For me, basically any high end headphone outside of the HD650, R70X, and Focal Clear MG sounds too bright to me without EQ or mods. But the budget stuff like from Koss and most earbuds sound too warm and dark actually. I have the most issues with IEMs. Compared to open backs like the 650, every single IEM i've tried is WAY too forward from 3-6 kHz, causing an unnatural upper mids and lower treble glare to everything. I need a measureable dip there in order for it to sound natural like the HD650. The Sennheiser IE800S and the Final Audio E5000 sound better, but still bright around 5-6 kHz. I'm convinced this is because of my personal ear resonances and preference for lower volume in the upper mids, not because every IEM is flawed. In fact, Axel Grell talked about this in one of his more recent presentations regarding his Grell brand IEMs, the fact we all have naturally different ear resonances that can very by as much as 20 dB in some areas.