Ok, that's very cool that Resolve & Oratory are working on 5128 targets of their own. Yeah, I understand why that's a quick & dirty method re what I suggested in my post and that Harman got flak for it re using GRAS Harman equalised headphones to transfer from GRAS to 5128 - I also don't think it's a particularly good idea for the reasons you mention but also because if you're going to take that approach then you may as well just stick with using the GRAS. I agree that it makes more sense to create a fresh target for the 5128. Praps @Resolve can think about getting his B&K into a good listening room with some Anechoic Flat speakers and create a target by measuring at the eardrum of the 5128 to sine sweeps from the anechoically flat speakers (in the same way that Harman did it for their GRAS in their studies). Then you could tweak bass & treble levels to taste for a few or many participants, then Bob's your Uncle you've got a Target Curve for the 5128, lol! It would be quite difficult and time consuming to sort out all the participants depending on how many you were aiming for, and it would require quite some effort & time to get the whole study setup. I'd say that kind of approach would be the best thing to do with the 5128 to create a target curve.That's exactly what Harman themselves did to "transfer" the Harman target to the new 5128 (see here).
It's also what they took considerable flak for from the audio science community as this method is quick and dirty, with less than optimal results.
You just can't really compensate for differences in acoustic impedance, as the response delta between GRAS and the 5128 will be different for each headphone.
Sure you can find a compensation curve that'll on average get you closer to compliance, but the individual error for each headphone will be quite considerable regardless.
The right thing for Harman to do would've been to remake the target from scratch.
As a result of Harman's shoddy work and their decision to keep their results under NDA, people like Resolve and oratory were encouraged to do better, and are now working on 5128 targets of their own.
Yeah, I get your points @solderdude re listening levels & effect on bass & treble, and also your point about the quick hack I suggested in my previous post would mean you're just calibrating to an old standard (GRAS) like you mention, so it should instead be a Target Curve that is created "fresh", like I replied just now to StaticV3 in this post. I don't know how ambitious and how much time & effort Resolve has got to create his Target Curve for the 5128, it is interesting though.5128 ear + ear canal is closer to that of an (average) human being.
The acoustic impedance also differs so the results will differ.
This is why the 5128 would be a good choice. T
he more measurements are made public the more people can relate to the plots.
Note that the exact same headphone on different fixtures always will measure different and the exact same headphone will also be perceived differently by different individuals.
The goal of the 5128 is to get closer to the average human in measured response.
The thing is IF you are going to construct a target based on the 43AG you are basically calibrating to an older standard that isn't as anatomically correct and thus give incorrect measurements even though it was considered one of the 'correct' fixtures (but not the most 'correct'.
Resolve is on the correct path it seems but may not end up with a Harman target. While the Harman target may be preferred by many (the bass boost part) many find it a bit too much. The Harman target is impressive sounding and may well be correct for those listening at say 70dB average (all day listening level) but some like to enjoy music at a louder level for say 2 hours tops. For these folks the bass target proposed by Resolve may fit that better. Also the bass levels of 5128 are measured slightly lower so a Harman target on the 5128 will appear to have less 'bass boost' in the raw graphs anyway.
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