That makes perfect sense.

I would think the formula Linkwitz gives to approximate the angle where crossover nulls occur is pretty vague, as you could quite easily have a path length distance where the sound sources are exactly or are near 180deg apart even when the system axis is not tilted, or only tilted slightly. Especially since it doesn't consider crossover slopes, then that formula is a little too much of an approximation in my opinion!

Thanks!
Adrian