So George, are you saying 400Hz is too high for crossing over to the ESL panel.Yes, to me small narrow esl panels can’t go low enough, so the bass has to be bought up to it, and to me they don’t marry well at these very sensitive midrange areas, it’s a compromise but still very listenable.
The proper fix to me would be to have a much faster lighter cone 6-7" midbass unit to match the speed of the esl’s at 400-500hz and then have a 10-12" 10-12" bass unit below that at 150-100hz but that’s going to be complex and expensive.
The other fix is to have a bigger wider esl panel that can go down to 150hz like the Monolith and Neolith and then have a good 10-12" dedicated bass unit.
Cheers George