Tom, that receiver manual provides essentially no information about bass management, and it shouldn't be assumed that if the speakers are set large and the sub on that the sub would be doing anything most of the time. Typically it would get nothing with those settings except at the times when there are low frequency effects(LFE)present during movies. So, that might not be a good idea, but if Sony won't reveal this secret information, experiment to see when the sub actually operates.

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Enjoy the music, not the equipment.