Describe the sound of point source loudspeakers?

I'd say near perfect integration of the frequency spectrum. There is also an openness that may be due to that some of these speakers use little or no crossovers.

OP, are you thinking a concentric design? 

I look at my brothers MBL  Omni directional speakers to sound and behave as a real instrument 360 degrees These are a great reference point source IMO 
and I too may buy a pair next year.

A point is by definition a dimensionless or infinitely small location in space. Dimensionless or infinitely small objects cannot possibly produce sound. (Some will no doubt now go chasing after these speakers with zero room interactions.) I mention this only to illustrate how easy it is to go off the rails talking tech. Jargon is a creature unto its own.

I never once in my life went to hear a point source, or a dipole, or even a horn, folded or otherwise. Never went to audition isobaric, line array, or any other speaker design approach. All I ever went to audition was speakers. Then evaluate whatever I hear in light of the room, music, associated equipment, and yes maybe even speaker design. Maybe. Sometimes.

In other words I never put the cart before the horse.

Another audiophile version (of many such tales on this forum) and as current as the original: "The Emperor’s New Clothes"

Dimensionless or infinitely small objects cannot possibly produce sound. [Emphasis added]

... "infinitely small objects cannot possibly produce sound."

Lay version:  https://www.newscientist.com/article/dn4320-big-bang-sounded-like-a-deep-hum/   

https://faculty.washington.edu/jcramer/BBSound.html