It is recommended that the wall behind the speakers be reflective in nature, so that the sound develops properly. On the contrary, the wall located behind the listening position should be absorptive, so that the rear reflection of the sound does not interfere with the perception of the stereophonic image.
Weird how you seem to answer your own question.
@avl1947 I agree with you. Absorbion behind the listening position. I'll add that the corners of the front and side walls will often need bass traps or absorbion panels. This not only controls bass, but helps create and shape the soundstage