In the search for figuring out what the Cab DEP really do, I had to first find an amp with flat frequency response. Then I had to pick the flattest amp and measure it with the cabs to see which ones has the smoothest frequency response (such as it is). That data is given here. Next I will measure the smoothest cab with the various mics to see what will give me the cleanest platform on which to look at the cab DEP parameters. All this because I don't know what to expect from the cab DEP parameters.
I picked the 121 Ribbon to test the cabs because according to the mics' technical sheets that one seems to have the widest and flattest frequency response. I picked the Class A-15 because that also gave me a flat frequency response when adjusted.
The frequency responses of the cabs can be found in the PDF attached to this message. The Excel sheet containing the data can be found here.
What to do with this? Not really sure how helpful it is, but it appears the single driver have flatter frequency response than multi-driver cabs. If you want a brighter sound, go with the single driver cabs. I figured as long as I took the data I may as well share it.
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Edit: the file is too big (241k?). You'll have to download it from here.
Edit: corrected the link above (again).