The AR9 was real acoustic suspension but a hanger on. By that time bass reflex had taken over. It became harder and harder to do acoustic suspension as bass reflex took over. Many(most?) speaker companies buy their drivers from a few main suppliers. And the suppliers build what sells. And bass reflex was what was selling. To get an acoustic suspension woofer you either had to design your own or pay a supplier to build something special for you which, of course, is more costly than standard designs.
And closed box is hard to sell now. It sounds different. Bass reflex sound is what most people have heard and what they think bass sounds like. There are very few closed box designs today. Off the top oif my head there's Magico, a top of the line design. But I don't know if they are acoustic suspension or closed box though I think they use the term acoustic suspension. They use closed box because they know it has less ringing that bass reflex.

