No, that is not what you say. What you want people to think is that the measurements more accurately predict listener preference. There is not a single soul that cares about the impedance matching of the measurement rig against a study.
I have no idea of whether there is a statement I, or Headphones.com, or whomever you're indicting here can make to dispel this idea, but I'm going to try anyway: No, what I want people to think is that
the 5128 is more accurate in its approximation of human ear impedance. This is because
the 5128 is more accurate in its approximation of human ear impedance. I have
repeatedly, at substantial length, on this forum and others said that I don't think acoustic Z is particularly important for circumaural headphones. This makes sense from both a math standpoint and from my own measurements comparing occluded canals and DRP measurements. I have said this over and over, and will continue to say this over and over, and ironically I have continuous (friendly) arguments with
@oratory1990 about it (with him in favour of more accurate Z as a necessity).
For
in-ear designs, there's a quite reasonable case to be made that the 5128 provides more accurate results to human perception. Ironically, the main area where this would be the case is the low frequencies, where the 5128 matches the human ear's impedance more closely, as opposed to the trumpeted-about improvements in the 8-20khz band. In practice, how significant this is will depend on acoustic Zout of the earphones in question, which is natural since we're talking about the pressure level in the canal.
Are these fairly small points? Yes, absolutely. Is the 60318-4 standard still as useful as ever it was (which was quite useful indeed) for measuring headphones? Yes, absolutely. Is anyone coming to confiscate all the 43AGs and 45CAs? If they are, it won't be anyone affiliated with me. It's surreal to me that
conducting measurements on a standards-compliant measurement system has become offensive to you here.
As the study authors state, the response is with one standard deviation until about 12 to 13 kHz
In full, this is the pertinent section of the paper
While it would be pedantic to make much of the difference marginally exceeding 1stdev in the 1-5khz band, it bears noting that the "shape" of the impedance curve is significant here, with the 60318-4 undershooting on Z in the ear gain band, and overshooting at low frequency. Just as with output impedance and load impedance in electrical signals, this has a different implication for the resulting eardrum FR than a flat difference in Z across the board.
Again, this is likely a pretty small effect, and in the places it's been potentially documented (e.g. Crinacle's comparisons of 60318-4 and Type 4620 IEM measurements), the impact on frequency response has been moderate, a few dB less bass in some cases. It's nothing that would make any reasonable or sane person discount 60318-4 measurements - but it is an example of why accurate loading can be significant.
What you have to also keep in mind that the above are under strict laboratory protocol. There is no way a reviewer is going to be able to assure compliance with their protocol. Indeed, even the authors of the study failed to do that for their full set of volunteers: "A total of 44 subjects entered into this study, but 12 were rejected because reliable measurements could not be obtained." That is nearly 30% exclusion!!!
Which, if the aim of reviewers was to measure wideband ear impedance, would be a real problem. However, while the input Z of the human ear
does change with insertion depth for insert earphones (thus all this "propagation" business), that does not mean that it varies randomly, it's just about the modal resonances at high frequency shifting a bit. More accurate ear Z means a more accurate load, which, for cases where that matters, does mean somewhat more predictive measurements. It's the same as the argument for a 60318-4 coupler over a .4cc coupler, in fact, which
long precedes demonstrable sound quality preference prediction differences between the two couplers.
So no way you want to run with the punchline like you are using. As I have repeatedly stated, the claim of accuracy here is a marketing one looking for verification.
Listen, if it would convince you that you are incorrect about the motivations involved here, I will go to the head of content tomorrow, on Independence Day, and say "Cory, I need to make a really boring video about headphone measurement systems. It's gonna get like 100 views, but it's gonna have the truth, and it's gonna mend a massive cleft of understanding and assumption of good faith, and that's worth it", and then I will write a script that specifically highlights why the 60318-4 is a pretty damn good system for measuring headphones, how the 5128 differs, and why those differences are ultimately rather small, record it, and post it. This isn't even a bet or something, you need do nothing, if that will legitimately reconcile this misunderstanding, I would be happy to do it.