My guess is you need to balance out your room. It's not only high frequencies giving you fits. It's reflections and a frequency imbalance within the two sides of your room. When you select curtains look for natural materials opposed to synthetic materials. Synthetics are frequency selective and natural materials will give you a more balanced sound. What's the other side of your room like?
Curtains to control high frequency
One wall of my room is glass and I am about to install curtains over it to deaden high frequency reflections.
My question is, if the curtain fabric is relatively open weave linen and I am having them lined with a lightweight baby blanket type material, do you recommend one later of the lightweight lining, or two layers of the lining?
Thanks,
Shaq