This is a very interesting read, and I imagine that it is difficult for some readers to figure out "who is right" here. Without going into the findings for this particular loudspeaker, I think that one thing to look out for is whether or not the manufacturer seems to be 'infering generality from specifics'. For example, are they making some good loudspeakers and from that concluding that they are experts in modelling and measurements, or is it the other way around.
If you take KEF or Revel as an example, they have great white papers, you can follow what they are trying to achieve and why, and they show how well it works in the end via measurements. They happen to make loudspeakers, but their approach would allow them to switch into doing other products. Now, you may not like their sound as much as your own loudspeaker on a subjetive level, but you can still follow how they ended up with their product with a bottom-up approach. They are doing real research on a more general basis (although aimed towards loudspeakers) and then applying it to a particular type of product (loudspeakers) downstream.
To me, Danny is doing the opposite. He has designed some loudspeakers that seemingly perform well (and perhaps some duds also), and then infering from that, that he knows a lot about signal processing, transductance principles, measurements, and so on. However, many hobbyist can build speakers to a similar level and they can often have a good understanding of the underlying physics. Danny does not have white papers or any other publications to back up his claims, but he has his videos. So, you can instead dissect his videos, and you will quickly be able to poke holes in his reasoning. For example, he up- and downplays the importance of measurements, depending on whether someone critics his own loudspeakers, or if he is the one modifying a loudspeaker crossover from another loudspeaker company. Also, he will throw out ridiculus claims with total confidence, such as the Klippel NFS being just an averaging-machine (or something to that effect), which shows a complete lack of knowledge about spherical harmonics and multipoles. It would be much better to just state that he does not know these things, but he embraces his own intuition about it as facts. He is infering having general knowledge based on making some very specific products, completely overlooking his many unknown unknowns. There will be no way of convincing him of this, of course, so that should not be the aim for anyone.
As a consumer, what you need to consider is whether or not you will be happier with the specifics (the loudspeaker) if you know that the generalities (the overall knowledge/science behind making the product) are of a high quality also, or if you don't care. That is up to anyone to figure out for themselves. For me, the science behind the product counts, just as the looks count, but for others it is all about the sound and their subjective experience, and that is fine.
But if you more consider yourself a student of sorts, trying to learn the generalities (the signal processing, the acoustics, the structural mechanics, transductance principles, optimization), you really need to be careful with listening to YouTube video. Very often, the explanitions are too simplified or just plain wrong, and that is where it is becomes problematic. Sifting through that information is difficult without having some formal training, and many just regurgitate what they have heard their 'gurus' say. One bad sign to look for, is if they never refer to any journal papers or books, or if they always refer to the same loudspeaker cookbook as their 'bible'. You cannot learn all of the necessary general topics by studying these books aimed at the specific product. Something as seemingly simple as which way the loudspeaker cone moves is constantly being stated incorrectly, and you will see subwoofer companies saying in their videos that as the cone moves outwards is sees only the impedance of the room, and as it moves inwards, it sees only the impedance of the box, which is of course utter nonsense. But their products are good, so they are again infering generality from specifics, without understanding that their products work IN SPITE of their knowledge, not because of it. And that goes for other companies than loudspeaker companies, where many engineers have build their initution via analogy and not via first principles, leading to huge issues and missed deadlines.
It would be really great if more companies would show how they actually do their research and product development, going through the modelling stages with lumped modelling, simulation work, measurements, and the iterative process between these. It would give a more nuanced look at what actually goes into making a loudspeaker for some companies. Have for example a look at Purifi's latest blog post (
https://purifi-audio.com/blog/tech-notes-1/spk16-reference-design-12) and see how differently they approach engineering than GR "Research". Here, there is a clear research path leading to a product with measurements that speak for themselves, no downtalking about how others do this, and also journal papers so that academic peers have actually overseen some of the work. So if you are trying to learn, please seek out the proper channels.
