Difference in terms of sound: 1) If you like the HD800 but somewhat struggling with the ringing treble, this will be perfect for you. Its still a bright sounding headphone, with very similar sound signature to the HD800, but with the peaks trimmed-off. The treble on the HD800S is smooth and very captivating. 2) Vocals sounded more natural, less chocked up. The HD800 sometimes gives me a feeling of the vocalist being strangled (exaggeration). Think it's something to do with the balance of high mids and high treble. They did a good job on the HD800...