The Black Box is a Low Frequency Resonator Array that works in conjunction with the Subwoofers, Atmospheres and FEQ X4 to solve bass node issues.
sbayne, having the Rythmik F8's is very cool, as is using them as bases for the Tektons. May I make a suggestion? Go onto You Tube and watch all the Tech Talk Tuesday videos that Danny Richie of GR Research (Rythmik Brian Ding's collaborator) has made. Find the episodes in which Danny discusses the problems caused by employing multiple tweeters on the same baffle. With two Tekton's stacked, you are creating some serious phasing, lobing, and comb filtering issues. The huge distances between the various tweeters is unquestionably creating some out-of phase cancellation at certain frequencies.
But, if you like the resulting sound, that's in the end all that matters.