Last night I did some testing with my Radio Shack SPL meter and Test CD 3 from Stereophile. Track 17 of this test CD has test tones that step in third octave increments from 200Hz down to 20. For all my tests I disconnected my sub and front speakers are set to large.
With all my tests I conformed what TommyBoy found when the Sub was set to None. I also confirmed what Paratrooper found when the sub was set for LFE only. I also tested with sub set to L/R+Sub. When the sub was set for LFE only or L/R+Sub there was no difference between Bypass and Upsample no matter what I set the X-Over to. Something else I found was that when sub was set for LFE or L/R+Sub the volume level between Bypass and Upsample was identical.
From what I found the sub should not be set to None even if you don’t have a sub. I know it shouldn’t be this way and hopefully the software update will change that along with some other things.
On a related subject, below is a link to an article on Polk Audio’s Web site on how to connect a subwoofer. They agree that bass management is a confusing topic and they have some suggestions that you may find useful.
http://www.polkaudio.com/education/article.php?id=19
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