Try opening the curtains. Not ideal as on one side but glass is lively (usually bright) vs curtains are damping.
Room treatment
My listening room sounds overly dampened, and I want to look at options for making the sound brighter. The room is 4 meters by 7 meters by 2.75 meters. Two walls are mostly covered with bookcases, and two walls are partially covered by curtained windows. The floor has wall-to-wall carpet. What should I consider?