First you need to begin with measuring the drivers for its TS parameters. There are two approaches to crossover design -1. Network analysis (design and analyze what you will get ) 2. Network Synthesis (what you should have in the network to get the required result). Off late i found the network synthesis to be less time consuming and good sounding designs. Also there are parallel and series crossovers. I find series crossovers are better sounding than parallel though they eventually they work the same way.