There was alot to chew on in the most recent Noise Floor livestream. Much of it was more on the esoteric side. And some I agreed with and some I didn’t quite.
I think Harman should have used diffuse field compensation for their measurements and target response curve. Because this would’ve made the results more broadly applicable. There were several problems with this though.
The biggest is that the rig that they used for most of their studies did not have a head or torso that could be measured in a diffuse field. I assume that they chose the GRAS system over some other options (with heads and torsos) because it was more affordable, and potentially more accessible to a broader swath of users and developers in the audio field. A DF curve would’ve been an invaluable tool though for translating their work to other measurement systems.
I think they also believed there was enough similarity between the different types of rigs that a raw target or response curve developed on one system would generally be applicable to others. This is understandable because most of the B&K, GRAS, and Head Acoustics rigs that were in use at the time were based on 711 couplers, and were also compliant with other standards for measurement. The shapes of the heads and pinnae were all somewhat different though. And they all had somewhat different resonant characteristics. So the raw target translated better to the systems closest to the one Harman used in their research. Namely, the GRAS. And less well to the other systems.
The other reason is that they had already ruled an unmodified DF curve (without a slope) out as a target preference curve. And probably did not want previous unsatisfactory targets like DF or FF to influence their final results.
The lack of DF compensation impaired the broader adoption of their target though.