I find it to have sufficient treble but not enough to make it "bright" to me the K701, DT880 are bright. It's a treble oriented can for sure but not like the treble is in your face. To me the added bass, more midrange and smoother treble make it sound darker. Of all my headphones the T1 sounds very similar to my HD600 which is considered dark. The main difference is that the HD600 has a treble roll off. I would still call the T1 slightly darker sounding. At least it sounds much darker than my other headphones that excludes the HD600 though.
From memory the HD650 is a much darker headphone than the T1. The HD650 being brighter than the T1 is impossible. The HD650 sounds much like a older K240M IMO and as such has a very rolled and subdued treble. I sold the HD650 because I really disliked it's syrupy sound signature. It make everything sound blurry and slurred. I also was not a fan of the muddy bass.
One day though I may try the HD650 again. For right now though I don't think I will.
Edited by Zombie_X - 7/23/11 at 1:54pm