Sorry for not being more specific, but I have been using the Fans tab on the Octo. I've tried the Power preset mode, and at 0% power the fans turn off, as expected, but at 1% power they turn on at ~1100 RPM. Using the target temp and curve controller modes, I have not been able to get the fans to run under about 1000-1100 RPM, either.
My motherboard was able to run them as low as about 600 RPM, and that was at roughly 30% power. They are also significantly louder with the Octo, which confirms the higher RPMs.