Already owning couple of over-ear headphones (Sennheiser and Audio Technica), I was slightly hesitant to purchase another pair of in-ear earphones after my last few experiences.
Having previously owned a pair of Sennheiser CX300 and CX500 (I understand the CX300 are quite a bit cheaper), I found them both to be unnecessarily boomy/muddy bass and lacking in treble.
The AT on the other hand has SUPERB level of treble, a little too high to begin with; however after around 4-5 hours of burn-in, the treble settled down to really show off the earphones at its best (apparently they get even better after 72 hours burn-in!).
I found the bass slightly lacking at the start (straight out the box) but again, after the initial burn-in, the bass was fantastic. Unlike the CX300/500, the bass was tight, controlled and showed a decent punch.
I would not hesitate to recommend these to anyone...
I tested the earphones with some of my favourite artists/genres ranging from:
Classical (Bach, Tchaikovsky, Mendelssohn, Chopin, and Schumann)
Dance/Electronic (Prodigy, Faithless and various MoS albums)
Hip Hop (BDP, EPMD, Marley Marl, Craig G, Big L, Lords of the Underground, MURS, De La Soul, Black Sheep, Black Moon, D.I.T.C, Sean Price etc)