@fastfreight
I use a Danville Signal dspNexus, which processes 8 channels at up to 48/192. It comes with software that lets you design the system using whatever crossover slopes you want.
I run my Magnepan 20.1s full range and use four large subwoofers to support the bottom end. I measure each speaker and the listening position with Room EQ Wizard, then feed those measurements into Multi-Sub Optimizer. From there, I build 8 biquad filters on each channel, which gives me a huge amount of control over response, phase, timing, and room modes. These are IIR filters, the dspNexus also can process FIR filters.
The payoff is big. Imaging is excellent, and the bass is tight, controlled, and very deep without sounding bloated or boomy. Since the dspNexus works as an active crossover, it goes straight into the amps, which then go straight into the speakers, so there are no passive crossovers in the signal path soaking up power. Each driver gets exactly what it should.
The amount of control you get with phase, amplitude, time delay, room correction, and master-clock timing is just on another level. There’s no way I could get this kind of performance trying to do it manually.

