dcguy73
Formerly known as dc_guy
The HD 660 S is definitely more HD 600ish to my ears. Definitely a personal preference thing on the HD 650 vs HD 660 S. The HD 660 S falls more in line with more warmish neutral headphones such as the HD 600 and the DT 1990. The slight hardness is akin to that found in the HD 600 but it's less bothersome than what is found on the HD 600, it's more like the DT 1990(balanced pads) where it's there but not a cause of fatigue. I have found the slight hardness is only on certain systems though, I personally found the HD 660 S to sound less hard and more musically flowing when using optical over USB.
The Amiron Home fills in more laid-back sounding headphone like the HD 650 for me and is why I don't have any desire for the HD 650 currently. It's more trebly than the HD 650 but it has a similar relaxed character to it's sound.
That is an excellent elaboration on what I was trying to say. You nailed it.