Your 4 Pi's look great in RED!
But it looks like you don't have bass ports in your speakers, at least they are not visible from damping material, could this be the reason for bass problems?
I think what he is getting at is this.
Isn't the port supposed to be a boxed in area "X" amount of inches deep into the speaker cabinet? It looks as though you just created the opening instead of boxing it in. But as he stated perhaps you filled in the boxed area with damping material.