I have much respect for you turning a barn into a music room. Many folks do not have that opportunity. The fact that you have put esthetics in the design above designing it for the best sound is something you will always have issues fixing imo. Looking at your room design and layout I honestly have difficulty telling you where to start. You obviously love the windows to open out into nature but the right corner with windows on both walls is basically a big reflective area for the right speaker, or the left one if you use the long wall instead as recommended earlier. Personally, the only way to improve your sound in the current room layout is having a professional taking acoustic measurements to optimize the sound as much as the room will allow. Short of that you will be shooting in the dark and I don't think anyone looking at it here can give you any valuable advice short of making major changes. I did build a listening room/building from scratch but sound acoustics was my only concern. Yet it took me a couple years to get the right treatments in the optimum spots. Trial and error. I did start with input from a couple different guys at GIK. It helped but the end product is much different than their original recommendations.
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