Use Reverb With Mic Cues

This How-To is quite wordy, because this concept is a little complicated. However, by going step by step, the complexity should unravel somewhat.

The trouble with reverb on Mic cues, in general, is that most reverb plug-ins only work with a specific number of inputs (generally one or two), and that is seldom the number of input channels available in a Mic cue.

The reason for this is that the number of inputs on a Mic cue is equal to the number of input channels on the audio device you’re using. If your audio device has, say, four microphone inputs and four line level inputs, then each Mic cue will have eight possible inputs, and thus eight rows in the matrix mixer.

So, to use reverb on a Mic cue when using that device, you either need a reverb plug-in that supports eight channels of input, or you’ll need to put the reverb on an output or a pair of outputs. You can put AudioUnits on either cue outputs or device outputs; we recommend cue outputs in this case, and you’ll see why later on.

For this How-To, let’s suppose you’re using an audio interface with a microphone plugged into input #1. Let’s also suppose that you’re using only two speakers, plugged into the interface’s output #1 (left speaker) and output #2 (right speaker.)

We’re going to use Apple’s AUMatrixReverb which requires two channels of input.

1. In QLab, open Settings and choose Mic from the list on the left.
2. Click the Edit Patch button next to the Mic Patch that you’re using. This opens the Patch Editor for that Mic Patch.
3. In the Device Routing tab, note that cue outputs 1 and 2 are routed to device outputs 1 and 2.
4. Route cue output 3 to device output 1 and cue output 4 to device output 2. The initial result of this means that sending audio to cue output 1 or 3 will send that audio to the left speaker, and sending audio to cue output 2 or 4 will send that audio to the right speaker. Remove any other routing.
5. In the Cue Outputs tab, in the row for cue output 3, click on the drop-down menu that says 1 channel and change it o 2 channels. This links cue outputs 3 and 4 together as a stereo pair, which will accommodate AUMatrixReverb’s requirement.
6. Still in the row for cue output 3, click on the drop-down menu that says Add effect… and select Apple > AUMatrixReverb.
7. Click the Edit button for the effect, and adjust the effect to taste. Important: keep the mix parameter at 100%, which is to say all reverb, no dry signal.
8. Close the effect editor, and click Done in the bottom right corner of the Patch Editor.
9. Click Done in the Settings view of the workspace to flip it back around and see your cue list.
10. In the cue list, create a new Mic cue.
11. With that cue selected, look at the Device & Levels tab of the inspector. You should see that the slider handles for cue outputs 1 - 4 are all colored yellow, meaning that they’re all routed to device outputs.
12. Now, when you route audio from input 1 (row 1 in the matrix mixer) to outputs 1 and 2, you’ll get dry signal from your microphone. When you route to outputs 3 and 4, you’ll get reverberant output. You can therefore think of outputs 3 and 4 as an effects bus, or auxiliary send, and vary the amount of reverb by varying the mixture between outputs 1 and 2, and outputs 3 and 4. This is why, way back at the beginning of this How-To, we suggested using reverb on cue outputs, rather than device outputs.
13. Finito!