I just went into the archives and found out that my center is the AX1, if you look on the picture, I guess this speaker was designed to go under a tv

http://www.axiomaudio.com/images/HomeTheater_AX.jpg
it's the speaker at the bottom

I think that I already try to turn it upside down, but I think I had the same problem because of the shape.

I will need something to change the angle or use a shelf that I can adjust the angle.