Room treatments on the ceiling?

I use a ceiling mounted broad band absorber to eliminate first order primary ceiling reflections along with side wall treatments. The ceiling mounted panels help increase soundstage width, depth and dimension.

At what frequencies are you experiencing frequency modes?

Check out Armstrong Ceiling products. They make some fabric that is hung in 'waves', the idea could be a great DIY project to tame your sound waves.

Don't forget Michael Green's Room Tune products, they are very effective!

I don't think you need absorbtion as much as something to "randomly scatter" the ceiling reflections. Absorbtion is removing much of the liveliness of the music by affecting all frequencies-but in no way equally. Try to think of treatments you might like; perhaps add character to the room. Not knowing your ceiling there's nothing to recommend; but, if you tell about it I will offer suggestions.

I use four ASC Cinema Panels, that both absorb and difuse. The effect was helpful in taming an overly bright and bleached sounding room. I have them mounted directly above, and parallel to, the wall behind the speakers. Helpful. We have soffits along the perimeter of the ceiling, so the sound panels are mounted at 45 degree angles -- this helped considerably in the ascetic appearance of the panels.

Ceiling treatment is very effective once you have scattered back wall reflections AND you have carpeted and cleared area in front of speakers. Nuance will become obvious and even prominent. It's essential to get the "real"-subtle" artistic intent. It's the difference between the casual versus "serious'-i.e. "absorbed-sensitive" listener. After I treated my ceiling and floor - I would never go back. Don`t use absorption-keep things lively.

Ptss, what did you do to treat your floor?