The design of the first cross-over is done. The target is an acoustic 4th order Linkwitz-Riley at 2500 Hz. My simulated target responses using measurement data taken using a ground plane at 72″ is on the top (the data is not measured with crossover network, it is measured then a crossover simulated). The bottom plot is based on a simulation of the drivers + crossover (which is why it is so smooth).
The electrical network is shown below. Electrically the tweeter slope is 2nd order, and the mid-range unit crossover 3rd order transitioning to 2nd order (that is what the 1.5 ohm resistor does connected in series with the 18 uF cap). Zobels are used on the mid-ranges. Zobels are even on the mid-ranges before and after the 1/2-way cross-over inductor. (Note shown: the capacitor value is 45 uF in series with 7 ohms for the Zobel to the left of the 1.8 mH inductor.) The Vifa D27SG-05-06 has a faster high frequency roll-off than similar tweeters. To compensate, the attenuation resistor is by-passed with a 15 uF capacitor.