Just to show the process a bit as I'm sorting things out here with DSP. Here are a few screencaps of what REW is showing my Left transducers to be doing. Horn Module and Woofer are separated with individual sweeps. Before I touch the EQ I'm aiming for smoothest phase response over the XOver region of 750Hz. I can tweak this by delaying the horn or the woofer in the driverack. Mic position is ear level, middle of the couch. When I get to the EQing I'll take 3 or 4 averages from within the listening window. Also with this data and the impulse response I will be able to gauge the positioning and effectiveness of some sound panels I will be installing.

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In the top capture, you can see the initial rise of the horn (steep spike) is aligned with the initial rise of the woofer. The peaks however are a little under half a millisecond apart. The lower cap shows phase relationship in a range an octave below and above the target crossover frequency.

Here are Left Woofer, Left Horn and a Full Range Sweep overlaid.
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I've moved the woofer .25ms forward in the time window to see what would happen at phase and crossover. REW will sum or subtract the traces as I make changes to simulate the effect. It correlates well with real-world results and so saves the time of running new sweeps for every new tweak. We can just test things in the box until we get a good result. Light green is a summation of the woofer and horn with the time shifted woofer and Olive colour is the subtraction of the same. The subtraction is useful, the deeper the notch the better. Here you can see the notch is down 28dB. This is the virtual equivalent of reversing polarity of one of the drivers and trying to get the best null with a tone playing at the crossover frequency.

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Here you can see the phase tracking a little better. The olive green is the inverted version. I wonder if I can do better in the upper region of the driver overlap.

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