@millercarbon, one thing to be aware of is that there may be more to the difference between a given company’s sealed and ported subs than the sealed or ported enclosure itself. Rythmik Audio offers subs with either a 15" or 18" woofer in both a sealed and ported enclosure, and using the provided foam plugs to block the ports in the ported model does NOT, according to Rythmik design engineer/owner Brian Ding, make them identical (for reasons explained by Ding in the technical pages of the company’s website). Interestingly, his subs using 8" or 12" woofers are offered as sealed designs only, not ported.
Highly technical details on all aspects of sub design are provided on the Rythmik Audio website. Well worth reading, even if you elect to get a sub or four from a different company. Speaking of four subs (a real good idea), as Duke said a swarm can be created from any group of subs, four identical ones perhaps easiest to optimize in a room (for reasons, again, explained by Ding). Another subject covered by Ding is that of mixing sealed and ported subs in a room. Though he recommends not doing it (again explaining why), for anyone insisting on doing so he provides the information necessary to do it correctly. The plate amps on the Rythmik subs include controls to aid in that endeavor, including continuously-variable phase and 3-position damping.
