I feel I should add a couple of points here. My comments about avoiding EQ are directed towards the best, most highly engineered phones that appeal to the listener out of the box - even if they're not perfect. In those cases, I think the 'magic' on offer is an extremely complex balance of factors which, in my experience, is quickly overwhelmed by even the most sophisticated EQ (and much EQ is not very sophisticated ...). The 'distortion' I'm talking about is not just the noise from power supplies, cables and additional processing, it's the skewing of the balance that's been painstakingly engineered in the phones. I think phones, unlike loudspeakers, are really all about the tiny factors that cohere to produce a singular effect. That said, I accept we all 'EQ' our phones to some extent: we choose particular amps, cables, etc. For instance, I always liked the Sennheiser HDV820 amp with my HD800S phones - partly, I think, because it has a 40 ohm output impedance which tilts the spectral balance in favour of lower frequencies - I think it can 'improve' the sound of the HD800S. I also prefer analogue crossfeed. That was one of the reasons I chose my current amp - Moon 430HA. I always use crossfeed because I think all phones sound better with it - even my Stax SR-009S phones (I add an iFi Pro iESL energiser to the Moon to drive them). This is obviously a very subjective account, but I've never managed successfully to change the basic character of any of the phones I've owned. I'm interested in classical music, so I prefer phones which reference a diffuse-field frequency response curve - like the HD800S. If I was interested in electronic music, I might be interested in phones which reference the Harman curve - more like the Empyrean. They're very different beasts. I feel I get the best results by finding phones that are close to what I'm looking for, rather than trying to re-engineer phones that really aren't.