Here is my quick measurement of the Stealth, done with my own ears, by just playing pink noise target is Optimum Hifi, and I get a heavy 9khz peak. This is averaged over 11 different positions for the Stealth, also averaged for left and right.
View attachment 156525
for comparison the Focal Elex (green) and Utopia (blue) also exactly my ears etc:
View attachment 156528
I am not sure how nobody so far didn't notice that 9khz peak, it sounds just horrible to me, also dunno why it doesn't show up in Amir's measurements, but that peak is noticeable in the other measurement to some degree.
To me the headphone sounded just horrible, not sure why many claim it to be the "world's best closed headphone". a complete letdown soundwise.