For example Directiva R1 has smoother directivity because tweeter's WG is significantly smaller than woofer cone. Smaller or shallower WG is usually better for matching and smoothing directivity with phase matching XO such as acoustical L-R. Of course more balanced DI alone does not guarantee better sound.
Here is DI curves of some cheap in-wall designs and smaller Kef coaxials visualising the difference to KH150; how much and smoothly DI could/should increase to get more balanced and open sound to off-axis and random listening positions.
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