@avsjerry
On the contrary. I think dipoles ruin soundstage and imaging by scattering sound willy-nilly about the room. Mine are blocked off at the backs and the "block-off" is a piece of modeling foam of a very specific size and shape covered with felt that is pushed into the V-notch.
The rear reflection repassed through the front opening interacts with the diaphragm and creates a quasi ~3rd-4th order crossover at ~3,500Hz (regardless of your crossover setting) and instead of the Heil getting louder with frequency, this flattens everything above 3,500 Hz WHERE THE DETAIL LIES to ~12,500 Hz.
Acoustic foam behind that ensures that any stray rear sound is further reduced.
All that stuff on the front is nice. It improves soundstage, imaging, and focus by reducing ceiling/floor bounce, but the magic is in the rear.
https://audiokarma.org/forums/index.php?threads/im-fixing-a-hole-heil.1025205/
Great Heil response curve crossed over at 3kHz.
Modified Heil response curve. It is actually flatter/smoother now with the felts added. Do you see where the detail lies?