Any thoughts about the RR-888

I've been using two for about 4 years, a little below tweeter height, and I like the effect. It seems to calm and clarify to me.

I’ve been using two Schuman resonators (one atop each speaker) and a box of Synergistic Research HFTs strategically placed around my listening room for years. I had serious doubts regarding the effectiveness of the HFTs since my listening room is heavily treated. I am glad that I was wrong. Still use a FEQ as well.

I’ve tried many tweaks through the years.

Thanks for all the info. Really appreciated. 

Do two make any difference vs one? When you operate two, are they connected in some way as to be in phase with each other? If they are in phase, does that matter, and how? Is this a subsonic "noise" reduction system?

For a few years, I’ve had a pair in a 3000 cubic ft sound treated room. Their positive impact is on the size of the sound stage — not the SQ. It’s subtle but genuine to me. Best detected by listening with the resonators off vs on. They’re mounted in corners on a horizontal plane projecting several feet above my listening spot. I would purchase them again, but after addressing more pedestrian issues like speaker position.