I cheat....
A digital Xover combined with 2 eqs' with RTA, line or mic.
Use of RT displays of various sorts...again, line or mic'd.
Read the results and apply, tweek as desired.
Since I'm diy-ing drivers, it beats cut 'n try with drivers' known characteristics rendered nil by brutal surgery without painkillers....
...at least, to the mechanism....the surgeon? 🤷♂️🤦♂️😎