Did you look at simple hardware monitor selector boxes ?

https://www.thomann.de/de/palmer_monicon_xl.htm

https://www.thomann.de/de/spl_mtc_mk2.htm

Hi tobywburroughs.

Welcome to the RME user forum!

I’ve put some thought into this and have a proposal that could save you the cost of an additional monitor controller and even provide extra flexibility. Think of it as a potential "workaround" that offers some added features.

It may not be exactly what you're initially were looking for, but I think it's worth considering.

Proposed solution or "possible workaround"

a) Continue using "Main Out" and "Speaker B" for the two pairs of speakers you use most frequently.

b) Use mute/unmute in HW outputs to activate monitoring for any additional monitor pair (besides Main Out/Main Out B)

This functionality can be further enhanced by using any of the two features below in addition:

c) Mirror the submix of "Main Out" for any additional monitor pairs. This way, all other pairs will receive the same submix as "Main Out."

d) Use fader groups to synchronize the volume across all active monitors with "Main Out." With the ARC USB, you’ll be able to control the volume of "Main Out" and any other submixes with monitors.

Results:
- You can still switch between Speakers A and B.
- Mute/Unmute can activate additional monitors, with all speakers playing the same submix at the same volume level.

Further Advantages:
- This setup can scale to support more than four pairs of speakers if you need that in the future.

Benefits:
- Scalable to any number of monitor pairs
- No impact on musicians' submixes
- No additional costs for a monitor controller
- You can start implementing this setup right away
- Independent of RME’s future support for more than four speaker pairs (a feature that may or may not be added).

I hope this helps! Please let me know what you think.

Isn’t it AFL? You hear the level after the faders…

Create a fader group for all hardware outputs connected to your monitors, and include the Main Out in this group as well.

When you control the Main Out with the ARC USB, all other hardware outputs in the group will follow the volume adjustments, with changes applied relative to their initial levels when added to the group.

I recommend measuring and matching the volume level of each output before grouping them, so they start at the same level if desired. However, you’re free to set any level for each output before adding them to the group. Adjustments will be applied as a delta to each initial level—if you add +10 dB to Main Out via the ARC USB, all faders in the group will increase by +10 dB from their current values.

If you need a different volume on a particular output, you can temporarily remove it from the fader group, adjust as needed, and then add it back.

After trying a few things, I’m stumped. It won’t even let me add control room outputs to a fader group, only other channels - so seems like that solution won’t work.

I was being a bit silly thinking solos could be useful, as a bit more thought makes me realise that couldn’t be a solution.

Maybe I’ll have to wait for an update or get an analog switcher, but I love the tidyness of 1 usb cable to the remote and don’t really want to go the analog way. I can’t think of any other way to achieve this with the current limitations, although maybe I’m doing something wrong.