Outlier - nice name! You into statistical analysis by chance? I digress . . .
You mention ceiling corners and there's lots of fiberglass-type absorption products you can use, just be sure to leave a healthy (6"+) air space between the wall surface and rear of the absorber so that it works across a broad freq spectrum and doesn't act as a low pass filter which would throw off the timbral balance of the reflections and reflections of those reflections.
Have you considered a hemi-cylindrical diffuser (often called polyfusers or polys for short) for the floor-to-ceiling corner? They're made from Sonotubes used at construction sites for concrete pouring. If you use a 180degree arc then it'll diffuse in about 120 degree pattern and you can stuff the interior with OC701 or 703 fiberglass to act as a bass trap. The curved surface facing into the room should be hard enough to prevent absorption of mid and high frequencies. Use a radius with a minimum of 12" (24" diameter) and finish it off with some kind of Guilford or Maine cloth or what I did with stained wooden veneer:
http://i1126.photobucket.com/albums/l620/kevinzoe/Frontwallhemi-1.jpg
Match the wooden veneer to your speaker's or fireplace bricks or wall colour etc etc. Just a thought and hope it works for you.
You mention ceiling corners and there's lots of fiberglass-type absorption products you can use, just be sure to leave a healthy (6"+) air space between the wall surface and rear of the absorber so that it works across a broad freq spectrum and doesn't act as a low pass filter which would throw off the timbral balance of the reflections and reflections of those reflections.
Have you considered a hemi-cylindrical diffuser (often called polyfusers or polys for short) for the floor-to-ceiling corner? They're made from Sonotubes used at construction sites for concrete pouring. If you use a 180degree arc then it'll diffuse in about 120 degree pattern and you can stuff the interior with OC701 or 703 fiberglass to act as a bass trap. The curved surface facing into the room should be hard enough to prevent absorption of mid and high frequencies. Use a radius with a minimum of 12" (24" diameter) and finish it off with some kind of Guilford or Maine cloth or what I did with stained wooden veneer:
http://i1126.photobucket.com/albums/l620/kevinzoe/Frontwallhemi-1.jpg
Match the wooden veneer to your speaker's or fireplace bricks or wall colour etc etc. Just a thought and hope it works for you.