Yea. I found on Yamaha's website, that if all speakers are set Small, and bass out to sub, that all LFE/BASS for those channels in directed to the sub.  Now if all speakers are set small and LFE/BASS out is set to BOTH, then all again is directed to sub.   This is right off the site.   I agree the manual was not clear.   The reason this is come up,  is when ( both ) is selected, and mains  are set  a (small ) the Subs  come to life.    I have a feeling That when  set to small,  the bass management is not redirecting main channel bass to sub. Unless mains  Channel is set small,  and bass out is set  to both .    again  according to their website, if    Bass out is set  to both,   And mains  are set to (small )  LFE/bass  is directed to the sub.    Thanks for responding PENG