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

@macg19   Sure, I can do the analysis for you.  Let's communicate via PM so that you can tell me what you're after and I can advise you on which measurements to take, how to take them, what file format to send to me and I can return a custom Report with additional charts and analysis that REW doesn't provide, including type and placement of treatment recommendations.  Send me a PM if interested.

@kevinzoe 

Thank you Kevin for the very kind offer. I will send a PM when ready. I have a few things to get done before taking measurements and looking at next steps.

I experimented a lot over the weekend and Monday moving around speakers, acoustic panels/blocks as well as the listening position.

NOTE: I know a single frequency response measurement form DIRAC doesn’t tell the whole story but my goal at the moment is to try and get some L/R symmetry and get rid of extreme peaks and nulls.

I took down the RockWool-stuffed painting and the room sounded terrible, harsh, so it was doing something positive albeit likely not ideal.

So I decided to order another pair of 24x46 GIK Wood Slat panels for the side wall as an interim (cheap) solution and moved the existing ones to the front wall behind and between the speakers and I installed a 24x48x2 absorption panel at the first reflection point on the left wall in their place until the wood slats arrive.

This made a big difference – the harsh glare went away and the sound stage was better, for example in terms of vocals being deeper in the stage and instruments arranged in various locations on the sound stage. 

I also moved the 4 Sound Blocks around in every configuration imaginable, and they made almost no difference to the DIRAC frequency response measurements except when I stacked all 4 (2x2) on the right wall about 8ft from the front wall. This helped the 59-60Hz null but they look ridiculous.

Ultimately, I was able to get almost the same effect by moving the primary listing/measuring position forward a foot or so, so that it is under the 8ft ceiling rather than under the vaulted ceiling behind the listening position and moved the speakers back a bit as well.

Here is what I learned:

1. The answer to my original question is YES!!!
2. Installing additional acoustic treatments to treat low lower frequencies without a plan based on measurements is a crap shoot.  

So next step is install the slat diffusers on the left side wall and then take some REW measurements.      

@macg19   Kudos on all the effort and combinations and permutations of treatment placement!!!  Lots of move->listen->measure cycles I’m sure.

Just a note about the 4 Sound Blocks not seemingly made any difference to the DIRAC frequency response measurement (with the 1 exception that looked ridiculous), for peaks/nulls below about 100Hz you’re better off using GIK Scopus T100/T70/T40 membrane traps and several of them as they’re just 2’ x 2’ in size (depth varies) - the Scopus T40 and T70 should improve your 59-60Hz woes when placed against a wall that has an exterior brick/block/concrete backing behind the drywall, in other words exterior wall, and also when placed near the sound source (speakers, sub)..  On the other hand, the Sound Blocks likely affected (reduced) the decay times of the frequencies they affect which REW’s RT60 decay time chart (but look at the T30 metric, or Waterfall chart ) would show and which DIRAC won’t show.  If your mids/highs are being absorbed by the curtains on the right sidewall, then equal absorption on the left sidewall should provide the L/R symmetry you seek.  Another way to approach it is to use an angled board on the left sidewall to redirect the reflections past your head to mimic the absorption the curtains provide.  

Thanks @kevinzoe I'm looking forward to getting some help with the REW stuff but in the meantime thankyou very much for all the suggestions and support.

2 other take away’s

1. There is significantly more agreement on this thread/subject of acoustics vs the many, many power cable threads (I am NOT a cable denier which should be evident from my virtual system, cables matter)

2. Anyone thinking about improving sound quality in an untreated room by swapping cables (or other tweaks) should pause and look hard at acoustics first