Interesting topic to me….I was not one of the naysayers who actually experimented with @mahgister bottle Helmholtz resonators. I liked using 4 - 1.75L Bourbon or other bottles with long necks. More is better but I had to control myself. I added 1-2 inches of water, drilled holes in the caps and inserted various sizes (2-4 inches various diameters as well) of straws through the holes with a tight fit. Set them up about halfway between the system and sitting position on an arc. 2 between the speakers and 1 outside of both speakers. As crazy as this sounds it filled the room with a fuller more 3D sound bringing the music further into the room. It is a subtle improvement in my environment. I only use 4 bottles so I can easy pull them out when I want to use them and no one is around. My reputation to a hit when people saw Bourbon bottles spread throughout the room with straws in them. 🤣
Fun experiment. Thanks Mahgister👍