I haven't used the Rythmiks in this fashion for several years, and I'm away from home for a couple weeks to check, but my recollection is they have the option to connect to the amp taps and have a knob to adjust the xo frequency so your loudspeakers run the full bandwidth and Rythmiks run from the bottom up to the set xo frequency. Another phase knob and PEQ adjustments.
Alternatively there is the option for the internal xo fixed at 80Hz. And lastly the option for line input, which is what I use in my active system but xo and phase correction are done upstream and not really what OP was asking about.