Kept trying out your ES5 measurements for a little more than a month - I like what you did with the rockbox.
However, when using your EQ settings with better source such as my desktop setup (Audio-GD DI-V3>Anedio D1), I still think you are forgetting to attenuate frequencies past 4000Hz. There is a huge dip between 4k Hz and 4.7k Hz and a couple of peaks surrounding it.
Unfortunately, there is quite a bit of variation between ES5s in the higher frequencies. In fact, in my ES5 alone, my repeated measurements consistently show that I get drastically different results for my left and right channel (left channel dips around 4215 Hz while right channel dips around 4415 Hz).
However, these phenomena can be seen in the Golden Ears graphs for the ES5 too - both the left and right channel discrepancies as well as the dip at around 4.4k Hz and the peaks around it.
This high range (maybe around 3.5k Hz to 10k Hz) is critical for both a transparent soundstage and a natural tone (I'm too lazy to get citations, so you'll just have to trust me here).
Thus, by ignoring the 4k Hz+ range that has full of problems, the highs on the headphone sound "warped" and veiled. This is not a problem with the Rockbox could never do crystal clear highs anyway.
What equipment are you using with your ES5 btw? (Esp. your desktop setup)
Edited by Zalken - 3/20/13 at 3:22am