With just the right amount of 128 Atmos objects flying at you I estimate about: 150db from 30 to 300hz (subwoofers would be extra),I don't even know what to say. I can't even imagine what 7 1899s must feel like.
and then "quieting down" above that because of power-handling into the mids and tweeters. But still well above EAR-DEATH-SPL.
I only have 7 DIYSG 15's all around me, and during 2018 new-years my niece and her girlfriends came over and we watched IT at the loudest volume we could all withstand (well over THX, I can tell you that much...)
A lot of crying and screaming was involved but now... they all float down here!
and that wasn't even coming close to straining any of those speakers, so I couldn't imagine what 7 1899's would be a capable of at FULL OUTPUT!
Your ears would actually die, *if* you wanted them to... No Joke!