Knowledge + Compensation circuitry + a good horn = good results to 16khz +

How do you get the "Knowledge" to design the "Compensation Circuitry?"

For example, I have ordered a pair of BMS 4592 2" compression drivers from Bill Martinelli. Say, I want to build a crossover for a speaker using this driver. (I have not studied xo's yet, so please forgive me if I spout newbee nonsense.) How do I know how to design the compensation? Suppose that I am the world's best crossover designer. How do I know what this system needs? Do I look at the specs for the drivers? Do I look at the response graph? Do I measure spl with my meter across the spectrum? Do I listen to the driver before building the crossover? Trial and error: build a crossover and tweak it by swapping components out one or two at a time?