Window Treatments to Remove reflected sound


I have a listening room with hard wood floors, two French doors beside one speaker, two more across the room and two walls full of windows. Any thoughts on the best window treatment to improve sound? I'm assuming metal blinds are just as bad as the glass and am considering cellular blinds, which seem to be made of polysester but have an air pocket in the middle. Any experience on what works best? Thanks for the input
ruhl