Why do you need to switch via Snapshots instead of Workspace when you are switching 'projects' anyway? I mean that's not a simple different music file, it's a big change in the DAW as well. And are you aware of the Workspace Quick select hotkey W?

@MC In my opinion the most important part of that message is this:

It is very common to mix without a subwoofer and only turn on the subwoofer occasionally for checking the mix. A lot of people work this way to reduce listening fatigue. When the sub is off, the crossover needs to be disabled so the monitors are doing all the work; when the sub is on, the crossover is enabled. It would be very convenient to be able to do this using snapshots, especially for users of ARC USB. I don't have ARC USB but use MIDI to switch snapshots which is basically the same idea.

From the name "Room EQ" I'm guessing RME didn't intend this to be used as a crossover, but in practice people are going to want to use it as a crossover because it is perfect for that. Maybe RME thought people who have a subwoofer would always use the subwoofer enabled but, like I said, that's not always true. In fact, more complex situations are possible: different subwoofers, bass shakers, etc, each requiring a different crossover and the ability to be selectively turned on and off. The ability to toggle all this quickly with one click or the press of a button is a big workflow boost.

That is correct but there are a couple of caveats, firstly workspaces can't be switched unless Totalmix FX is the active window, so you can't just press a button to switch; and second, loading a workspace almost always shows the "Discard all changes? Yes/No" confirmation dialog, which places a small cognitive load on users (by requiring users to understand the prompt and click the correct button), and requires mouse motion and one click. Using ARC USB and snapshots it's just one button press, boom, done. Last, if workspaces can do everything shanpshots do, and snapshots can only do a subset, then I might as well just use workspaces and forget snapshots, but that renders my dedicated hardware controller useless.

If that had worked I wouldn't be here! Proper sub integration requires the LF signal to be time-aligned, so we need to use the delay function in Room EQ. Actually, I have Genelec monitors so the GLM software takes care of that, but I also use bass transducers (aka bass shakers) which are "slow" compared to the monitors, in other words, I hear the monitors first and about ~10 ms later feel the vibration from the bass shakers. If I'm using headphones, the latency becomes ~20 ms because of the headphones signal shorter "time of flight". In an ideal world I'd just make the shakers "faster", but the problem is the working principle of a shaker involves a relatively large moving mass that needs to accelerate and decelerate and that, because of the nature of physics, takes time, in this case about 20 ms. Since I can't change physics and I can't make the shakers faster, the solution is to slow down everything else, so I delay the monitors and the headphones.

The trade-off is increased latency. Luckily, a few extra ms of latency isn't really a problem for mixing, mastering, watching movies, gaming, etc. However, it is a problem when tracking vocals or playing soft-synths. In other words, there are situations where it's ok to have a bit extra latency and situations where it's not. Therefore, if I'm tracking I will mute the bass shakers and disable the delay function inside Room EQ for both the monitors and the headphones, and if I'm doing any sort of latency-insensitive activity (mixing, watching a movie, etc) I will un-mute the bass shakers and turn on the Room EQ delay.

At the moment I use Totalmix FX's audio loopback function to route audio into an instance of Reaper with EQ and delay plugins (I actually use Ableton Live, and here Reaper is merely a plugin host for the EQ and delay plugins). Reaper then outputs separate signals with the correct delay amount for the monitors and headphonesand a bit of EQ for the shakers. To tie everything together I have two snapshots in Totalmix FX, one that un-mute the bass shakers and routes audio into Reaper, and another that mutes the bass shakers and routes audio directly to my monitors and headphones. It's a bit convoluted but this approach allows me to toggle between bass shakers/no bass shakers simply by recalling the appropriate snapshot. In fact, I have more snapshots than that:

Headphones without shakers
Headphones with shakers
Monitors without shakers
Monitors with shakers

Room EQ allows me to do all this entirely in TotalMix FX, without the need to use Reaper and plugins. The problem is, if I can't use snapshots it's just not convenient. With reaper at least I can map my MIDI controller to mute/unmute tracks so I get the desired routing. In the end the whole thing happen with one button press. It's pretty sweet actually, but the whole things feels a bit "fragile" or "hacky". It would be rather lovely to have it nice and solid in Totalmix FX.