Please, don't get me back on tetrahedral
It confuses the hell out of me. And one tetrahedral speaker was the ultimate goal, when I started thinking about this. Fortunately, a friend who designs speakers for a living was able to talk me out of that dream...
The main reason is, you'd have to design the one multi channel speaker with the room it would work in. And it would need to be in the center of the room. The rest is some of Bose's "Direct Reflecting" system. We all know how that sounds.