I have 6 in total, 1 on the wall directly in front of me, 2 at the first reflection point of the speakers. 1 directly behind me and 2 more on either side of me where i sit. In my room, what they did was make the soundstage wider and more pronounced. they separated the instruments more if you will. I am hearing acoustic guitars and snare drums more focused off to the sides. It sounds like i am surrounded now, and that the stage has disappeared. It is hard for me to explain as i may not know all the correct terminology. I just know that there was a significant improvement.
Now i also tried them in the basement on my second system, and there was no change that i could hear at all. So each room will be different. The dealer i bought them from was surprised with that. lol