Audio For Broadcast: The Role Of The Mixing Console

A guided tour through the basics of broadcast audio production workflow using the role of the mixing console and the core areas of its functionality, as a way to explain how it all goes together.

When most people picture an audio control room (ACR), they are most likely picturing the mixing console. It is the mixing console, with all its lights, knobs and fancy sliders, which delivers the wow moment.

The mixing console is the Instagram star and rightly so; it not only has all the bells and whistles, but it literally manages all those bells and whistles too.

Nevertheless, shifts in production workflows are changing this picture. More aspects of live production are being democratised by remote working and by the Cloud, and as more broadcasters embrace distributed workflows, more productions embrace the benefits of flexible working with confidence.

It is in this environment that traditional broadcast mixing console need to keep pace.

Broadcasters As Cartographers

Although broadcasters are already on this road, they are drawing the map as they go. Issues like control latency over Wide Area Networks are largely being managed and the mixing console has already been split into its constituent parts.

The control surface – what everyone thinks of as the mixer – can use on-premise DSP in a traditional way, it can control a DSP engine somewhere else (such as a venue or another broadcast facility), or it can be a hybrid of both.

The control surface no longer needs to be in a studio; it could be anywhere. 

There’s no longer a requirement for a physical surface and control can be on a laptop connected to public internet or using automation to simplify some of the processes.

And while these workflows all take advantage of tapping into traditional processing engines, the hardware which drives the control surface, the continued development and adoption of Cloud-based, scalable microservices will devolve these workflows even more.

Same Old, Same Old

All that said, the audio requirements of live production are unlikely to change.

Despite shifts to distributed working, the broadcast audio console is the hub in the ACR. It manages every audio input and every audio output, and feeds into other equipment such as comms systems, and that will still be true irrespective of whether it is physically central or whether it exists on the edges. Wherever the Operator is based, they will still have the same fundamental responsibilities.

All audio inputs and outputs will still need to be managed; complex and dedicated comms systems will still have to be arranged; all audio signals will still need to be processed appropriately and mixed together in an engaging way; multiple transmission formats will still need to be mixed; outputs will still need to be monitored for intelligibility and international compliance; latency will still have to be mitigated; and most importantly, the whole thing will still need to be guaranteed to stay on air, whatever the connectivity or geography.

Let’s break these down.

Comms & Monitoring

Ensuring that everybody in the production can hear the audio elements of the production that they need to be aware of, and that individuals can communicate easily with the rest of the team are both crucial to the role of audio in broadcast production - which is why they get their own dedicated articles in this series.

Sounding Good

Now everyone in the production is on the same page – thanks comms! - the mixing console turns its attention to managing all the live signals and processing them appropriately so that an audience has a clear narrative to follow.

This is more akin to a traditional mixing console – in fact, it’s what all mixing consoles are designed to do. There are lots of things which affect how incoming sources sound, from the acoustics of the venue to microphone choice and placement. These are all important parts of the planning process which can be mitigated, but in live broadcast there are things which cannot be controlled.

Again, specialist broadcast consoles have features to help with this. For example, high input headroom is an important design principle to counter unexpected and unplanned peaks. Multiple insert points in the signal chain are necessary to introduce external processing, and being able to introduce it at multiple points - whether it’s pre or post-EQ, or pre or post-fader - will affect the end result, so these also need to be considered.

Increasingly, with more pressure on mix operators to mix to multiple output formats, broadcast consoles also need to have assistive applications which can do some of the heavy lifting to allow operators to concentrate on the craft.

Autofader features - or audio-follows-video - allow faders to be opened and closed automatically through GPIO triggers and are well-served in environments where audio sources have to change alongside different camera shots. This is especially popular in fast-paced motorsports where trackside cameras need matching audio to tell the story.

Automix systems, which date back to Dan Dugan’s pioneering automatic mixing system launched in 1974, is often employed on a broadcast mixer to automatically mix the levels of a selection of channels to keep the overall level of the mix constant and ensure a consistent ambient/background noise level.

The Last Leg (And All The Other Legs)

In addition to managing all the comms, managing all the incoming signals, and mixing it all together, the sound desk Operator also prepares the show for transmission.

Transmission outputs used to be simple, with a mono and stereo feed covering all the bases. The last 20 years has seen rapid development with 5.1 surround, immersive formats and individual audio objects all on the table. The uptake in consumer devices which support spatial audio, like Apple’s AirPod Pro and 3D capable soundbars, means that Next Generation Audio (NGA) content like immersive audio and personalisation is heaping more responsibility on the Operator; this is another area where broadcast consoles can help pick up the slack.

NGA is an umbrella term which covers technologies and ideas like immersive and object-based audio (OBA), a technique which encodes audio objects with accompanying metadata to describe what it is and how it contributes to a mix.

Audio objects can contribute to personalisation and accessibility features in consumer equipment and allow the contribution of certain objects to be modified by the viewer. While it’s still early days, real-time transport for this is possible through Serial ADM, a metadata format which can be used for live production.

Immersive sound on the other hand, is already gaining ground, with mixes for live sporting events adding more crowd ambience in the height channels and immersive stings being inserted to add height to replay graphics and in-game statistics.

Broadcast consoles can help with automatic upmixing to multi-channel formats, whether that is for live transmission, or for multitrack ingest into asset management systems for archiving or repurposing.

And of course, they all need to be powerful enough to cope with all the extra stems and be able to flex to cope with the demands of any production schedule.

What’s The Delay?

Delay is an important consideration in a broadcast console, and this can be complicated further when production workflows are geographically distributed. Artificial delay is necessary to compensate for a variety of sync issues, such as video processing delays. Most broadcast consoles will have multiple points where delay can be inserted to bring things back into line. 

As workflows become more geographically diverse, and incorporate more varied environments like on-premise, off-premise and cloud processing, sync will need to be continually assessed and regulated.

Ready For Anything

We often say the broadcast industry is in transition. In fact, it’s always been in transition.

The adoption of IP infrastructures and a renewed focus on remote working and virtualization has changed how we look at broadcast infrastructures, but in essence the same challenges need to be met and the fundamentals of those workflows remain unchanged.

Control is still paramount, reliability and redundancy are still key components, and an operator still needs to manage all the audio in a simple and ergonomic way where they have access to every parameter and can adapt on the fly wherever the broadcast demands.

However, that is done and in whatever context that is, the mixing console will continue to be the technology which holds everything together.

It just might look at bit different.

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