The flattest headphone I have, both in listening and graphs, is the V6. I've definitely heard flatter, and a lot of headphones measure flatter. The issue is that headphones that sound flatter, don't really measure flatter.
The V6 is bright. It is the brightest "neutral"ish studio cans I've heard. So, I would expect that the graph of the treble would be tilted up. But it isn't, the treble response on graphs remains between 0 and -3db (inaudible difference I think) of the target line from 2kHz to 5kHz, dips a bit and really starts rolling off past 10kHz. It remains either at or below the 0 level on the frequency response graphs throughout the entire treble, why does it sound treble happy?
I always assumed that my ears just were more treble sensitive than most. The graph says its flat, so I have to remember for myself personally, that flat on the graph means more than neutral level of treble and the V6's are called a bright headphone since most other headphones reduce treble even more so than the V6 so they can sound like its coming from speakers or something that gets treble attenuated by air. Yay. But apparently that isn't true.
Apparently zero on the graph is lying, and zero on the graph isn't really flat, and my ears aren't weird.
So why doesn't a headphone that follows the zero line well into the treble sound flat?