I got these headphone a few days ago and feel compelled to add a comment or two to offset the nonsense that is being bandied about by people that apparently know little about music reproduction and Hi-Fidelity.
The headphones are the last item in a long chain. For a truly neutral set of phones (ie very little coloration of their own) they will produce faithfully what they have been fed. With the enormous variety in recording, engineering, mastering, coupled with the enormous variety in sound reproduction equipment it makes zero sense in talking about one item in that chain being responsible for the overall sound, particularly, the last item in that chain, the phones.
Garbage in garbage out is THE maxim in hi-fi reproduction. I found the 350's to be superb headphones, and, a fabulous bargain at their price. The talk of "modding" is just silly, as if "one size fits all" cures for "too bright" and other complaints could be addressed this way. If you like to tinker, have at it, I rebuild my own tube amps for many years, but stuffing tissues or felt discs into these phones is not a "mod". They were not thrown together by amateurs, these are seriously excellent phones, for any price.
I tested them in my 2 Xiang-Sheng DA-03A dac/amps. One with the TE7022L input usb board one with the better XMOS-U8 board, the standard dacs from my Pioneer Elite bluray player, my Oppo 83SE (super dacs), my SMSL M8, and analog through several tube preamps, even my old Sansui 9090 (warm and luscious). They are excellent in all applications . Optical source to the Xiang-Shengs (they have a 5670 tube in the circuit) yielded the best resolution and separation, with great balance.
The pure analog tube preamps were the warmest, also with excellent detail and separation. Due to the wonderful Mullard and RCA tubes that tubey "magic" comes through loud and clear with these phone. Yes, they are very clear and pure in the high frequency range so you want to have all your gear up to snuff as these phones will quickly point out any weaknesses in your upstream equipment.
Feeding them crap will sound shrill and irritating, they are faithfully reproducing what they are being fed. Your headphone choice will not "fix" your bad sound. These are truly excellent headphones, and a bargain to boot. Do not insert truly Hi-Fi headphones into a lo-mid-fi rig and expect great sound.