On most consumer sources and amps, they sound very bright and a bit shrill. But on a higher-end amp, the bass tends to become fuller. The midrange is very good on these headphones. In other words, the CD2000 is one highly sensitive (efficient) headphone which requires the use of the right amp in order to sound its best.
You won't believe how good the CD2000 is until you plug it into a right setup. The drivers of the CD2000 are so sensitive that I can hear differences of sounds on the left and right channels, even at a low volume level.
Using the Metric Halo ULN-2 and the CD2000 (driven by a decent SS amp) reminded us of the ATH-L3000's details and bass quality with better transparency.