Sennheiser HD800s is an improved flagship, over ear, open back headphone in a black finish, includes both a 3m cable w/ 1/4" and 3m cable with 4.4mm terminations and has a slightly tweaked sound vs the HD800, to provide a warmer (fuller) sub bass response and smoother treble response. In this way Sennheiser improved the sound of the original HD800.
The 300 ohm headphones work well with a variety of amps we carry, including the RME, SPL and new iFi Neo & Signature. With the smoother sound and less tendency towards a bight sound, the HD800s gives more consistently pleasing results with a wider variety of amps. The HD800s build on the HD800's ability to provide one of, if not the best, open, wide soundstage, giving music a natural, spacious feeling, as well as a very balanced frequency response and enormous amounts of detail.
HD800s have very spacious earcups yet excellent ergonomics, fitting close to the head, little clamping force and a light weight compared to other top of the line models. Tip - Wearing glasses does not effect the sound much at all - there isn't much of a seal, so the earpads can sit on your glasses' arms without changing the sound much.
From Sennheiser: