Yeah this is basically the gist of it. There are, in my view, two 'correct' ways of developing a target curve for the 5128 that achieves a result people actually like - and that's important because theoretically you could just use DF for everything and then represent it against a slope, but I tend to think that's more confusing.
1. One is to calculate the Harman in-room response for the 5128 (and there are ways of doing this), and then apply the shelf filters from the research. So in other words, get to the same starting point for the new system, and then use the results of the Harman research to specify the shelves. This approach would result in a target that
looks somewhat similar to the existing Harman target, with the bass shelf, but is then applicable to the new standard. This is also the approach I would expect Dr. Olive to take if they were to fully develop a public target. At the moment though I think they're just using a stop-gap internally based on the delta of results, and unfortunately that doesn't quite work for a reference curve since headphones behave differently depending on the head they're on - not to throw shade at them or anything, it's understandable as I don't think the 5128 is the focus of current research. I suppose if they were able to validate the same on-head behavior among the different systems somehow it would justify continuing with that, but that's not a study I'd expect from them anytime soon.
2. The second way is to rely on diffuse field head-related transfer functions (or DFHRTF). In overly simplistic terms, think of this as like... a flat speaker 'calibration' that each measurement rig has (and every head/ear), and conveniently it's also very close to the Harman in-room baseline. So while DF for the GRAS doesn't
look like DF for the 5128, compensating to them for their respective rigs yields a comparable result. But because people generally don't like the way DF sounds (it's too bright for most listeners), we can apply what the Harman research
validates - that people prefer a downwards tilting slope for both speakers and headphones - to the DFHRTF of the 5128. There are a number of benefits to this method, like that you can more easily get a 'high res' version of the target, and on the practical end, you can apply the same concept for comparable results to any measurement fixture or even in-ear mics on real people. Note - they won't necessarily look the *same*, because headphones behave differently depending on the head/rig. But they will be using the same target principle, and thus comparable.
So, in my view both of these approaches are valid, we just think there are more benefits with the latter, and that it fits more closely with the wider body of acoustic research than just Harman. Also... and this is a point I'm not sure how much I care about... but going with the DF plus slope approach also means we're not limited to Harman conditions - meaning the specific speakers/room used for that research. Going with the former approach would mean trying to... 'inject' previously baked-in anchors that aren't really needed. I think the counter argument here is that we've been assuming those conditions for years so we might as well go with what's familiar. But this also means future outcomes are slightly 'poisoned' by those conditions as well - I say in scare quotes there because as Dr. Olive has pointed out recently, you could do a lot worse than the Revels that were used.
One last thing, I just want to address the comment on the 5128 not being meaningfully better than the older GRAS systems and some of the thoughts around chasing the new measurement standard turning into gatekeeping. While it's true that the older rigs are still useful, as Jude has pointed out a number of times the B&K 5128 is a better representation of an actual human than ever before. In practice, it's not more 'accurate' for where the majority of audio information falls (between 200hz and 10khz) but below and above that, it is better. How much that really matters is still up for debate since at high frequencies positional variance is a massive factor anyway - not just on rigs but on real people too. But review platforms getting these new rigs isn't just about benefits in the minutia, but rather moving to the the new measurement standard the 5128 has pioneered.
Then, ideally, with our proposed target approach we can make even the inexpensive clone rigs comparable up to a certain point. At the moment that's not doable because the shore hardness of those pinnae is too stiff, meaning you can't actually use the GRAS DF for it. But I'm told there is a closer pinna to the KB5000 in the works for those as well, which could in theory make our proposed target concept applicable. In my testing when I used an official KB5000 ear on the clone coupler, there's still a resonance at around 12khz that shows up every time, but apart from that it was quite close to the official GRAS. The bottom line is that our intention with the DF plus slope approach is to provide a target that makes more measurement rigs cross compatible and have the opposite effect of gatekeeping older or less expensive ones - even if there is still some work to be done there.
Anyway, we'll be doing more videos on this topic soon - maybe like an FAQ to address some concerns/questions. But I figure I can also do a bit of that here,
just keep in mind that our target is still a work in progress:
Q: Does this mean the Harman Target is bad or otherwise unimportant?
A: No, we need to distinguish between the specific target many of us are used to with measurements done on GRAS KEMAR based systems, and the large body of research behind it. We want to make use of the research
outcomes, like the bass to treble delta that people preferred, but can't port their specific target that reflects that over to the new system for the reasons mentioned above. Also, the Harman Target is still great for GRAS systems, and we will still be able to use it as a reference point on those systems.
Q: Will we be re-measuring all of the headphones that had previously been measured on the older systems?
A: Yes and no. We will of course be re-measuring many headphones on the new system and providing those graphs, but we don't have access to everything in the back catalogue. We can, however, apply the new target to that data for cross compatibility. For new headphones that come in we'll
also be measuring them on the GRAS as well to see how they vary across different heads.
Q: Why not just show raw graphs for everything?
A: While we'll continue to provide raw graphs, those done on GRAS systems will look different from the ones done on the 5128 (or any other system), and so there has to be a rig-specific reference target associated with the data. Additionally, as a matter of what defaults should be, compensated data is technically better because it avoids the common illusion of reading parallel lines against one another. There will be a video on this, but in short, yes, we intend to provide both.
Q: Why not just use a well-known headphone like the Sennheiser HD 650 as a reference point?
A: While this is useful as a point of comparison - and I imagine would be useful to many who have heard that headphone - this approach won't work for anyone who hasn't heard that headphone. Additionally, this is less helpful for
evaluative purposes, because even the HD 650 has a particular 'flavor' to it - as do all headphones.
Q: Can't you just EQ a headphone to Harman on the GRAS and then use the 5128 result as the reference point?
A: No, largely because headphones behave differently on different heads, as mentioned earlier. But also even if a 1:1 match were somehow validated, this would still default a heavily smoothed outcome and we'd lose the 'high res' option.
Q: Will you have a measurement database to compare results?
A: At some point, but until then published results will be compiled in a
forum thread like this one.
And of course, there will be more to come as we fill in more of the picture with this new target concept.
