What s behind your chair?


Having been the butt of jokes for last week's "What's in front of your chair?" thread, I will once again stick my neck on the chopping block and start a similar thread.

Right now, I have a cloth covered oriental folding screen against the wall 4 ft behind my seat. It definitely helps with imaging compared to a bare wall. However, I am considering putting my floor to ceiling bookcases behind my listening position filled with records, CDs and books. There is enough variation that it should be a pretty good diffuser.

Does anyone have an opinion as to what works best behind'ya: absorbers or diffusers? With what audio specific products have you had great sound? e.g. RPG skyline. How about DIY Tweaks? Let the games begin.
metaphysics
F. Alton Everest ("Sound Studio Construction on a Budget", "The Master Handbook of Acourstics") and Robert Harley ("The Complete Guide to High-End Audio") seem to agree that on front and back walls, diffusion is best. I put an array of four RPG Skyline diffusors on my back wall, and am extremely pleased with the sound. I have DIY designs for imitations, also for RPG's "Omniffusor", which should work about as well as the Skyline--contact me if you're interested and able to cut Styrofoam accurately into "towers". Your bookshelf is a pretty good potential diffusor already: try varying the depth of the books. It might look odd but sound very nice.
Post removed 
When I put two bookcases (about half-filled), one floor-to-ceiling and one 4 ft high, in the back of my home theater room, sound became richer. Putting tube traps in the front corners got rid of the boominess. The room is only 7' x 11', so I didn't expect a big, rich sound, but I pretty much got it.