if what u mean by treble...my answer is NO. The HD800 has a warmer sound (noticeable in the MIDS and the LOWS). I would say is a typical of Sennheiser house sound with a much refinement. The HIGHS is more smooth and less zizzy IMO, but the T1 is not harsh at all, it just more neutral and more cleaner sounding and that what makes the T1 sounded more treble than HD800. But the T1 has more body to sound, more meaty presentation IMO. The BASS i think HD800 has a softer and deeper, but the T1 has more quantity of it and hit harder. Both are quite good. I can not say which one better. Is more like to personal preference. But if you like a neutral sounding, extreme detail and best sound image...i think should try the T1. The HD800 has a wider soundstage, but i do feel sometimes they just to wide at a time, luckily, the HD800 has a bit of that warmer side, so the sound somehow is just so "unbelievable" relaxing. Listening to HD800 is like you are in real live concert, inside the building...while the the T1 is like more private, when you are in the studio room, just you, the singer and the band and you can clearly hear and picture every single sound that come out -- is very intimate sounding IMO.
i love my T1 alot, but i like hd 800 alot too.