I went back now and had a look at the other designs. The really awful one looked more like there was a problem with the device. It's got crazy high levels of all distortion orders. This usually happens when something is vibrating or hasn't been sealed properly. Like the interface between the tweeter unit and the waveguide.But they are not all compression drivers… There are several domes on my list.
As I already pointed out, there are plenty of 1” CDs to be found that do not exhibit this much distortion. The only problem is, that JBL doesn’t seem to make them. It’s not a limitation of technology, but the brand.
Obviously, the designers had to deal with a list of compromises here. And from what I gather, this is the case with numerous models, many of which seem to have the same issue where a lower-quality CD or tweeter is crossed too low to a woofer. And again, if it was just this one speaker... fine, but it's clearly not.
Most of the speakers only show a very slight increase in distortion around the crossover frequency, it's usually only 2nd order, and when driven quite hard. I do agree that things could be better, but on the whole, it's not a major issue.