At the risk of over-simplifying, imo a speaker should get two things right: The direct sound, and the reflections.
The direct sound is the most important, but imo the reflection field matters enough that it’s worth getting right (unless the system is set up for near-field listening).
What constitutes "reflections done right" is an area where there are differences of opinion. Imo the reflection field should be spectrally very similar to the direct sound; it should be neither too strong nor too weak; it should begin arriving neither too soon nor too late (the latter is virtually never an issue in a home audio setting); and the arrival directions matter, particularly for the first reflections.
(In addition, the reflection field should decay evenly across the spectrum, and should decay neither too fast nor too slow, but this is a room acoustics issue over which the loudspeaker itself has little influence.)
My preference is generally for controlled-pattern multi-directional speakers, assuming they can be set up correctly in the room. Dipoles and bipoles, for instance, need to be far enough out into the room.
I have been commercially involved with fullrange dipoles, fullrange bipoles, dipole/cardioid hybrids, and speakers with rear-firing drivers which are not full-range bipoles. Imo each of these formats have worthwhile advantages, but there are always tradeoffs.
Most recently I have been involved with speakers which have relatively narrow frontal radiation patterns plus highly adjustable rear-firing drivers. The general idea is to manipulate the reflection field independent of the direct sound, with the intention of making the reflection field more correct that it could have been with front-firing drivers only.
When both the direct sound and the reflection field are "done right" (and obviously the room gets a vote in the latter), instrumental timbre is natural-sounding; listening fatigue is minimized or eliminated; and we are more likely to get a "you are there" spatial presentation, wherein the acoustic space on the recording is perceptually dominant over the playback room’s "small room signature".
In my opinion.
Duke
dealer/manufacturer