Windows in a listening room

I used to have a media room in my basement, fantastic  to listen to my  stereo  or watch a movie in 7.1.Now I moved have a town house with cathedral  ceilings and a balcony. The room is like a concert hall,the windows have vertical shades and it's no problem. 

Look at my system’ page. I use a half sheet of (Dacron) hung behind my thin curtain. Low cost, high value. Can't tell it's there.

Marigo large white dots on window and Hunter Douglas fabric vertical blinds is the way to go for best sound. 

Following  geoffkait's advice, I got in touch with Marigo Audio Lab (marigoaudio@frontier.com)  and at Ron Hedrich's  suggestion ordered 4 of his SD-51 Superdots (black, 2" dia), which at $187.20 delivered were not cheap. But I installed them today and they do make an improvement in the room's response. I'm very happy with the result.

A couple of years ago, I changed the four curtains in my room because they let in too much light. The new blackout curtains were made of much heavier materials. It did not occur to me that the new curtains would have an effect on the sound system, but they did. The imaging became more focused and detailed. I thought that the acoustics in this room was damped well. I was very wrong, and it shows that you could never let your guard down. There is always something to upgrade. Damn this hobby.