I've never seen or heard a swarm.
I keep yapping about 'stereo pairs' of subs, front facing, no ports, locate adjacent to mains: giving/preserving bass directionality, by virtue of both the fundamentals and overtones of those fundamental notes.
It finally occurred to me: those that use SWARMS must be adding them to systems that already have bass directionality, they are adding more to a system that has more bass than most of us have. i.e. my woofers, 15", 37lb monster magnets, I could add more below what they do if I wanted, SWARM might be best.
Adding a SWARM to a system that does not have decent bass directionality is what does not make sense to me.