I have a friend that has these large JBL speakers with horns. The room he has them in isn't very big so he has them against the wall but he has an absorption panel about the size of the speaker, four inches thick, more or less, set on the back. Basically, it is the wall, the absorption panel, and then the JBL speaker, a sandwich. Is this something worth doing?  My friend says it works wonders to control bass and I have to admit music sounds damn fine on his system, even when he cranks it loud, no distortion.  At least no distortion detected from a set of amateur ears.

Is this a valid setup?