The Last Breakthrough in Speaker Technology

Larryi - there are some speakers that use drivers with underhung motor. Underhung is not very common because it uses very large magnet, but gives much lower distortions (better linearity). Example of such speaker is Adagio from Acoustic Zen. Sometimes tweeters are underhung to deliver better linearity at large displacements - like Morel Supreme.

I don't know why most of maufacturers use overhung drivers - perhaps cost.

I think speakers sounded a lot better with vintage AlNiCo magnets. Its nice to see AlNiCo magnets are starting to make a comeback!

While maybe not a major breakthrough Thiels 3.7 midrange is very innovative and well designed. It is my personal reference point for purity of midrange and vocal reproduction.

As an R&D/Process Engineer (Mechanical by degree) I see a lot of ideas and designs, and lots of them flop. Jim Thiel not only had great concepts but fallow through to make them really work in the real world. Now that is true genius.
3.7 midrange paper

Vandersteen Audio has more than a few
http://www.vandersteen.com/model7wp.pdf
Cheers Johnnyr

Martin Logan's curved electrostatic panel.