tomthiel - thank you for our interest.
Height of my room is about 7.9 ft (2.4m). The measurement of the part of the room with the speakers is more exactly 12.8 x 13.7 ft. (3.9x4.2m). Speakers are standing on the long side of this room, behind them is a huge glass window. Now there is only a thin curtain seperating the speakers from the glass wall but I'm thinking of adding more sound absorbant blinds. The whole room is larger, it opens up to larger dining and kitchen area on the small side, in total more than triple the size. Changing the position of couch or shelfes is not an option.
Here ist a picture of the situation (with cats:) Any thougths on how I might improve things? Thanks a lot!