How to Mix Sound, Session 5: Mixer Principles

They’re all pretty much the same, underneath

Yes they are, but they all will look different. Sound mixers go by two traditional names: ‘mixer’ and ‘board’, short for ‘audio board.’ More formally, they’re known as ‘consoles.’ (Or sometimes like when you’re trying to impress the client.) You’ll hear all these terms used interchangeably.

There used to be a great diversity in the way mixers were built, but the transitory nature of the music business has caused manufacturers to design their boards to act in a similar way. About the only way that manufacturers can get any differentiation is by offering different looks and feature sets. Lately, boards have gone to digital amplifiers and have added digital interfaces, where the physical faders are just mechanical units to translate your changes into virtual interpretations within the board processor.

But they still all work pretty much the same. Whenever you step in front of a new or different board, the signals all flow pretty much the same way. And that’s what you need to remember. It’s all the same, no matter how many inputs, groups, sends, and outputs the mixer has. Don’t get lost in all the pretty colors or cool LEDs, or that nifty touch-screen LCD they planted right in the middle of the board. If you can remember basic signal flow, you can master any situation in which you find yourself.

There are differences in small mixers versus the larger consoles. Small mixers are purpose-built and can be things like electronic field production (EFP) mixers, where compact size, battery power, clean audio, and basic functionality are most important. For those types of mixers, the important thing is getting the sound to the recorder cleanly, and you’ll process it as necessary later.

We’re dealing here with console-type mixers, so that’s going to be the purpose of the rest of this material.

Take a break and hit the Net

Go to Allen and Heath and pull down a PDF of one of their current mixers. I’ll use them as the basis for all the terminology, as they use industry-standard signal flows and function names.

First, we’ll look at the functions of each of the mixer’s controls, then we’ll build an understanding of how they work together.

 Button-by-button first: What things do

The red button on the top turns on the phantom power, for condenser-type microphones which require power to work. (Off for dynamic mikes.)

Second button down is an attenuator. If you’re bringing in a line level, push this button to knock the signal level down for line-level in.

Third button down with the circle symbol is phase reversal.

The Gain Set knob sets the gain for that channel.

Next button down is a high-pass filter. It knocks off the low frequencies, beginning at 100 Hz. Why do you use this when you already have a graphic EQ section down below? It’s because the graphic EQ has distortion associated with it, and this is a low-distortion filter. Remember, always try for the cleanest sound.

Next comes the EQ section. It’s separated into a single knob for high frequencies, a single knob for the lowest frequencies, and two knobs for upper middles and lower middles. The reason for two knobs in the mid frequencies is that it allows for fine-tuning of your equalization. Sometimes you need to just pull out one small area in the sound stage, or boost it a bit. There’s a button to cut the whole EQ section in and out, so you can hear the difference while you’re setting up.

Next come the SENDs. You can make the SEND outputs independent of the fader setting by pushing setting the switch to POST (output depends on fader) or PRE (output independent of fader).

PAN sets the ratio of sound to either the left or right channels.

MUTE kills the output of the channel.

The PRE button sends pre-fader level to the headphone jack.

The level meter shows the sound levels within this single channel.

The Group switches next to the fader set the routing for this channel.

Next session, we’ll go through how each control works when in operation.



(Same as last session. Read on.)

Find yourself a copy of some ‘classic’ music and listen to how the sound crew put together the three-dimensional stage of sound. Find something that matches your tastes and give it a good, deep listen with your eyes closed. Some examples would be:

  • Classical and symphonic music from most any era
  • Jazz music from any era up to the 80’s
  • Rock/Pop from any era up to the 80’s
  • Vocals from any era up to the 80’s

So now do something different: find a well-produced piece from, oh, let’s say the Disco era. (Yes, go ahead and laugh.) But – listen closely to any Bee Gees album and you find several things: Heavy rhythm, heavy bass, clean sounding drum kit, lots of guitar and keyboard in the mix, super-clean vocals. Every voice and instrument is distinct.

But notice something: It’s INTELLIGIBLE!

Now pick up most any later-produced “rock” or “grunge” piece and try to sort out the vocals. Try to sort out the individual instruments.

Harder than you thought? You’re hearing the result of an indifferent mix, the lack of any art in sound mixing. The result of “well we just recorded it, make us an air cut with the remainder of the 2 hours we paid you for”. Now go back to the Bee Gees and listen again. You can hear the space. Compare with the “grunge” again. Sound like it was recorded in a parking garage?

Now you’re getting it.


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