Currently in Spat Revolution version 1.1, it is necessary to create a mono mix for a LFE channel using a workaround method. To get a mono LFE mix that will be summed into the n.1 channel in a surround configuration, create a secondary mix room. It should not have reverb, and is a special channel based configuration called 1.1 - a Mono speaker plus LFE room.
As we are not going to have an actual satellite speaker in this room, we need to set the unwanted virtual mono speaker gain to -144.5 (silent) inside the 1.1 LFE room. Sum the room output in a Master module with a transcoded n.1 Channel Based stream from the HOA room. The LFE channel from the LFE room will be summed as the .1 LFE Channel of a surround format at the output module. The overall LFE output level can be controlled using the Room Gain of the Mono room and each individual Source can send to it with a separate level ( which could be automated from the DAW of course).
How to Sum the .1 LFE
Use the Parameter Filter to create mixer of LFE sends for each source
Here is another ‘rough and ready’ suggestion that will yield a separate output route for the bass content.
Reduce the output of the HOA room down to MONO using a master transcoder module and send that to the sub speaker. The sub-bass signal will have its own gain control in the Master module. Transcode to any Channel Based format and automatically get a mono mix down of the HOA Room activity for all setups.