I ran some additional tests using individual "cells" with the same target frequency as my boxes. I thought this might help show whether the lack of division between cells in the large boxes was having an impact.
I built one small cell, with a depth of 7.25" and inner dimensions of 4x4". The front face of the the cell had a single hole of 1/4" diameter, making it equivalent to the cells of my larger units.
I also built a second cell, with a depth of 12", inner dimensions of 4x4", and a single hole of 11/32". This hole size was indicated by my adaptation of Cox's Matlab as giving a roughly equivalent resonant frequency of 42Hz.
Finally I also included my trusty soda bottle (200Hz) in the testing. Here are all the contestants lined up:
First I did the candle test on the two mini-cells, and they both appeared to resonate at around the right frequency (I used the frequency sweep function in REW).
Next, I made some REW measurements with the resonator mouths facing my left main monitor (I bypassed the sub and right monitor - the mains can do 40Hz no problem). The mic was positioned close to the mouth of each resonator, like this:
The tests also included a run with one of the mini-cells flipped around to present its back (hole-less) face to the mic. Consistent with my past observations, the small low-frequency resonator cells did not appear to do anything to the sound field picked up by the mic:
However, you will note that the trace for the soda bottle (which was empty in this test) does show a pronounced resonance effect at 200Hz. It's cool because you can really see the phase reversal effect that Glenn talked about (from when the imaginary part of the impedance passes through zero at resonance).
So all of the resonators have been demonstrated to resonate around the right frequency, either by the candle test (for the boxes) or simply by blowing on the mouth of the bottle. However, the low frequency resonators differ from the bottle in having no measurable effect on sound levels.
One point that may be relevant is that only the low frequency boxes are able to move the candle flame. The soda bottle does not seem to have any effect on the candle, even though it audibly resonates and has an obvious effect on the local sound field. Perhaps this is due to the pressure levels and/or hole size.
Of course I will also run tests varying the amount of absorbent material in the mini-cells, which is a lot easier to do in these (with cotton balls) than in the full-scale boxes. Stay tuned...