Why I Don’t Actively Mix Monitors From Control Groups
Input Channels, Auxes, Groups, Matrix Outs, and Control Groups (CG): these are the five primary channel types on DiGiCo consoles. The typical FOH audio console routing structure would include inputs being routed into a few groups and those groups sending to a master group. That master group would then be fed into a matrix with the outputs being left, right, sub, and front fill. Auxes are used as FX sends or talkback buses, but not much more.
Control Groups are usually where the magic happens. It allows you to “remotely control” any other channel type. You could group all of your drums inputs together and have control of all channel fader levels with a single finger. Say you want to keep the relative volume and compression of the drums into your drum group; you could use a Control Group to control your drum group(s) instead of the drum input channels. Regardless of your approach, Control Groups allow you to streamline mixer control and maintain fader gain structure from song to song without compromising fader resolution.
It sounds like Control Groups are awesome for FOH mixing. I am sure they would also be equally useful in any monitors, right?
Arguably, Control Groups are even MORE useful at monitors. If FOH follows the signal flow of input channel > group > matrix > PA, monitors are generally input channel > aux > wedge/sidefill/IEM. Because a Control Group can typically only control inputs, auxes, groups, or matrix outs, the send feed from an input to an aux can only be controlled if the aux send is post-fader. Pre-fader and post-fader are terms that refer to the pickoff point for the aux send; whether the channel fader affects the send value (post-fader) or not (pre-fader). The send itself allows a single input channel to drive any number of mixes, limited only by the console resources. This is one of the significant differences between a FOH showfile and a monitor showfile. Monitor engineers typically live in a mode on the console called “sends-on-fader”. This is when the faders for each channel become controllers for the sends based on the aux (or mix) selected.
Regarding pickoff points: when building a dedicated monitor file, mixers can decide whether they want to use pre-fader, post-fader, or even pre-mute for their aux sends. These pick off points allow for a number of flexible routing and control options. Some engineers like to disregard the input fader completely and set everything to pre-fader, while some like to set all input faders to unity and utilize the faders to mix moments throughout the set.
While the FOH mixer is only concerned with a single mix for the audience, the monitor engineer is juggling multiple mixes simultaneously. For the artist, I actually use the channel faders for their mix and then utilize auxes for the rest of the band. This is because I can also take advantage of more in-depth mix control using groups; much like FOH would.
Thanks for the Monitors 101, but how does this apply to Control Groups?
If a Control Group is remotely controlling an input fader, it would therefore also relatively control any aux sends that are post-fader. This would be a very similar use case to how FOH uses Control Groups in that you can control a whole drum kit with a single fader.
Here is where it gets even more useful: DiGiCo has a feature on their Control Groups labeled “Aux Sends” where when you solo an aux, the Control Group jumps to the midway point of the fader so that you can control the members of the Control Group relative to their current send value. For example, if I have a kick at -6dB, snare at -4dB, and tom at -8dB, and I raise the drum CG +2dB, the resulting change would be kick -4dB, snare -2dB, and tom -6dB. Instead of raising each aux send by 2dB, I made the same change in 1/3 of the time.
Cool, so it sounds like you do use Control Groups. I thought you said you didn’t.
I love using Control Groups in the aux send mode. However, at monitors, I do not like using Control Groups in the traditional sense. My Control Groups are set to be in aux send mode and left at unity when not in sends-on-fader mode. If something needs to be changed, I reach for the fader itself, not a Control Group.
Why?
First is speed. I have spent years mixing on only aux sends. If I am mixing the artist on a bank of Control Group faders and one of the band members asks for a change, I am forced to swap to the band member mix, as well as change the faders to the layer with the requested mix change. With the way I like to mix, the channel fader and the send fader are often the same and typically around the same general level. This makes swapping between mixes much faster in my experience.
Second, not using Control Groups helps in minimizing gain structure complexity. Control Groups in aux send mode are relative because they actually change the value of the aux send, compared to how a Control Group remotely adds or subtracts the level of other channel types.
Third, even though I could still use the Control Groups for the artist, the groups I have set up are more utility for mix building rather than actual mixing. Everything is grouped logically by player such as drums, bass, guitar, keys. However, when I am mixing, I like to grab specific inputs from each player based on the parts.
Fourth is how I handle solo parts. This solution stemmed from moments throughout the set where different vocalists are featured. For most of the set, the vocalist needs to act like a BGV in everyone’s mix; present but not overbearing. However, when they switch from harmony to lead, everyone needs to be able to hear them.
There are a few ways I have seen mixers handle this. I could snapshot those songs to have that vocalist be louder just for those moments. The problem is these vocalists don’t lead the whole song, they only lead portions and sing harmony the rest of the time.
The next option is to add a double patch, where I could have a BGV lead and a BGV harmony channel. This gets complex and adds more resources that I do not necessarily have available.
I could use groups to have a lead and BGV group. This also adds more complexity, and swapping between groups mid-song could feel disjointed if I don’t nail the timing. I would rather use a fader move than a button press.
So far, it is sounding like I should use a Control Group to handle these mix moves. Generally I would agree, however, since I am mixing the artist on the channel faders, all the BGV sends to the band members are set to pre-fader.
My solution is simple in concept, but a bit confusing to execute. I ended up using the snapshot at the top of each song to change the sends of vocal mic to the mixes that need to change mid-song to post-fade. The snapshot would then adjust the value of the send to compensate for the value that the channel fader is at on the artist mix. For example, if the BGV1 send is normally at -20dB pre-fader for the guitarist and -15dB for the artist, changing the send to post-fader adds those values together, resulting in a -35dB output of BGV1 for the guitarist mix. I have to manually adjust the value to match the original intended output.
I understand that this is confusing to grasp without a demonstration, so let’s break this down:
We will look at the background vocalist channel that sends to the artist and the guitarist to keep it simple, but keep in mind this propagates to all mixes that need this adjustment.
Song 1
BGV Vocal Channel
(Artist Mix) Channel Value = -15dB
Guitarist Send Value (Pre-Fader) = -20dB
Song 2 (BGV is featured in verse 2 and chorus 2)
BGV Vocal Channel
(Artist Mix) Channel Value = -15dB
Guitarist Send Value (**Changed to post-fader**) = -5dB
Because the guitarist send value changed to post-fader, I had to compensate for the -15dB channel value from the artist mix. The resulting send value would still be -20dB. However, now when I boost the vocalist for the artist during verse 2 and chorus 2, the guitarist will receive the same boost.
I know this is not a perfect system, as the relative change would not necessarily be a perfect volume bump for both mixes. However, in the world of live audio, everything is a compromise. I try to be focused on the artist mix as much as possible. This allows me to make those mix changes in a slightly more dynamic fashion without adding extra mid-song snapshots, immediate volume boosts, or frantically switching between mixes to adjust for feature moments.
There are so many ways to approach mixing. This is I would love to hear if you have found any unique ways of accomplishing great monitor mixes.
