Room Treatment? How important is it to treat the wall behind/between the speakers?

I have not used available Software to create the management of Sound within my room, it is carried out using different configurations for absorbent and reflective materials.

The placement of materials used is now concluded and having Triangle Shaped Absorbent Materials in all Room Corners is a must have in my room.

This set up has a Absorbent used behind each Speaker.

Rockwool with a Mass of 35Kg / m3 and used at 100mm (4") Depth is an affective  absorbent and a very cost effective method. It is good practice to create a small dimension cavity between inner face of Rockwool and the Rooms Wall. 

@macg19,

You can see updated pictures of my room in my profile now.

Long story on how to deal with the window... First thing I did was to use REW real time analyzer data/graphs (using the MiniDSP calibrated mic) to see where the resonant points of the room were when I played  low frequencies that I would hear the clear "booms" from the listening position. Just play the tones you want and walk through the room with the mic and find them while you are using the RTA or a SPL meter calibrated with C curve (A curve will not tell you true response for bass). Room bass nodes were partially located in the 4 room corners walls, from floor to ceiling, but they were much more concentrated inside the back sides of the closet - almost up to15db higher than in the listening position. So, I started to investigate what type of bass absorber was the best for the buck and ended using the Acoustic Fields designs. Worked like a charm... I made them as big as I could to fit the available space of the closet without tearing it apart. To make it happen, I had to repurpose the fractal diffuser that was inside the closet and moved it to the right-side wall and the small one from the right wall I originally had I moved to the window side. I did not want to remove the window, so what I did was to use a technique they use in mixing studios where they use portable treatment to control their recordings. I build a pair of sawhorses and created a support for my small fractal diffuser.

The bass traps significantly improved the entire bass response of the room because I could better integrate the subs with the main speakers using crossover & volume adjustments while maintaining a better response of the bass. With the 4 bass absorbers in place, I was able to lower the response of the room around ~35Hz by about 6db. Repurposing the two fractals, I also eliminated the problem of the window, since I eliminated the first reflection problems from both speakers adjusting the position of the middle of the diffuser height to the listening position. Soundstage got more precise and expanded to the sides of both speakers.

You can use a mirror to find first reflection points. Just ask someone to hold it in the wall and move it until you see the mid driver/tweeter – just pay attention to which speaker you are seeing... That is the area where you need to treat for first reflections. Same is true for ceiling and floor.

Hope this helps answers your question.

@kellerjr01 Thanks for posting the pic - you put a lot of time and effort into the room.

A couple of quick points. The DIRAC graph is the measured (uncorrected) response. 

Also I used the room calculator posted above to check the location of the side wall first reflections. I had originally used a mirror. The calculator and the mirror are in agreement. 

I’ll found the cable I need to connect my laptop to the system to generate test tones from REW and I have a MiniDSP mic. I'll work on figuring out how to use REW next. 

My take:  This is an are which benefits strongly from a mix of diffusion and absorption depending on the speakers.  

Diffusors between the speakers and to the sides both enhance imaging and sense of acoustic space.   If not possible, then treat with a light touch. 

The ceiling between the listener and speakers however is a real good candidate that is often overlooked. 

I have a 13x23 ft purpose built room with rockwool behind all walls and acoustimat "rubber" on all walls and ceiling too (under the sheetrock of course). The room is acoustically tight and relatively sound proof so even listening loud it doesn't transmit to other parts of the house. I have GIK treatment too- diffusors for first and second reflections on the sidewalls and bass traps in each front (behind the main speakers) corners as well as in the rear. I'd add them to the front corners, bass "pools" up there and can add boom or muddy sounds.