The bass is more accurate on the KRK 6400 than on the Grados. People complain about the DT1350's bass, too, but it's more accurate than the boomy stuff most headphones produce. If you look at the Headroom graphs, the 6400's frequency response is similar to the DT880 600, but with less of a treble peak, more extended extreme highs, and a slight dip in the 60-70hz range, if I remember. And of course, it's closed. The impulse response is not as exaggerated and the bass square wave is better. It's a very good sounding headphone when amped properly... remembering this is a 32ohm headphone that needs an output impedance of 3 ohms or less. It's sounding nice from the E7 right now being fed the Emu 0204 and I'm not missing the ESP 950 as much compared to when using the T1350 or modded HD25. The KRK is very pleasant like the Koss, though not as pristine, delicate, or grit-free. It's also less dry than the DT1350 and seems a little better balanced overall. I only think the ESP 950 and the ER4S exceed the KRK 6400 when looking at their overall performance. ESP is the most delicate of the three and the most refined, but lacks bass tightness for some reason. ER4S is very neutral with exceptionally tight bass, but not the most delicate or refined in comparison to the ESP. The KRK isn't really super delicate, super neutral, super refined, super distortion free (like the ER4S, ESP, or DT1350), or perfectly tight in the bass, but it's extended, surprisingly neutral, not too dry or liquid, has above average bass accuracy (even compared to the DT990 and DT880... ignore volume, I mean quality), and isn't too bright or hard usually. ESP is warmer, smoother, more open, and more delicate without question. Sent it back due to hums, though. For the price the KRK goes, it's highly under rated, in my opinion. Its closed sonics is probably its biggest handicap.
