It's amazing how people here things so differently.
I had the HD650's twice, the first pair were stolen, and used after market cables (equinox & Silver Dragon v2) and although I never had them at the same time as the T1's I am absolutely certain that in my system the two sound nothing alike. The T1's are in a different league in every attribute. IME the T1's have far greater clarity,detail and speed. The Hf's are far better in extension and presence. The bass is a lot deeper,tighter,faster,impactful and rhythmic. The midrange is a number of levels above in clarity,openness,transparency,neutrality and naturalness.
The differences are so pronounced,to me, that I find it hard to believe anyone could consider then as sounding similar.
I also don't think the HD650's are anything like the LCD's either,thankfully!