i think the idea is that with hangers, if they are all the same, they resonate in sympathy and that is the key ingredient. in other words, calculations for each individual absorber are no longer valid. the hangers used with effectiveness were not very heavy individually, made out of something like paperboard which shouldn't be able to do squat for absorbing bass frequencies. but with a whole bunch of them, a giant sympathetic resonator was created....almost something like one of those experiments in elementary school physics where if you hold one tuning fork near a second tuning fork the second tuning fork will being to ring too, actually, just like that. of course, you are right though...without more data...it is just a wild theory. but, there seems to have been something at work, that was effective, and not completely understood, so may be worth investigating. one cool thing is that the tuning could be adjusted by added more resonators, but i'm not sure what the math looks like.