How to Use Matrix Mixing

The Matrix is a sub-section of medium- to large-format live sound mixers. It’s designed to simplify the mixing process by providing a more logical, and more practical, signal flow; and it’s particularly applicable to solving a variety of problems you’ll encounter in worship sound. If you’re not taking full advantage of the Matrix, you’re making life more difficult for yourself—so let’s find out what the Matrix is all about.

The simplest way to describe a Matrix would be a “mix of mixes,” or as a mixer within a mixer (stand-alone Matrix mixers are also available). This can be done in hardware, or virtually, in software. The Matrix mixer’s main job is to make it easy to route multiple inputs to multiple outputs. The Matrix’s columns are inputs (that come from outputs), and the rows are outputs (that go to inputs). Placing a potentiometer at each junction of an input and output lets you send any amount of any input signal to any output destination (Fig. 1).

Fig 1 Mixer Matrix
Figure 1: The knob arrangement makes it clear why this section of a mixer is called a “matrix.”

The number of controls in a Matrix mixer consists of at least the number of inputs multiplied by the number of outputs, although there may also be additions like assignment switches or mute buttons.

Why You Need a Matrix Mixer

When you build your house mix, you’re combining various elements—microphones, instruments, sources from DVD, CD, computers, etc. You then route these to the main outputs, which feed the speakers in the sanctuary.

But that’s not the only mix that matters, because the musicians need to hear themselves. The musician/vocalists receive a mix of the different elements that they need to perform from the Auxiliary/Monitor outputs. This mix comprises the same microphones, instruments and in some cases backing and click tracks (and maybe some crowd microphones, if the band is using in-ear monitors). Creating this mix is like creating one for the house, but mixes for specific musicians or groups of musicians will usually be independent of, and different from, the mix the congregation hears. For example, the bass player may want to hear more drums than any other musician to make it easier to “lock in” to the groove. As we’ll see, this is an ideal application for the Matrix mixer.

A Matrix mixer that can create auxiliary mixes is also useful for recording the service. Like mixes for the musicians, you create a mix from scratch, with levels that are independent of the house mix, that feed a recording device. There are many reasons why you want an independent mix for recording. For example, when mixing for the congregation, the louder on-stage instruments (like drums, guitars and bass) may not need to be reinforced because they can be heard very well without reinforcement. If you look at your mixer’s faders, you’d see that the levels for the louder instruments are not nearly at the same level as, let’s say, the vocals. If you send this house mix to the recorder, it would sound heavy on vocals, and miss much of what the guitars, bass, and drums are doing—which would give a thin overall sound. For a more natural mix, at the very least you’d want to add a pair of audience/ambience microphones that go only to the recording device (not to the main system’s speakers).

Practical Matrix Magic

Let’s start by looking at your mixing console. How many Main, Left/Right Outputs are there?  If it’s like the mixers I’ve seen, you’ll find one set of Stereo L/R outputs and a Main/Mono out as well. So what do you do if you want to send a copy of the Main Mix to other places in the church/campus like the foyer, cry room, or coffee bar?

Fig 2 Typical Signal Flow
Figure 2: A setup that sends mixes to multiple outputs.

One way to solve this is by using subgroups. (Fig. 2). You would assign all the inputs going to your main mix to the subgroups as well, and send that mix to wherever you need it to go for the appropriate sub group outputs (note that if you’re sending a stereo mix through subgroups, you will need to use two subgroups—one for each channel). However, this option has a major downside because when you change levels on the Main Mix, it will also change the subgroup mix. They’re not independent mixes, which can be limiting.

Here’s where the Matrix comes in. Let’s start with a most basic application: Recording the church service. Instead of using an Aux bus (output) and creating a mix from scratch, we can use a Matrix to create the mix easily, quickly, and efficiently.

Because a Matrix is a mix of mixes, you can start with different mixes when you access the Matrix. So let’s start by sending the main mix to the Matrix. Locate the controls at the junction of the Matrix inputs that carry the outputs from the main mix, and the Matrix outputs that go the recorder input, then turn up the controls to send signal from the main mix to the recording device.

Wow, that saved significant time compared to setting up a separate aux mix.

Now add the inputs you need (like drums) to the Matrix, and turn up the level control at the junction of that signal’s output and the output that goes to the recording device input. Adjust the levels of individual signal sources for the most realistic sound, and note that no matter what you do to the house mix, the mix to the recorder will be independently adjustable.

On the majority of mixers you may only have the option of adding other groups, not individual channels. If that’s case, add the instrument groups to the Matrix, and bump up the levels of the guitar and drum subgroups to make the mix more musical.

On older analog mixers you were able to add an extra input or two to the matrix beyond groups, or other buses. Today, most mixers limit the Matrix to Main L/R, Subgroups and Auxes. Very few allow you to add every input channel as well, but if they can, this can be a major benefit (of course, this also tends to raise the price—as with life in general, you can’t get something for nothing).

Fig 3 Matrix Mix selection
Figure 3: Buttons for selecting the Aux, Sub, and Matrix mixes are in the lower left of this PreSonus StudioLive 32 mixer

On top of the main mix, I can now add the groups, channels, or auxes to my recording (Fig. 3). In addition, there’s also full access to equalizers, dynamics processors, and delay. It’s even possible to insert additional microphones that aren’t in the main mix, like audience microphones, which would make no sense in the house mix but add a lot to a recording.

Wasn’t that easy?

Here’s another application: creating a front fill mix.

Fig 4 Front Fill Mix
Figure 4: To create a front fill mix, you set up smaller speakers on the platform’s lip that face the church’s front section.

When you’re sitting very close to the stage, you may hear a lot of the stage’s louder instruments but the vocals are not as present. In solution is often front fill speakers, which are set up on the front of the platform to face the front rows of the congregation (Fig 4). Feeding the front fill speakers is a perfect application for a Matrix mix.

As with the previous application, start by sending the main mix to the Matrix output, and raise the levels of the vocals and/or acoustic instruments that may be harder to hear from that position. Voilà, an enhanced mix for the front fills that took two seconds to create—talk about a time saver.

Also, in-ear monitor mixes often benefit from a Matrix mix instead of a traditional aux mix. Again, this can be a real time-saver. For example, suppose the drummer has a monitor mix that may be very similar to what the bass player wants. Instead of creating a monitor mix from zero, I’ll use a Matrix. You just send the drummer’s aux/monitor mix to the matrix, and then add the elements the bass player may want to hear. Easy!

Matrix mixers also solve problems. I can start with a stereo mix and send it to a mono input, or I could do the opposite by starting with a mono source and sending it to stereo inputs (Fig. 5).


Fig 5 Adapter
Figure 5: You can split a mono bus to stereo inputs with a simple mono-to-stereo Y-cord adapter

For additional information, and a practical example of how to use Matrix mixes with a modern mixer, click here for a video that shows the process of setting up a Matrix mix on the new Presonus StudioLive Series 3 Mixers.

When you begin to understand how to take advantage of Matrix mixes, you’ll find yourself using them more and more. And you’ll save an abundant amount of time—time that you can better use for another, more valuable purpose: Prayer!

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