acoustic system resonators

Audiofeil, I get the impression that you never did hear these resonators yourself. It's very easy to convince a listener with an open mind, that these resonators work. If this person is willing to pay the rather steep price, that's another question.

Tbg,
The back wall is behind the speakers indeed.
The cups should be resonating freely, standing on their wooden bases, and the surface they are attached to doesn't matter. The position of the resonator in the room (in relation to speakers and listener) has far more influence.

These resonators are not cheap, but they work !
The discussion how they work and which audible effects they should or can have is quite interesting, but you only can trust your own ears.

There are guide-rules for placement (eight steps):
1. Position a resonator on the back wall, exactly between the speakers, 30-60cm above the tweeters
2. Position a resonator above the first one (between this and the ceiling)
3. Position a Basic resonator right under the first one, around 15cm above the floor
4. Position two Silver resonators on the side walls, next to the speakers, same height as #2
5. Position two Silver resonators on the side walls, next to the speakers, 15-40cm above the floor
6. Position two resonators on the side walls, same height as #1, next to or slightly in front of the listening position
7. Position a resonator right behind the listener, same height as #6
8. Position a Basic resonator right behind the listener, 15cm above the floor

I'm using:
#1=Platinum
#2=Special Gold
#6=Special Gold
#7=Special Gold

When I remove all cups (and I have showed this to a few audio-friends) the soundstage collapses completely (in width, depth and height).