The bass management section (p.18):
The XMC-2 has three outputs designated for connecting subwoofers. These can be configured in a number of ways, depending on the number of subwoofers you have, the number of height speakers you have, and your bass management preferences.
The Center Sub output may be configured as either LFE, Mono, or None. The Left/Right Subs may be configured as either Mono, Dual Mono, Height Speakers, or None.
If the Center Sub is configured as LFE, then all Low Frequency Effects (LFE) content from surround sound sources will be routed directly to the Center Sub, LFE content will NOT be routed to the other subs, and no content will be routed to the Center Sub by the bass management system.
The Dolby Atmos consumer standard only specifies a single subwoofer channel. This channel contains the sum of any content that originates in the Low Frequency Effects (LFE) channel of surround sound material, and any low frequency content that is routed to the subs by the bass management system. This channel is then distributed to however many subwoofers you have configured. (Each subwoofer may be calibrated and adjusted separately, but they all receive the same content, in what would be considered “mono”, “dual mono”, or “triple mono”.)
However, because some users prefer to use different subwoofers for music and for movies, we have included an extra option that provides significantly more flexibility.
If you connect any combination of one, two, or three subwoofers to the appropriate outputs, and configure those outputs as Mono or Dual Mono, all of your subs will be treated equally, and will be used for both LFE content and content directed to your sub by the bass management system.
However, by connecting one subwoofer to the Center Sub output, and then configuring that output as LFE, you may instruct the XMC-2 to use that subwoofer exclusively for LFE content. That sub, in effect, becomes your “low frequency effects speaker” for movies. All LFE content is routed only to that sub, and any low frequency content that is redirected from any other channels by the bass management system is routed to your OTHER sub or subs.
Note: If you plan to connect two subs to the Left Sub and Right Sub outputs, then you must configure the Left/Right Subs outputs as Dual Mono. If you plan to connect only a single sub to those outputs, then you MUST connect it to the Left Sub output, and you must configure the Left/Right Subs as Mono. When Left/Right Subs is set to Mono ONLY the Left Sub output is active. (This setting is independent from the configuration of the Center Sub output.)