Hi. I am a long-time headphone user, but a newcomer to the world of decent ones. I recently bought a pair of HD600s after reading so many good things about them. My previous pair were HD215s, which were reasonable, if slightly light in the bass. My amp is a 1999 Sony CMT-SD1 - an integrated CD player, tuner and amp, not ideal but it's all I currently have available. It sounded OK with the 215s and I figured it would sound at least as 'OK' with the 600s (i.e. good enough until I upgraded). On first listen, however, I was shocked at just how much more bass there was with the 600s. Too much, in fact. Whereas the 215s had a slight lack of bass, it was still in proportion. The 600s just sound bloated and woolly, with what seems like a boost in the 100hz area. Not only this, but the mid-frequencies seemed distant and there appeared to be a slight roll-off in the treble, although I initially put this down to being used to the 215s. The general sound is not very impressive.
So I did some reading about things like output impedance (all new things to me!) and although I am still uncertain about what it all really means, I get the impression that what I am experiencing may be due to an impedance mismatch between my amp (I cannot find reference to the output impedance of the headphone jack on the Sony, but I assume it is probably on the high side) and the headphones. I tried the HD600s directly out of my iPod Shuffle and was surprised at how much more balanced everything sounded. The bass boom was gone, and it generally sounded better to me. Looking around for other things to plug into, I dug out my old Soundcraft Spirit Folio mixer. This also displayed the boominess, although to a lesser extent than the Sony. Again, I have no output impedance rating for the mixer.
So, I can only conclude that I either need a new amp, or different headphones. If the former, I don't want to spend more than £150 (perhaps second-hand). I get the impression that another integrated amp (even if vastly better than the Sony) may result in a similar sounding output with these headphones, but I may be wrong (there surely must be people successfully using HD600s with an integrated amp). So I'm now looking at headphone amps and I gather that as low an output impedance as possible is considered a good thing with the HD600s.
I'd love to hear opinions about whether what I'm experiencing is due to impedance or something else entirely. I can't bring myself to believe that the HD600s are really supposed to sound like this.