So back to the topic.
How Kii are fighting against unwanted resonances in mids and highs?
Braces helps only at lower range.
Some companies like Focal or bw made a special thing for the tweeter's, q acoustics made a triple layer of MDF plus dual layers of ''gelcore'' in between, this help to make the cabinet very innert not only at lower range. KEF made his ''meta material'' for the UNIQ, thats for the same thing...
What about actives companies?
Neumann, Kii, d&d are kind of sleeping for what i see, Neumann is the most sleepy one, they just don't keep launching new products. And the KH420 went never passive, so the cute FR was only because of DPS. Or improve the tweeter. The kh420 has a tweeter that has lower directivity than the mids, they can launch the KH430 with wider directivity tweeter that match the mid-range. The tweeter has low directivity, is like 40° vs 55° of the midrange.
D&d did a better job in directivity than Neumann, in fact is really good.
What about Kii? They are very expensive.
How did they fix the midrange and highs resonances? at this price point i expect excellent spacial effects in the soundstage, not just tons of EQ for the FR looks nice.
Metal is worst fighting agaisnt mids-highs vs MDF. Metal cabinets ressonate at higher frequencies vs the MDF, MDF/hdf was never a bad material.