I am not familiar with the Klipschs so my comments are based on the PC13Us.
James did not measure those but even the PC2000 that are a couple notches below has the following:
That's without room gain!
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The PB13U was measured, it should behave about the same as the PC13U in terms of measurements:
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Regardless of the mode, those big SVS just don't drop so rapidly from 22 Hz down, even in quasi-anechoic, let alone in room, and with Audyssey XT32 SubEQ HT incharge.
Here's my own, 9 positions, Audyssey OFF, for the front left+right+sub1 and sub2 (SVS subs), no such big loss below 20 Hz, we both know it is room dependent, but the OP has a large room so it should only be smoother, probably with less peaky room gain than my smaller room, but should have no major dips either.
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