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

@kevinzoe I took some measurements with DIRAC and a MiniDSP calibrated mic and posted a screen shot in my virtual system. Symmetry doesn't look terrible but I have no idea how bad the peaks and nulls really are.

I can apply the filter to the NODE but obviously not the analogue source. 

If anyone cares to take look and provide an opinion it would be much appreciated. 

Thank you.

@macg19  Thanks for taking the time/effort to take measurements with DIRAC. 

It appears that DIRAC is working as it's expected matching L and R speaker decibels levels as best it can based on whatever parameter limits you set.  But you're on step 4 when steps 1-3 aren't quite finished.  There is a sequence to treating a room and it generally goes like this: (1) begin with Early Reflections and L/R speaker's reflection symmetry within 0-10ms which usually involves 1st order reflections in most domestic sized rooms.  Energy Time Curve data is used for this step which REW provides but I don't know if DIRAC provides.  (2) Bass Decay time should be dealt with next to reduce masking of midrange details when bass decay times are excessive compared to those of mids/highs.  A T30 metric is found within REW and you can get pretty granular by using 1/3rd octave intervals to see where problems lie and what the best type of bass trap is to use (velocity or pressure). Again, not sure DIRAC measures this as it was designed more for frequency response and not the time domain (i.e. early reflections and decay times). (3) Mid/High decay times come next with the use of diffusion and reflection and appropriate T30 decay times suitable for your room size. (4) last comes frequency response and gentle EQ which is where DIRAC lives as I understand it. (I use Audiolense XO for FIR convolution filter creation myself.)  While Frequency Response is usually the default go-to chart to use, it is impacted by the sound bouncing off reflective surfaces between the speaker plane and your listening position.  Because the frequency response's informational content includes the effects of early reflections, it's important to get those locked down first otherwise you're chasing your tail.  Looking at your system picture I am not convinced that the wooden slats on the left sidewall and curtains on the right side are giving you symmetrical early reflected energy especially in the 1 and 2kHz octave regions where our hearing is most sensitive - the wooden slats would preserve the 1 / 2kHz octave energy while the drapes would attenuate it, and I hazard to guess that only through the use of DIRAC are the L/R frequency response curves very similar.  I'd encourage you to try the same type and thickness of absorption panel on each sidewall as a common denominator to different construction materials used for each sidewall which impacts tonal balance.  Play with absorption panel angles and distances from the wall behind it to achieve L/R Early Reflection symmetry before turning on DIRAC.

Reading your DIRAC graph:
> first off, the chart looks like it might be at 1/24th smoothing which shows all the nasty bits, so don't be surprised or discouraged. 
> the curves track each other nicely which is DIRAC's sweet spot but range from about -2 to +8dB for a +-5dB range which should ideally be at +-3dB or better.  Getting the sidewall's 1st order reflections symmetrical should help DIRAC out so that it doesn't boost/cut EQ as much.
> The large "U" shape in the 30 - 80Hz range is trouble as a kick drum lives in the 40-70Hz range as does bass guitar, and other instruments.  The R speaker at 45Hz is about 6dB louder than the L channel - not good. This could be caused by the R speaker being near an external wall with brick/concrete behind the drywall which reinforces these low frequency's energy whereas the L speaker is near an inside wall that is less stiff and flexes. Pressure traps can help here like GIK Scopus T40 / T70 traps as can multiple subwoofers.  Experiment further with speaker / chair positioning to see if that "U" hole can be remedied as it is beyond DIRAC's boosting limits.

@macg19   https://pmamagazine.org/early-reflections-101-the-first-10-milliseconds-that-make-or-break-stereo-imaging/

@kevinzoe - excellent article. Thanks for posting.

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.