Yes, it would be nice to find a planar driver that could do 90hz. It does not exist....you have to make your own....like Magnepan and Diptyque. Even most planar and electrostat hybrids cross over between 172 and 500 Hz (Sanders sound, Janszen, Eminent tech, PS Audio, etc.). And they have fanstastic midrange. Regular woofs are fine to about 500 hz....above that you want much smaller drivers or better yet planars. The trouble with Magnepans are that they have no serious dynamics (mostly because the frames are so flimsy).
The speaker I am making is for me.....However, I will share every bit of information so that those with the skills and desire can make their own. Not a money making thing. Later in the year I might? get the tweeters that are used in the Caladan and make a clone.......however, I just don’t see how a forward facing cheap tweeter crossed over at 1K and non time aligned and be anywhere near a dipole planar that is time aligned crossed over at 400hz.....and you can stack the tweeters and make a 32 inch line source for even lower distortion and better vertical dispersion. These planar drivers are just $50 each. We shall see....er hear.....soon.