Alexc hits a good point. If you don't have absorptive material at your first reflection points, you are smearing your image pretty bad. This is not a big problem if you have your speakers on a long wall. I had mine set up on a 20 foot wall and my lateral imaging was good. When I went to the 14 foot wall in the same room, I had problems. Sound absorbers, drapes, etc at the first reflections points, really made a big difference in this case.
To find your first reflection points, hold a flashlight or laser pointer at the top of your speaker and shine it on the side walls while someone else holds a mirror flat against the wall. Adjust the flashlight and mirror until the reflection hits your listening position where your head would be. Now, mark the spot where the mirror is at. Do this for both speakers. Then do an experiment of listening to some very familiar music without any absorption and then again with some type of blankets, absorbers, drapes, etc. You should be amazed at the difference.
To find your first reflection points, hold a flashlight or laser pointer at the top of your speaker and shine it on the side walls while someone else holds a mirror flat against the wall. Adjust the flashlight and mirror until the reflection hits your listening position where your head would be. Now, mark the spot where the mirror is at. Do this for both speakers. Then do an experiment of listening to some very familiar music without any absorption and then again with some type of blankets, absorbers, drapes, etc. You should be amazed at the difference.