This is not necessarily the "best" accoustic solution, but it does have some advantages. Behind the listening position in my rental apartment is a standard two-panel sliding glass door that leads to a balcony. The landlord furnishes apartment-grade, hard plastic vertical blinds, each blind being about 4" wide. I simply set the blinds at a 45 degree angle to the room. In theory, sound waves hitting the slanted blinds will reflect at various angles, depending upon the angle of attack. A few will bounce back into the room, but most will reflect into adjoining blinds or to the glass behind and then reflect into the back side of the other blinds.
Does it work? Aside from the sliding glass doors, my room leans toward the bright side, but I don't experience any noticeable listener fatigue, muddy textures, compressed soundstage or confused imaging.
One advantage of slanting blinds, as opposed to draperies or shades, is that you don't have to banish sunlight during daytime listening. Of course, slanted blinds will work even better when they are made of wood or are covered with fabric. And if outside noise is also a concern, thick draperies or black-out shades would be preferable.
