Dana, "filter out unwanted hum" means that that may be the only thing found above about 80Hz in the LFE channel. The LFE channel extends to 120Hz, but in practice, little or nothing above about 80Hz is mixed into it.
Yes John, I was just reading quite the debate over 80hz vs 120 at avs. Some say 120hz as this setting lets you hear what the sound engineers intended you to hear. Then Chris from Audyssey states he thinks it's a mistake that mfg's even include this as an option at all, because it just confuses people. haha I was one of them!
Then again, if it can filter out unwanted hum, then that's a good thing. Either way, it will be fun to experiment with.
Dana
