Hi. I got different oppinion bout the XO.For sure it has influence on the lobing. Definately, depending on which filter type u use, it will create different on- and off axis response.
E.g. i like cutting the supertweeter at 8k with butterworth even order. will give you a +3db peak on axis, but a linear average (all axes) response.This is nice as the 8k peak gives a touch xtra resolution and stage size. The overall balance is still fine.
The next favorite XO between mid & hi is 3 or 3.5k. Ears most sensitive in that region. Many people, listening to very loud female voice especially, like to dipthe response in that region (bbc dip). Thats according to Linkwitz the region where our ears got different response depending on the listening angle.So what i do, i cross at 3.5k with an linkwitz (or any other flat summing -6dB XO point) filter, that gives me linear on axis response, but an overall energy dip of -3dB xactly there. Which fades the indirect sound a tiny bit to smoothen "the shout".
Another region of sensitivity is 200Hz. Below youre very sensitive to phase shifts, above less.
Also one should try not to have alisson effects of surrounding walls near the XO points. Generally. This is the worst of all.
Last but not least, try to measure more. Not just RTA. But hi-res sinus sweep. Try outdoor measure. Gives you real hi-res curves and unvieles weak spots of the driver. Especially distortion. Try not to reach amplitude ripples on the top. Most of all, try to cross to highpass before the D3 odd harmonic raises. The measures will narrow your best options down more than you want 
cheersjosh
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