I think it's about the same as free-air resonance - backwave to entire basement. Precedent: pre-war theatre horns
(open rear like Shearer/ERPI)(unlike post-war reflex tuned designs like Altec A4)(I don't like reflex boxes - did not like
416 in Altec 620 box)
that live with resonant amplitude rise. Cone control seems reasonable within moderate power limits. Modern movie/TV
mixing has some massive deep low bass which could damage some drivers without subsonic hi-pass filter.