The "bass management" option on today's home theater receivers is designed to route mid- or low-bass or both frequencies to a sub-woofer in the system. What setting you should select is based on the bass capabilities of the speakers in question. In general, "satellite" and bookshelf speakers should be set to "small."
Floor-standing speakers should be set to "medium" or "large" depending on their ability to accurately reproduce deeper bass. At the same time this option is set, the frequency of the sub-woofer's bass reproduction should also be set. If, for example, you have small bookshelf speakers you have set to "small", you should set your sub-woofer to 100-120 Hz.
If you have big speakers set to the "large" setting, you should set the sub-woofer lower (i.e. 50-80 Hz). The correct settings on both the receiver and sub-woofer will allow the sub-woofer to pick up the bass where the speaker leaves off; creating a smooth transition that reduces "boominess" at frequencies both the sub-woofer and the speaker are delivering. The correct settings are best obtained after experimentation yields the best sound to your ears.