Thanks folks for the comments so far. Some interesting possibilities. Just to mention, while I can put some absorbtion material on one of the side walls, it won't be symetrical with the listening position and the speakers (they will need to be closer to the listening position, as there is a corridor in that area of the side wall). Also, the other wall is all glass door, with curtains between. I could attach the material to the appropriate part of the curtains, but that seems like stretching things a little. I guess I could try the ceiling as well.
Overall, from what I've heard it really seems like the panels have only deadened the sound - I somehow have my doubts about any benefit they're going to offer. I'll try removing them from behind the speaker, and then maybe try the opposite as well. I'll also try removing them and adding more to certain areas. It still seems like a big confusing mystery though. I wonder would the addition of some highly reflective surfaces (rather than absorbant surfaces) made a positive difference. Cheers,
Outlier
Overall, from what I've heard it really seems like the panels have only deadened the sound - I somehow have my doubts about any benefit they're going to offer. I'll try removing them from behind the speaker, and then maybe try the opposite as well. I'll also try removing them and adding more to certain areas. It still seems like a big confusing mystery though. I wonder would the addition of some highly reflective surfaces (rather than absorbant surfaces) made a positive difference. Cheers,
Outlier