Update...
Running some sweeps with both woofers disconnected approximates the midrange crossover around 500Hz.
BTW,
Spectroid for Android phones is a killer app when you need to do some down-and-dirty on the spot. Highly recommended!
I did some rough math from measuring the cabinet internals. I didn't account for bracing or crossovers, but I did approximate the volume of the midrange tube and subtract that. I came up with a net 1.15 cubic feet for the lower chamber and .73 for the upper.
I plugged my numbers into a
port tuning calculator with the 3"Ø x 5" port and got a tuning frequency of 48Hz. To confirm, I did the "salt test" and got an actual 46Hz, so my math wasn't far off.
My conclusion from all this is that the only way forward with these speakers is to make them a 3-way and somehow cut out that divider, so both woofers can breathe. That sealed space is a hindrance. Will also have to replace the woofers with 8-ohm drivers that would perform well in that expanded space (and connect them parallel). Modeling the full 1.88 cubic feet gave a 37-38Hz tuning frequency. The results will be interesting. From the start I've not wanted to modify the cabinets but I have no affordable options left.
So with a 3-day weekend coming up and having the house to myself for most of it, the desecration shall soon commence!