Lately, I come across the resonators and diffuser products by A.S.I. (a French company). Its products are ‘miracle’ add-on to any room which reduces/balances the room’s acoustics and audio vibrations. One can start with their one diffuser and 17 Sugarcubes and you will hear the immediate effect.
The diffuser in the middle of the wall dictates where the vocal focus be, and the 17 Sugarcubes act like a passive equaliser to tune the highs, mids, low mids, and lows.
With the above Silver Resonator installed, the sound image is huge and music sounded nice throughout the house.
I have three Sugarcubes installed on the balcony window behind my listening area. They tuned in the soundstage better.
Yes, initially I was skeptical and find them sounded like snake oil products. But they really work! Go check them out.