly more over the X2 for this recording.
Extra:
Comfort: X2 is better.
Fun factor: X2 is better.
PS: K340 is a legendary (cult) electrostatic-dynamic headphone produced about 20-25 years ago by AKG. My K340 is highly modded and re-cabled with SPC wire. Also I have to add that K340 has at least3 different versions (some believe 4-5 versions). Mine is the most balanced version which is going to die with me (will never sell it).
I used the same setup to play the songs as mentioned on my previous post (2 post earlier).
My listening levels are in between 60-80 dB. I generally use a scientific grade and calibrated SPL meter to adjust the sound level of my HP and iems.