Audio For Broadcast: Monitoring, Mix Minus & Comms

In parallel to its role entertaining the audience via the programme output, audio is the central nervous system of all broadcast infrastructure, ensuring everybody can hear what is happening and communicate with each other - without it everything rapidly breaks down.

Peter Drucker, the founding father of modern management studies, very wisely said that “the most important thing in communication is hearing what isn’t said.”

He’s right of course.

But in a broadcast environment the most important thing in communication is, in fact, not that. It’s hearing what is said. Communication is the single most important aspect of any production. Good intercoms are too often taken for granted but without them a broadcast studio is made up of groups of people frantically waving at one another off camera.

Intercoms and signal monitoring are less about what a signal sounds like and more about how those signals are managed, shared and distributed between all the people who play very specific roles in getting a programme to air.

Intercoms are partly about guaranteeing a quality of service, partly about ensuring everyone is where they need to be and partly about making sure everyone knows what’s going on.

Let’s Talk

People in a production environment are scattered and reliable communications keep everyone on top of their game. This is even more important when productions are split across multiple sites or have people on location who don’t have access to a screen.

The most casual of glances at the credits on a live show illustrates how many people need to be kept across the live production; talent, camera operators, sound assistants, studio technicians, floor managers, directors, lighting engineers, guests, runners, show callers and more all need to know what’s going on.

If a camera goes down, how does the talent know to look into another? How does a reporter on an airstrip in Dubai know when to answer a question? Or what that question is?

Some people will need to hear everything while others will need more exclusive communication links. The Director might need a two-way conversation with the Producer, or with a Production Assistant who is looking after a special guest. Some people will need discreet in-ear monitors (IEMs), some crew members will need two-way radios, and the talent or the audience might need foldback speakers. They might be wired, they might be wireless; they might warrant private intercoms from A to B, or they might need intercoms from A to B, C, D and E.

For this reason, intercom systems have to be extremely flexible. Helpfully they fall into three basic classifications: partyline (sometimes referred to as simply PL), matrix and wireless communications.

Unhelpfully, most broadcast infrastructures will use all three at the same time.

Party Time On The Partyline

A partyline is no place for secrets.  They are two-wire networks which use standard three pin XLR cables to allow full duplex communications, which is a fancy way of saying that multiple people can talk at the same time and everyone can hear everyone else.  This makes them useful for communicating to groups of people who all have to be across the same thing, such as camera, audio or lighting crews.

They employ distributed amplifiers so they can be used with Y-cable splitters with no loss to the signal, they can be daisy-chained together and compact intercom panels can be located in various locations around a production infrastructure. This makes them extremely scalable and adaptable to different broadcast environments.

Partylines are quick to set up and useful to keep groups informed, providing two-way communication (talk as well as listen) over a single cable between all end points with everyone involved in the same conversation. If you talk on a partyline everyone hears you.

Let’s Get Moving

Partyline endpoints can also be accessed using wireless intercom belt-packs and headsets to provide more freedom of movement. This can be useful if your role isn’t in a static location and you are required to go wherever the production demands are, or if you are on location at a sports event or outside broadcast. Belt-packs can also be daisy-chained together in the same fashion as wired intercoms.

Handheld radios are the other main method of wireless communications on set and are often used to provide communications across larger sites for people who require the freedom to roam. They are cheap and they are very flexible; they can be set up in a variety of ways, ranging from a simple radio to radio configurations to wider connectivity via radio interface units.

Radio to radio arrangements use the same radio frequency for transmit (talk) and receive (listen) and can only communicate in one direction at a time; this means that if you are talking you can’t listen at the same time, and it also locks out other radios from communicating. This is known as a simplex connection, and it how a standard two-way walkie talkie operates.

But handheld radios can also be connected to the wider network, including a partyline, and can even be set up to use different frequencies for talk and listen; this is known as semi-duplex. This means that they can always receive messages regardless of whether another is transmitting, which means that key personnel can always be heard, and on every radio.

In The Matrix

A matrix interface system is more complex. In the matrix, everything goes and matrix interface panels do it all. They are compact panels which can be rack mounted or located on a desktop to provide flexible access to individuals or groups of people scattered around the broadcast environment.

A matrix intercom system allows cross communication with many different communication tools. They allow for direct communications between panels as well as to partyline and wireless communications. Buttons can be programmed to talk or listen to anything connected to the system and they manage all intercoms including GPIOs and access to interruptible foldback mixes (IFBs).

Can I Just Interrupt Here?

IFB mixes are central to broadcast intercoms. They are commonly known as a mix-minus because they enable a full mix to be sent to multiple listeners but minus their own input. This is really useful, especially for crew members and talent who are on location at a venue or on an outside broadcast. It’s vital because it allows them to hear the broadcast audio without hearing their own delayed voice, which will inevitably be delayed due to the distances involved making the round trip to the studio and back. For example, a field reporter on a news item needs to hear the programme output while communicating with the news anchor, and mix-minus removes the reporter’s own (delayed) voice from the mix.

The mix minus bus is so useful that broadcast consoles always have mix minus busses built in, which means a sound operator doesn’t have to build time-consuming multitrack mixes to achieve the same result – it’s one button press away, for absolutely anyone who needs it.

What Piffle!

There are other handy features built into the broadcast console to ensure we all keep talking. PFL stands for pre-fade listen and is a monitoring function you will find on even the tiniest of broadcast desks. The PFL button creates an audible check on an integrated speaker, a headphone output or the main monitor speakers which enables an operator to check an incoming feed before it is fed into the mix when the fader is opened.

It’s a useful confidence monitor to pre-hear an outside source to make sure it’s still live, as well as an opportunity to check its signal level so that the right amount of gain can be applied on the channel input so it works with the rest of the mix.

Feeding The Beast

The mixing console also plays another key role. In fact, it is central to everything.

In addition to managing the broadcast mix, it is stuffed to the brim with every single audio signal flowing through the production, making it ideally placed to generate all the audio stems to feed into the intercom system.

But it is the intercom system which provides the fabric, managing the flow of those signals and creating the interrupt when that all-important IFB goes to the talent’s earpiece. It is the intercom system which provides the ability to talk to anyone else in the production environment, and depending on how things are set up, does so for anyone with access to a panel, belt-pack or radio.

Many intercom systems now utilise standard IP protocols like AES67 or Dante, which simplifies connectivity and squeezes more signals down a single cable, while more adaptability is being created with initiatives like TFT touchscreens, programmable channels and Bluetooth connectivity, but the principal of broadcast communications haven’t changed.

Reliable communication is essential to guarantee the smooth operation of every broadcast, at all levels, and in this case that still means hearing everything that is said.

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