Locate the level meter on your crossover unit. These lights will tell your monitor whether or not your gain is clipping during adjustment.
Turn the gain knob up until the level meter reaches green or yellow. A red light will indicate if the gain is clipping. Turn the gain down slightly until the red light disappears.
Turn the crossover knob to select where you would like to set the crossover point. In a standard two-way PA system, a normal crossover point is between 80 Hz and 100 Hz. These frequencies are good for subwoofers, while everything above them will go to the top boxes of the PA system.