I have good Mackie HR824 monitors, but have added a smaller sub with excellent definition to the mix. How can I take my usual LogicPro stereo output and put the sub in place. This sub does not have line in and out to crossover into the Mackies. Rather, I need to send the original mix to the sub and the Mackies and engage its continuous crossover from 50 - 180 Hz. O I send the whole signal to the Mackies and the whole signal to the sub. Or do I roll of the signal to the sub around the crossover point and adjust to taste? I assume I need to roll off and adjust the signal to the Mackies. Can I make a mult of the output channels to the sub?