I agree with this. The most important thing, I think, is actually to get other research groups to replicate the experiments, and see if they come to the same results. I do research for a living, albeit in a field which has nothing to do with audio at all. And in the fields in which I work or which I follow closely, you can't take findings for granted unless they are replicated and corroborated by other research groups. There is a reason people speak about a "replication crisis" in science... scientists often get small things wrong, even though they act in good faith, and it's difficult to know whether one has actually measured what one thinks one has measured. One of the most important things is actually to have different research groups working on similar questions, as this makes it more likely that mistakes or limitations are discovered.
What troubles me slightly with lifting up the Harman research to the status of an undisputed audio gospel is that this is basically one research group, who had clear commercial interests in what they were/are doing. I don't mean to disparage their work at all - Toole, Olive and Welti and the others have done an immense service to the audio community by putting so much of their work out in the public domain. Really. The problem is not that they have been doing this this work - quite on the contrary - it's rather that so few others have bothered to replicate or challenge the studies! "Psychoacoustic loudspeaker science" is basically such a small and underfunded field... and unfortunately it's probably going to stay that way, given that high-end audio seems to be destined for the same end as the dinosaurs.
But take the issue of the dipole speaker, for example. In Harman studies, no good. In one of Søren Bech's studies, however, the dipole received the highest rating given a particular placement, and the worst rating, given a different placement.
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Source:
https://www.researchgate.net/public..._sound_quality_-_a_review_of_existing_studies
This is just an example. Now it would be relatively stupid to claim that flat frequency response on-axis and smooth response off-axis is bad. Nobody thinks that. The interesting devil lies in all the details in speaker design. How much weight should on-axis flatness be given, relative to behavior off-axis? There is a genuine trade-off here - equalizing the speaker to improve off-axis may make it slightly worse on-axis. Waveguides or horns
may improve directivity patterns, but how about those HOMs? And what about things like transient response, dynamics etc? (here's a paper I read some time ago on that:
https://eprints.soton.ac.uk/426110/ )
I don't mean to spread FUD here. The Harman way of doing speakers is obviously a very good and valid way of doing speakers. In my sighted listening I usually tend to like speakers that are designed according to the Harman philosophy. But until other research groups start replicating Harman's experiments, I'll probably not become convinced that flat response on-axis and smooth response off-axis are the
only things that matter.