I used two to them for greater than one year and feel they are a very valuable addition. I got one at first and used them in the center between my speakers. I was so impressed that I got a second one and placed it behind my listening chair on a bookshelf about three feet behind and above my listening chair. I think of them a resonance control devices that augment bass traps and other resonance control devices.
When I first used one of them I along with some of my listening group kept taking it in and out of the system. Soon all agreed the system sound better with it in. Now, I don't think the system would sound as good without them. To me, they help focus the sound and add a more full-bodied presentation. Hope this helps.
