7x9? With 8ft ceilings, that would make for a 500 cubic foot room-- smallish and easy to pressurize. anyway, here's another review, and it comes with graphs. This one notes that the surrounds aren't true dipoles-- though it still meets Select standards.
No need to be sarcastic, Arthur. But do note that the M&K S150 speakers are also of a "different design". than the Atlantic speakers. And so are the M&K LCR-750.
A note of caution:
source As for THX philosophy-- as long as it passes the certification, the means of doing so is irrelevant. Now, there may be definite advantages to the Atlantic system, but for whatever reason, these were not incorporated into the spec. THX Select subwoofers are flat...