Are you excited to start mixing your very first live show? Or simply want to set up a rehearsal studio for your band? Then you need to learn more about the mixing console. Every event that has a PA or sound reinforcement system, will include this piece of invaluable equipment. Hence, before anything, ask yourself – what is a mixing console?
Well, you are in luck. In today’s article we will be discussing about the various important aspects of the mixing console. You will be able to learn about what the different components of the console are all about, and how they will function in order to help you achieve that picture perfect mix. Hopefully, by the end of this post, you will be confident enough to start mixing!
Introduction – Its purpose
Also referred to as an “audio mixer” or “sound mixer”, the mixing console in audio, is an electronic device used to combine (known as “mixing”), routing, and tweaking the level, tone and dynamics of various audio signals, such as from microphones used by vocalists and mics recording instruments such as drums or percussion. Other signals also include electric or electronic instruments such as the electric guitars or keyboards.
You will find mixing consoles used in numerous applications, including recording audio (in studios), public address and sound reinforcement systems, television broadcasting, and film post-production. An example of a very simple application of the mixing console, is combining signals from two microphones (perhaps used by two vocalists singing a duet) and then sending them to a power amp that drives one set of speakers simultaneously.
For live shows, signals from the mixer typically goes directly to a power amplifier (unless it is connected to powered speakers or the console has a built-in amplifier). A mixer in a nightclub may have 24 channels for mixing the signals from a rock band’s rhythm section and a few singers.
A mixer for a large concert however, may need up to 48 channels, and consoles in very large professional recording studios may need at least 72 channels.
Mixers do not just merely mix signals. Several other functions include supplying phantom power for condenser microphones, pan control (changing the signal’s position in the stereo field), filtering and equalization (low and high cut filters), routing and monitoring options – where various sources can be routed (depends on the mixer) to speakers or headphones for monitoring, without affecting the mixer’s main output.
Let’s look at the various sections that we will be covering today:
- Overall structure (Analog Consoles)
- Channel input strip
- Master output controls
- Hardware routing and patching
- Other features
Overall structure (Analog Consoles)
The structure of a typical analog mixing console, can be divided into three major sections:
- Channel inputs
- Master controls
- Audio level metering
Fundamentally, channel input strips are banks of identical mono or stereo input channels. Every single channel is designed to have rotary knobs, buttons and faders in order to allow the control of “gain” and “equalization” of the signal on each channel. Depending on the mixer’s design and model, a channel may have switches that allows the audio engineer to reroute its signal to various outputs for monitoring.
The master control section allows adjustments of the overall output levels of the mixer. This particular section consists of sub-group faders, master faders, master auxiliary knobs, bus level controls and auxiliary return level controls. Some additional parameters includes solo monitoring controls, a talk-back microphone control, and group muting controls.
Audio level meters (usually meters with needles or LEDs) are simply indicators of the level of an audio signal’s strength. They may be located above the input and master sections of the mixing console, or they could be integrated into the input and master sections themselves. The audio level meters are crucial, as it shows the sound engineer when an audio level starts to “clip” (which is usually unwanted).
Channel input strip
When you take a look at a channel strip on a mixing console, you will realise that it is usually divided into these various sections, in this order (starting from the very top):
- Input jacks (1/4″ jack)
- Microphone pre-amplifiers (XLR input)
- Equalization (semi-parametric, parametric)
- Dynamics processing (compression, gating etc.)
- Routing switches/knobs (aux-sends, panning control, sub-group outputs)
- Input faders
You will find that on most consoles, these different sections are “colour-coded” to make it easier to identify by the operator. Each signal that is patched into the mixer (via its inputs) has its own “channel”. Depending on the mixer’s model, each channel could be stereo or mono. It is almost a universal standard for every mixer to have channels with XLR inputs, RCA or 1/4″ TRS line inputs.
To make it easier for us to further discuss this section, we will divide it into several parts:
- Basic input controls
- Auxiliary send routing
- Channel equalization
- Cue system
- Subgroup and mix routing
Basic input controls
There will normally be several rotary controls (knobs, pots) below the input. The “gain” control is very common and it adjusts the amount of attenuation needed (by adding or cutting gain) to bring the weak signal to a nominal level, suitable for mixing. Most noise of interference is picked up at this initial stage as a result of the high gains involved (about +50 dB, for a microphone signal).
To help reduce interference problems, balanced inputs and connectors, such as XLR or phone connectors, are used. Many mixing consoles may also include “inserts” inputs after the buffer or gain stage.
These provides the flexibility of a “send and return” connection for external processors (outboard gears), which affects only the individual channel’s signal.
Auxiliary send routing
Auxiliary send splits the incoming signal, and sends it to an auxiliary bus, which can then be routed to any external equipment (monitor speakers etc.). Take note that auxiliary sends can either be set to “pre-fader” or “post-fader”. In “pre-fader”, the send level is controlled by the auxiliary send knob, while in “post-fader”, the send level is dependent on the channel’s fader position as well.
Auxiliary sends can be used to send the signal to an external effects processor such as a reverb unit, with the return signal typically routed into a separate channel, or through a designated auxiliary return input. These channels are normally set to “post-fader”. “Pre-fader” auxiliary sends are often used to provide separate signal feeds to performers on-stage (monitor mix), hence it is independent of the main mix that is heard by the audience.
This set of channel parameters allows for the equalization of the channel’s signal by separately attenuating (by “boosting” or “cutting”) a range of frequencies such as, bass, midrange, and treble.
It is almost impossible to not find mixing consoles that at least have a parametric equalizer on every channel. Some come with a built-in, overall equalization unit (either graphic or parametric) at the main output.
You can use this system to listen to one (or multiple) channel’s signal, without interrupting the mixer’s main outputs. Selected signals in the cue system is fed to the mixer’s headphone amp and sometimes, as a “line-level” output, for use with monitor speakers. Terms like “PFL” (Pre Fader Listen) and “AFL” (After Fader Listen) are used to determine where the cue signal is taken from (within the channel’s signal flow).
Most input channels are by default, configured as “PFL”. This allows the engineer to “preview” the channel’s signal without having to route it to any mix. Consoles with a cue feature have a designated switch on each channel, usually labelled as “AFL”, “PFL”, Solo, or Listen. On more advanced mixers, “Solo In Place” (SIP) is a common feature. It is controlled by the Cue button, but disrupts the main output mix.
SIP mutes everything, but leaves out soloed channels. It is often used for trouble-shooting during live shows, where the engineer can easily mute everything else and work on the soloed signal. SIP can be disastrous during a live performance, hence most consoles require deliberate actions (by the operator) to activate SIP mode.
Every channel has a “fader” (sliding volume control) that allows for level adjustment of that channel. The summation of these signals creates the main “mix”. Signals can also be combined on a “bus” to create a submix – a group of channels that can be added for the final mix (For example, multiple guitar signals can be grouped into a bus, and then these guitars can be controlled by one bus fader in the final mix).
Master output controls
You would normally find the subgroup and main output faders together on the right hand side of the mixing board. For most larger consoles however, they are normally around center area, flanked by rows of input channels. Matrix routing is also often found within this “master section”, together with headphone controls and monitoring speaker controls.
Other functions also located in the master section includes, “Talkback” controls (allows interaction with performers through their wedges, or in-ears. For some mixing consoles (although pretty rare), a test tone generator might be included, and located in the same master output section as well. Auxiliary return faders (or knobs) controlling signals returning from outboard processors are also within the same section.
On most mixers, there are at least one VU or peak meters for level indication of each channel and master outputs. It also shows if the signal levels are “peaking” (which causes clipping). Mixers usually have one extra output (at least), other than the main mix. These could be individual bus or auxiliary outputs, often used to output a separate, unique mix to on-stage monitor speakers.
Since humans experience audio levels logarithmically (both amplitude and frequency), the measurement system used on mixing console parameters and displays are almost always in “decibels”. Considering that “decibels” is a relative measurement, and not a unit itself, the meters have to be referenced to a nominal level. The universal “professional” nominal level is set to “+4 dBu” and the “consumer grade” level is “−10 dBV”.
Hardware routing and patching
Some mixing consoles include a “patch bay” (or patch panel). Patch bays are commonly found on recording mixers in studios, but they can also be used for live sound applications. Often times, the microphone and instrument cables from stage, are not plugged directly into the mixer’s pre amps, as this would incur a large number of cables to link sound sources on stage to the mixer.
Instead, cables coming from microphones and instruments on stage are usually patched into the patch bay of a very thick and long snake cable (depends on the make and model), which is then run from the back of the stage to the FOH engineer’s position (where the mixing console is situated). The outputs on the opposite end of the snake (near the mixer) are then plugged directly into the mixer.
There are many makes and models of mixing consoles available out there, and choosing one that best suits your needs can be quite a challenge especially for people who are new to this. Hence, in this section, we will look at a brief summary of what mixers can and cannot do in general.
Most mixers in the market have the capability to:
- integrate external effects (from outboard effects units).
- use mono signals to produce a stereo mix (through pan and balance controls).
- provide phantom power required by condenser microphones.
Some mixing consoles in the market have the capability to:
- create an audible “test tones” using an oscillator. Test tones are useful for troubleshooting issues before the performers arrive and helps identify malfunctioning channels .
- add effects internally (via built-in effects unit).
- read and write console automation.
- be interfaced with computer software or other recording equipment (to allow computer presets to be used, for example).
- control or be managed by a digital audio workstation (DAW) via MIDI or proprietary commands.
- be powered by rechargeable or disposable batteries.
- provide amplifier power for “passive” loudspeakers (also known as “powered mixers”)
Mixing consoles that are designed for broadcasting and live sound reinforcement, normally have the capability for “mirroring” two consoles. This fundamentally makes both of the consoles exact duplicates of one another, with the same inputs and outputs, the same settings, and the same mix.
Two major reasons for doing this is – 1) In case of a hardware failure, a stand-by console is ready to be used and can be switched to (crucial for live broadcasts). 2) It allows sound engineers to set up two identical mix positions, with one at front of house (where the band will be mixed during the show) and the other at a different location within the concert venue. This allows for flexibility, in case the acoustics are unfavourable in the “FOH” position.
That’s all I have for you guys. I hope that after reading this article, you would have at least a stronger understanding of how a mixing console works, and how it will benefit your productions!
Do leave a comment or question below, and share this article if you like!