Basically the benefit is how much the "room has got out of the way". Sound seems cleaner and tighter throughout the whole range, and everything sounds cleare. Imaging is definitely better - wider, deeper, more precise. Interestingly, things sound much improved well away from the listening seat, and even in other rooms. Moving away from the sweet spot means you lose the imaging, but the sense of instruments and voices as specific presences with their own space remains. Volume seems up slightly - an effect of improved diffusion? - and doesn't seem to attenuate as much in other rooms as I remember. Maybe this effect is partly psychological and associated with the increase in clarity.

While female voices are improved, the big improvement is in male voices which tend to sound lighter and diction is definitely much clearer. I suspect this is an effect of absorption at room modes.

I've tried experimenting with placement but haven't too much to report. I've only been playing with the 2 near the speakers and working with either interrupting the path from the speaker to the near reflection point, or the path from the near reflection point to the listening point. Results are very similar. In terms of placement with minimal impact on room area, I seem to have gravitated to placing them between the speaker and the near reflection point, but closer to the wall than the speaker. I stand at the reflection point and place the lens between me and the speaker so that the line of the direct sound path would pass between the 2 tubes closest to the wall, and then rotate the unit around the tube closest to the wall until I can't see the speaker through the gaps between the tubes. The lens is then at close to right angles to the wall and casts a first path "sonic shadow" from just before the early reflection point to well past it. I suspect the majority of the direct sound reflected goes to the side wall beside and behind the speaker from whence it is reflected to the back wall behind the speakers. This isn't the placement recommended by Argent but it seems to work quite well and the lens isn't in a visually dominating area right next to the speaker.

My one problem is with stability. I don't have a weighted base the way I built them - the tubes are essentially free standing and very light. I'm trying to think of a simple solution that is within my competence to construct. They're essentially stable if untouched but fall over easily if shaken (eg by large dog padding by) and it takes a bit of juggling to get them to balance properly when re-erected. I'd recommend making some form of wooden non-resonant base with outrigger supports for those with the skills to do so.

David Aiken