I'm about to share with you guys a very interesting experiment.
I started treating my room about a week ago. Someone (a friend of mine locally) told me to make bass traps using R-30. They come in 4" wide. He asked me to double them and cover from floor to ceiling. So I made two bass traps 8" thick each. Before I installed them, anther friend (from forum) told me to cover all the area behind my acoustically transparent screen (Left/Right/Ceiling) with 1" thick LinAccoustic material and then add 6mm plastic (I can't remember the exact name) and then add another layer of LinAccoustic (basically a sandwich of LinAccoustic with that plastic in b/w). So I went a head and did that. Then I added bass traps.
Now these being in place, I started taking reading and I could see good result that I shared with you guys in some previous posts. But there was this nasty dip around 80-90. I couldn't figure out the reason. I moved speakers all around but that won't go. Then I though, what if these bass traps are causing it. I took them out and took reading. Wallaaa. That dip is gone. Well what about decay then???? Compared water fall with/without bass traps and no difference.
So basically these R-30 8" bass traps were trapping 80-90 :-). Lesson learned: Don't over treat your room :-) Thanks to REW, it was much easier to spot it. Here are the graphs to show the difference.