I've been playing around with REW and my basstraps today, to measure the effect.
Well, set up REW, took a few readings of the room as it is now (1M, 8sweeps), and then removed all the acoustics panels I have.
That is one corner trap (60cm face, 85cm tall, one 2'x4'x4" sheet cut in 8), two 4" sheets straddling corners, four 1,5" panels in reflection points and one 1,5" panel straddlign the last corner.
Took a few more sweeps (1M, 8 sweeps again), and overlayed the plots. And they were virtually identical. There was minute differences, most likely due to inaccuracies in the measuring chain, but really minute. I was expecting a dB here and there, at least.
So I started moving things around, placing traps at odd locations, floor to wall corners, opposite corners, basically wherever I could get to. And on a few of the measurements there were slight differences, some in the 0.5dB region, but very little. Are 4" Rockwool THAT ineffective?
The thinner panels that I've used to kill reflections really help, my impulse response tell me that, but the basstraps are really just a waste. Do I just need more? I would think even the three thick panels I have would show up SOMEWHERE on my graphs?
I have another 12 4" sheets on the way, and will make proper tri-traps from them, but I'm having second thoughts now. Might just dress them up and use them as general absorbtion, if they are not gonna do anything to my messed up bassresponse.