The harman target was made with the old gras or something rigs and the best rig right now is the 5128. Think of the 5128 as the klippel of headphones. As good as it gets for headphone measurements. And there's no harman target for that, just a diffuse field one, and since it's not done by harman, will you consider this an actual reference point?
Opinions differ on the 5128 as they also do on target curves. Dr. Olive agrees on that point too.
It certainly is not 'the Klippel NFS' for headphones.
BK5128 mostly differs in the way the simulated ear canal is shaped and the microphone is positioned which is closer to that of a human ear canal than the previous standards. Perfectly usable for research on acoustics but the older standards were also pretty good at that.
The pinna that was used for the Harman target was not even a standard pinna but something they cooked up themselves.
This does not invalidate the very extensive Harman research nor the reason why they started the research nor why they made the choices they did to determine a (their) standard.
References (test fixtures + target curves) are for research so one can get comparable results when doing research.
Product testing is another thing than research but one can use the same tools.
side note:
I am still amazed that people really believe their pinnae, ear canals, ear condition, seating for the measurement, seal, (silent) revisions, product variance, pad condition and preference actually matches that of any test fixture with a certain copy of a headphone and genuinely believe that importing some EQ will turn it into a true reference for them.
The science is clear about that too (that it isn't but that it complies to a standard).
Sure, in most cases (the 'majority' of people) it will make headphones sound 'better' to them so that's the win.
A (slightly smaller) 'minority' prefers a different 'sound'. Those are usually the 'I hate Harman sound' people for whatever reason they might have.
Regardless how well a curve fits to some standard it is bound to differ from
personal perception.
The proof is the fact that people's opinions on the sound of
each headphone model differs from 'the best there is' to 'it sounds like total crap'.
Below 100Hz and above 6kHz all test fixtures and curves have an increasing degree of error.
Older people may remember the heated debates about which headphone was 'best'... the HD650, DT880 or K701. Consensus was never reached.
Everyone that loves Oratory's work and actually looks at the pdf's (and not blindly downloads a curve) knows that his measurements have limitations, are not done on the industry standard Harman uses (but is close to it and also is not the BK5128) may have noticed the text on the pdf to tune certain bands to taste and even suggests which bands they are.
When a headphone sounds good and shows no major problems on (different) test fixtures it can be successfully used for mixing
when one knows how it 'translates' to a reference. That's where the trick lies and the important part here is the used 'reference' (speakers in a room usually).
The same goes for music enjoyment b.t.w.
After all the recording is all we have and in order for that to sound good the reference during the recording must be good (circle of confusion).