Originally Posted by Lupo
Add and remove the absorber and get used to difference in sound. Without absorber, there'll be a flanger and it'll move up and down in frequency as you move your head closer or farther away. With absorber in place, the flanger should ideally be totally inaudible. Measurements are better but it's possible to use the ear for a coarse indication.
Hey, the flanger test worked great. Without the foam, lots of high frequency comb filtering/flanging as I moved my head. When I put the foam back up, the overall flanging effect diminished by about 70%, and resided mostly in lower frequencies. The ultra high end was completely cool.
So this tells me that the concept is good, but to go with a denser absorber, like 2" 703 or 705 and make it a little larger.
What's astounding is how extreme the comb filtering is without any treatment.
Thanks again for this most excellent suggestion, which I should have tried years ago.
Now I have to go test some different pencils.