Originally Posted by mczx
Can you list what treatment you did, the cost and if any measurements were done pre and post? How would you describe the improvement if no measurements were done?
The room had horrible flutter echo, so dealing with that was the first order of business, just to be able to hear what the next worst problem was. So I threw up a bunch of home-made tube traps that were later replaced with broadband absorbers covered with slats.
The room was measured numerous times during the process. Most of the empty-room modal behavior looked predictable and the stuff that didn't make sense may have been due to the room having a cathedral ceiling. It was ~9' tall at the back wall, rising to a bit over 11' at the peak, then down to ~10' at the front wall. The room had a really long decay when measured empty, possibly due to the cement floor and rigid walls, with no windows on the long walls, none on the front wall and only a metal door on the back wall.
Eventually, the front wall was treated to about 80% coverage with deep broadband traps. A cloud was hung and it probably had too much absorption initially. The home-made tube traps were redistributed and the room was getting fairly dead but was sounding much better. At this point, we did some extensive testing and found that a mode in the ~45Hz range was the major LF problem. The owner wanted a couple of Helmholtz absorbers built, so I built a couple that were ~30 cubic feet each. Those had little effect on the mode, so next I built two that were about 200 cubic feet each and spent much more time fiddling with the tuning and eventually, they did the trick. We spent quite a bit of time working on rear wall diffusion at that point and people started smiling.
I then tweaked by adding slats to about 60% coverage on the broadband traps and ~40% on the cloud. Additional devices (abfusor style) were built to go behind the monitors as a final tweak. Unfortunately, I no longer have any of the photos or measurement data. The PC I had them on was killed by a lightning strike and the only other copy was deleted when the owner sold the property. The waterfalls looked good but I don't think they would blow you away. Likewise, the ETC was nothing to write home about but no major problems were seen in it.