You could measure the depth of the high frequency driver in relation the mid driver and get a number that would maybe, kind of, sorta be a start.
Using SMAART or REW (that is free) you can dial it in, measure from on and off axis.
Did OAP have any published DSP settings?
Assuming the the drivers are all wired and operating positive forward flip the polarity of the high driver, adjust the processor mid out delay till you get the deepest notch in the response, flip the polarity back to normal.
Do that with no EQ applied anywhere.
A very crude way to do that with no equipment other than your ears would be to do the polarity flip, use a sine wave at the frequency of the intended crossover, set each band pass output so they are the same level, then turn in this case the mids and highs both on,
set yourself in the sweet spot a few feet in front of the speaker and while adjusting the mid delay listen for the deepest cancellation of the sine wave tone, flip polarity back to normal.
You may want to play around with unlapping the crossovers frequencies and look
at the phase and frequency response.
As example 1774hz for the high frequency high pass and 1600hz for the mids low pass
and so on across the other band passes.
