Interesting. I learned a lot about closed backs after reading this article and then checking listener’s squiglink. See, I own a Takstar Pro 82 and the same attributes appear there: a scoop around 200-400Hz, preceded by a boost; a valley around 5kHz; and a treble peak somewhere around 10-11kHz.
I hope to see an 82 graphed on 5128 someday, it would be specially interesting due to its mechanical bass switches.