Your measurement appears to be considerably off. A headphone that measures flat through the mid range and treble will sound extremely raised in the treble. A substantial HF attenuation most be present in any proper headphone, to compensate for the air absorption that would occur with real speakers vs. the listening position, and the off axis ear pickup of treble frequencies, in which the head and ear system partially deflect, causing further attenuation.
Originally Posted by gene
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