I received my TH-X00 on Monday and been listening to them since then. The bass seemed flabby from the start, but now has tightened up. Overall sound signature suits me very well. They are slightly U-shaped, enough not to be shouty with some music. There's a noticeable bump in mid-bass, but I like it, it give body to string istruments (I listen mostly to classical music). That's what I disliked about TH-900 when I had them: they were to ethereal, not enough body in the mids. It might be ok for pop music, but not optimal for classical. I think they are better headphones than Beyerdynamic 1770 (the only headphones I compared them side-by-side) in all areas except isolation. From the memory I like them better that LCD-XC, EL-8C (these were horrible), TH-900 and -600. Beyer 1770's are my second favourites, the biggest drawback is comfort: too much clamping force.