Ten octaves range for a mechanical transducer that must put several acoustic watts into a medium-sized room is a colossal engineering nightmare. If it must as well disperse the highest frequencies across a horizontal 30° or so, all the worse. Educate yourself. Do the research. Solve the problem for yourself (or not!). Guys with doctorates in this stuff have torn their hair out over this problem.
I'm glad I don't have to solve it; I can just spend a few hundred clams, and pay somebody else to.
Aloha,
Poinz