Output bus for subwoofer

The capability to filter dedicated outputs or a mono output with crossover filter for subwoofer(s) has often been asked for the X-Air series.
The matrices suggested in another post can be a solution, but if that is not possible maybe there is a simpler way to implement it without adding much processing power requirements, just some routing and parameter linking.

• add a special mode for a couple of Busses, to allow routing audio from Main L or Main R or a mono sum of both, eg. pre-eq, to Aux output(s)

• in that mode, synchronize the cutoff frequency of one EQ band of the Bus (set as low-pass) with one EQ band of the Main mix (set as high-pass). The Main outputs can feed the tops and the special Bus(es) through Aux output(s) can feed a mono sub (or a stereo pair) without frequency overlap.

• also synchronize the sub volume with the main mix fader, allowing relative adjustment of the sub volume and single fader adjustment of the overall volume. If needed, dedicating a DCA resource for that would be OK.

• a proper Linkwitz-Riley crossover would be ideal, but i guess this functionality would still be useful with existing filter shapes, possibly with a slight offset of the cutoff frequencies for a somewhat flat overall response. The sub Busses would not need as much EQ bands, so maybe some processing power could be reassigned to something else, eg. mono summing or better crossover filters ?

• the upcoming delay on outputs will allow for time-alignments of subs. When using two mono-summed Busses for two or more subs, the delay on one of those can also be used for a cardioid sub setup. That would be a killer feature.