When I play the advanced resolution "5.1" version of certain DVD-Audio discs (e.g. Beach Boys' Pet Sounds, Al Green's Greatest Hits), absolutely nothing comes out of my subwoofer. I don't have this problem with other DVD-Audio discs (e.g. Eagles' Hotel California, Elton John's Goodbye Yellow Brick Road). Furthermore, when I play the Dolby Digital 5.1 or DTS 5.1 versions of Pet Sounds or Al Green's Greatest Hits, the subwoofer kicks in as it should.
There must not be much happening in the .1 channel on those DVD-A's. Some multi channel SACD are the same. The fact that you don't have a problem with other titles means it's not your equipment. Try finding reviews on the discs in question and that may help such as:
