I am all for experimentation first. In my own setup, I went with a panel that uses absorption on the sides and a small hard diffuser in the center. This worked well for me.
A friend has a room that was designed by Rives. It has a very large, convex, curved, hardwood diffuser centered between the speakers.
A friend has a room that was designed by Rives. It has a very large, convex, curved, hardwood diffuser centered between the speakers.