Kev and I have just been doing a sanity check, testing the presence of the sub when mixing. When monitoring stereo via the rec or mix buss, or surround via EXTA, we can confrm that turning on bass management splits the signal at 80Hz and feeds the satellites with everything above, and the sub with everything below. When bass management is off, the full frequency range goes to the satellites and nothing goes to the sub, in both stereo and surround modes.

So, the only way to have the sub in your monitoring is to turn on bass management by selecting the MONITOR OPTIONS button followed by BASS then BMN.