Room treatments behind or between speakers?

Tboooe,
If you have already purchased the room treatments, then I think you should try it out in both the places:
1. between the speakers on the wall behind
2. directly behind the speakers on the wall behind

Chances are you will most likely choose option 1. This is what "locked" down the center image in my case. My room being small, the center of the wall behind the speakers was reflecting a hell lot of sound. Once I put the absorption panels in there the images became very stable.

So indirectly, I guess, the answer is - it depends a lot on your room. Good luck!

Tboooe,
You are welcome.
If your rear is open to the family room, then reflections on the wall behind your speakers should not be as big a concern as it was in my case. You probably also want to think of speaker re-positioning or nearfield listening.

Ghousthouse,
I know what discussion you are talking about. That discussion was based on the Floyd Toole's book - "Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms".
So, a lot depends on the room. What worked for me, might not work for others. I purchased the panels and played with the positioning. That is how I arrived at the current setup. When I started this system, I used to have a tube TV between the speakers. That was the worst setup. Someone suggested a blanket on the TV. It was a big improvement in imaging. Further reading indicated that anything flat and smooth between speakers is horrendous for the sound. With my current setup, there is nothing really flat. Sound breaks up on the equipment stand and gets absorbed because of the panel. I am pretty happy with the setup.
I am thinking of moving my equipment to the basement downstairs after re-doing an area specifically for this hobby.