sbir

I am a bit confused about this so I need some guidance. Most documentation says you need to keep your speakers a certain distance from the wall. However, it doesn't specify whether the distance is measured from the rear of the speaker or the front. For example, I have the Revel F208...

I have towers that are 4' tall. I had some leftover fabric and built four 2'x2'x4" absorbers which I plan to put on the front wall behind the speaker. My question is how high/low do I put them? I was thinking about having one extend 15" above the speaker then 9" below and then I'm wondering...