Very similar to the 250s, but this one seems to have a little bit less energy in the tremble (8k to 20k). Might partially explain what I've heard at T.H.E. Show (DT990-600 + Schiit Valhalla.) Could it be that the 600 ohms are less bright than the 250 ohms or would it be manufacturing variations. BTW, very good driver matching.