If this has ever been done, I apologize. I'm a visual person, so I figured I show some illustrations relating to phase differences between cabs and why mixing cabs can be a bad idea. If you have no idea what any of this means, just enjoy the pics. I used WinISD and LTspice.
This pic shows 3-100Hz sine wave signals. Green is perfectly in phase (consider it the reference). Blue is 60 degrees out of phase relative to green. Red is the sum of the two signals. Notice the reduction in level of the red signal. In theory, two signals that are 180 degrees out of phase with each other will completely cancel out.
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This pic shows a frequency response plot of 4 different ported speaker cabinet concepts:
Yellow = a single 15 cab tuned low
Blue = a more different single 15 cab
Pink = a typical 2-12 cab
Green a typical 4-10 cab
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This pic shows the phase response for the same 4 cabinet concepts:
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Phase plots can be a little strange if you're not used to seeing them. I typically think of the area between 60Hz and 100Hz the "money zone" for bass guitar, so focus on that. Look at the phase differences between these cabs! You may be thinking, hey, none are perfectly in phase! Well, that's a more complicated subject. Speaker cabinets introduce phase shift as well as the speakers themselves--can't be avoided. EQ's mess with the phase as well. We're talking about mixing cabs here, so we're concerned with relative phase to each other.
Anyway, let's pick a frequency...80Hz. 80Hz is close to the second harmonic of a low E string...in other words, money.
Yellow = 58 degrees
Blue = 95 degrees
Pink = 128 degrees
Green = 139 degrees
They are all somewhat out of phase with each other, so they would all have some cancellation when used together. The worst case is Yellow and green, which in this case happens to be a 115 and 410--they are 81 degrees out of phase at 80 Hz. The best case is Pink and Green, which happens to be a 212 and 410--they are 11 degrees out of phase at 80Hz. Those would probably play okay together because the phase between them is consistently not too far off. Check out yellow and blue from 200 to 1K--they are pretty much perfectly in phase in that range. Down low, not so much.
Anyway, think about the first pic that shows a 60 degree cancellation. If you pick any two of the phase plots at a given frequency, you can probably imagine the resulting signal loss.