I am just thinking out loud here, but it would seem to me that everyone's hearing is different, but not so different that an entire industry would risk mass producing products on the basis of individual hearing capabilities? Can you imagine the commercial disaster that would entail from manufacturing product on that basis?
The Harman Curve as I understand it is a way of reducing that risk and to assist in the design and manufacture of product that for majority of people is the preferred sound regardless of age, sex and consumer type (audiophile and novice listener).
If the Harman Curve can be determined as successful from not only a commercial standpoint but also the best sonic solution in regards to sound fidelity that is a win-win for all concerned from the naive consumer to the golden eared audiophile.
I think it was
@solderdude that said EQ makes all headphones sound similar but not the same and that has been my experience although there are some headphones that cannot be rescued by EQ and the Sony 7506's for instance IMVHO is one of them.
Parametric equalization has been a revelation and a god send for me, thanks to ASR.
If everyone's hearing is markedly different then that is a nail in the coffin of the concept of the "audiophile" right there, because there cannot be a standard of agreed upon fidelity if preference and opinion are the only guide. You need the numbers because otherewise your opinion is just the same as any other schmuck out there. Considering BOSE and their customers have been judged as schmucks by audiophiles for decades, it is not without irony that they may have been enjoying high fidelity products such as these headphones while the rest of us have been listening to noise.
I bought my wife QC25's years ago as she travels quite a bit and I thought they sounded very nice I may have to borrow them and try some EQ and see how they sound.