Setting the crossover frequency is definitely a little black magic. If you look in the manual for the ICBM it recommends that you take the +/- 3dB rated frequency range add 10HZ to the low end and set the crossover there or higher. (At least I think that I remember reading it in there.)

For example I have a pair of speakers rated at 45Hz- (whatever) +/- 3dB. According to the logic above I should set the crossover at 55Hz or higher.

Good Luck.

Charlie