[gotmikey]

I have a room with an attic directly above.  Would I get acceptable absorption at the ceiling first reflection if I cut a square hole in the ceiling drywall between the joists around 24 inches long, and cover them with a framed piece of GOM or other acoustically transparent material?  That way the sound would travel through the first reflection point and get absorbed by the attic and insulation?  If it does indeed work, it would be very easy to do yet be aesthetic.  

Haven't been here in awhile, but I'd figure I'd ask those who know what they're talking about.  

[Russell Dawkins]

I would say it would work, but you had better be sure that you are happy with your speaker and listening positions! Heat will escape up into the attic, if that's a concern and attic noises, if there are any, will be allowed into the room. It seems kind of irreversible compared to absorption.
-Russell

[gotmikey]

I hear you on the listening position, but with regard to heat, I could throw a piece of r19 or some other insualtion on top of the GOM and it would still work.  What do you think?

[Russell Dawkins]

I still think I would surround the piece(s) of r19 with plastic sheet (on the attic side) and seal the edges to the joists to prevent actual air movement through, no matter how slow. You would get your MF and HF absorption as if this were mounted on the ceiling, but better.

[JLM]

I don't like this idea:

Attics are hot/cold, humid places that can contain all sorts of vermin.  Three good reasons to maintain an effective barrier between living and attic spaces.

Can you know what frequencies will be absorbed?  Seems like a crap shoot to me.

The rest of the frequency spectrum that's not absorbed will pass back and forth from attic to room and in effect will turn the attic into a resonator.  This happens with rooms built over crawl spaces and has resulted in 20 dB peaks and nulls.