Argent Room Lens. These are Helmholtz Resonators that are used adjacent to and i between loudspeaker to enhance imaging, spatiality and dimensionality. Although there are thees room lenses one for each speaker and one for in between.
According to Soundstage!:
In my room, the most noticeable improvement is in how much more real the space in the soundstage seems. There’s no more width or depth than before, but now it is simply more real. You’ve perhaps heard people talk about soundstages that seem so real you think you can get up and walk around between the musicians… that’s what I got using the Room Lenses. After you get over the initial goose bumps and giggles this wonderful soundstage provides, you begin to notice other things. That little lumpy area in the bass? It isn’t lumpy any more. That recording where the harp just kind of sits there… now you hear small inflections in the playing and the full measure of the harp’s shimmer. Those cool drums? Whoa! Now there’s an actual vibrating head/skin on the drum and you hear it very clearly after the initial whack. Even on recordings where I could already hear the drum head/skin after the whack, the improvement in tonality whas such that the tuning and tautness of the head/skin were evident. No matter how great you think your system is at making realistic "space", you won’t hear how good it really is till you get 3 Room Lenses in your room and position them correctly.