Wayne Parham Messages: 18787 Registered: January 2001
Illuminati (33rd Degree)
I use air core coils where possible to prevent saturation, but usually use laminated cores for coils larger than 3mH. An air core coil with enough meat to keep DC resistance down is just too large for the higher inductance values. If you look through the crossovers shown in the shopping cart, you'll notice that we put Erse Super-Q coils on some of them.
About resistors, I use a 100 watt part for the Zobel but 10 or 12 watt parts for the other locations. The R1/R2 values are made with a series/parallel network of four resistors to increase thermal limits.
The post below has links about various topics related to some of the things you've brought up such as L-Pads, choice of crossover components, etc.