Thanks to all for great comments!
The room is small, 18 sq.m (6 x 3m), the ceiling is approx. 2.7 m high. The speakers are placed approx. 2.5 meters from the short wall against the draped window. They have a radiating back panel, but the back grille is not removed. You may see their pic at www.nightingale.it. To check the HF driver is a good idea, for which purpose I have to unscrew the driver. Duke's and Herman's recommendations to deal with disperson instead of absoption make me feel that these speakers were better suited for my old apartment (which was brighter and less absorptive than the present one). I will explore this further. Anyway, I am waiting for new speakers to arrive.