I have an Onkyo 876 with a 5.1 system. I used Audyssey and used all 8 measuring points around my couch. I'm using 340 classic as the LCR. I 'm using the HTM-200 as surrounds, mounted 6 feet high, about 3 feet above and 9 feet to the side of the listening position. They are mounted upside down (vertical orientation), but I don't see how that's an issue.

When Audyssey went through the "chirps" at the first sampling position to the side of the primary listening area, it increased the volume of the chirps on the HTM-200 twice. And at each subsequent sampling position the HTM-200 chirps were SIGNIFICANTLY louder than the LCR chirps.

At the conclusion, Audyssey says the HTM-200 should be crossed at 90 Hz. But they should be good down to at least 80, the spec sheet shows 74Hz.

Is this due to the off-axis falloff?

I've decided to use 80Hz anyway.