Hate to go negative here, but I dunno , I just don't see any of these big radials ( sectorals ) offering solid performance down to 400hz ( without a bit of EQ ) .

Here's ( a blowup of the FR for ) the 329a , which has the same 220 hz flare rate as the 311-90 .

3

Maybe that @ 10db an octave rolloff below 600hz works for the OP and his 400 hz Xover point / otoh, maybe not .

Personally, I'd rather see FR that's flat down to 400hz so that I can choose how to mess round with the rolloff, via caps & coils .


<> cheers