Your favorite Electrostatic, Panel spkr

Not to pick nits, but the famous tweeter in the big Maggies---3.7, 20.7, 30.7---is not a magnetic-planar, but a true (not quasi-) ribbon. So is the tweeter in the Eminent Technology LFT-8b.

bdp24- you are absolutely correct. The rest of the speaker is planar magnetic. You can not make true ribbons very wide. Magnetic energy drops off at the square of the distance so you can not spread the magnetism much of a distance. The Diva Mid range which was a true ribbon was a little over an inch wide and that was pushing it.The woofer was planar magnetic. It is also the reason the Maggie tweeter is a bit fragile. The ribbon runs in a "U" shaped extrusion with slots cut in it. Magnets are glued to the sides of the "U" The ribbon is tacked down every other magnet alternating sides with a little glob of blue something or other. The ribbon is aluminum foil laminated to a very thin layer of plastic. Most of you have played with aluminum foil. It bends easily and if you go too far it will crease. If you keep bending it back and forth it will work harden and break. It will break if it gets overheated which you may have seen if you barbeque 

barbecue with it. It is very fragile compared to other materials but nothing else works as well as aluminum. I tried making a titanium ribbon speaker with titanium foil and neodymium magnets. It worked great until the ribbon started to get warm (higher resistance than aluminum) then it expanded and started flapping and waving all over the place. So much for that experiment. Anyway, the Magnepan tweeter is much more durable that the Diva tweeter was but Magnepan tweeters are blown all the time. Fortunately, Magnepan supports their speakers well.  

@richopp
The ML HQD was an interesting look and I assumed that you wasn't suggesting for OPs room, but as a point of interest. I should have put a LOL after my comment.

I Always enjoy your posts.......Jim

A true ribbon CAN be made in a wide width (Apogee did it), but it's expensive. Such a ribbon is very insensitive, and apparently it's impedance has to be very low (Apogee's sure was). A difficult loudspeaker to pull off, but some consider the Apogees the best they've ever heard. I've never heard one, the best I've heard are imo ESL's, though magnetic-planars have their charms.