That is a good question. Planar headphones have been known to have really good/even low end response. However I think part of the issue is that they don’t excite the air the same way a traditional motor structure with high xmax does. So in theory they wouldn’t move air in the same way. That isn’t a big deal for headphones, but would probably be a problem in a room. I’lls ee if @elliottdesigns has anything else he’d like to offer up.