Stage Audio & IEM Systems

Introduction

On a big show the stage is a system in its own right. Ninety inputs arrive through stage boxes on a network. A dozen performers wear in-ear packs fed by transmitters in a rack. Thirty radio channels share a slice of spectrum that also carries television, and every one of them has to stay clear for two hours. None of that is the mix, and all of it has to work before a mix is possible.

The people who make it work are stage technicians -- A2s, monitor technicians, RF technicians -- and this book is about their side of the job. It covers the in-ear system from the console output to the performer's ear, the radio spectrum and how to share it, the stage inputs and how to keep ninety of them right, and the interface with the band's own equipment.

It also covers building a performer's in-ear mix and protecting their hearing, because on many shows the stage technician is the one who fits the earpieces, hands over the pack and hears the first complaint. This book teaches the stage side of building those mixes: checking them, handing them over and keeping them safe.

The equipment is named throughout. A stage technician is handed a PSM1000 pack or asked to patch a Rio3224 and is expected to know what it is. That vocabulary is part of the job.

How to Use This Book

The first four chapters follow the in-ear system from the console to the ear. The next two cover radio. The following two cover the stage inputs and the band's equipment. The last three are about running the stage through a show, diagnosing what goes wrong, and building a career on it.

Each chapter ends with a reference table, a procedure, a failure table written symptom first, a practical exercise and a checklist.

Keep a notebook

Write down the frequencies you coordinated and in which building, which pack went to which performer, the earpiece each one uses, the antenna positions that worked, and the stage plot as it actually ended up rather than as it was drawn. Spectrum changes from city to city and the stage changes from day to day; the notebook is what makes the second show quicker than the first.

A note on the words

A body-worn receiver is a beltpack to some people and a bodypack to others, and both name the same object. In-ear monitor, IEM and in-ears all name the same system. Coordination and scanning are related but not identical: one is choosing the set of frequencies that can coexist, the other is finding out what is already in the air. This book uses the words most widely understood and names the alternatives where they matter.

A note on safety

You are handling somebody else's hearing. On many shows the stage technician fits the earpieces, hands over the pack and hears the first complaint, which makes the level going into a performer's ear your responsibility rather than theirs: check the limiter before the pack leaves your hands, and bring a mix up rather than starting loud. Protect your own hearing across the whole day as well, and leave antenna masts and anything carrying weight above head height to somebody trained to put it up.

Where this book sits

This book assumes you have read A2 & Stage Audio Fundamentals and Audio Intermediate, or that you already know what is in it.

If none of that is true yet, read A2 & Stage Audio Fundamentals first.

What pairs with this

• Dante Level I–III — the audio network the stage boxes run on
• Backline Technical — the band's side of the backline interface

Where it leads

These are not steps in an order. Take whichever one fits.

• Wireless & RF Systems — radio coordination and spectrum in depth
• Monitor Engineering — mixing for the performers whose in-ears you look after

In-Ear Monitor Systems

An in-ear monitor system takes a mix from the monitor console and delivers it into a performer's ears, usually by radio. It is a chain of five or six pieces of equipment, and every fault a performer will ever report lives in one of them.

IEMs put a personal, isolated mix in each performer's ears — the modern standard.

What IEMs are and why

In-ear monitors replace floor wedges with earpieces. The performer hears a personal mix directly, sealed from the stage, at a level far lower than a wedge would need. The feedback loop between wedge and microphone disappears, stage volume drops, and the performer hears the same mix wherever they move.

For the stage technician the change is just as large. A stage of wedges is loudspeakers and cable. A stage of in-ears is a radio system: transmitters, antennas, bodypacks, batteries and earpieces, each with settings that must be right and each able to fail in the middle of a song.

The IEM signal path

The path runs in a fixed order, and knowing it is how you find a fault quickly. The monitor console sends a stereo mix out of an output. That output feeds a transmitter in a rack beside the desk. The transmitter sends the mix out as radio through an antenna -- usually through a combiner shared with other transmitters. The performer's bodypack receives it, decodes it and feeds it through a volume control and limiter to the earpieces.

• Console output -- a stereo bus carrying the performer's mix.
• Transmitter -- turns the mix into a radio signal on one frequency.
• Combiner -- lets several transmitters share one antenna.
• Antenna -- sends the signal across the stage.
• Bodypack receiver -- worn by the performer, tuned to that frequency.
• Earpieces -- the last link, and the one the performer handles.

When a performer says their in-ears have gone wrong, walk the path. Is there signal on the console output meter? Is the transmitter showing audio? Is the pack showing radio signal strength? Is the pack's volume up? Does a spare earpiece work? The first link that fails that test is where the fault is.

Wireless and hardwired systems

Most in-ear systems are wireless, because performers move. But a drummer on a riser or a keyboard player behind a rig does not move, and for them a hardwired system is simpler and more reliable: the console output feeds a small amplifier or a wired bodypack by cable, with no radio at all.

Shure's P9HW is a wired bodypack: the same kind of pack, mix controls and limiter a player would use wirelessly, fed by cable instead of radio. A headphone amplifier on the drum riser does the same job more simply. Either way, one less radio channel is one less frequency to coordinate and one less thing to drop out.

The in-ear systems you will meet

Shure's PSM1000, with the P10T transmitter and P10R bodypack, is the touring standard on a very large proportion of professional stages, with the PSM900 and PSM300 beneath it. Sennheiser's 2000 series, built around the Sennheiser SR 2050 transmitter, and the ew IEM G4 are equally familiar, and Wisycom systems appear on high-end productions and in broadcast.

A stage technician should be able to pick up any of them and find the frequency, the RF power, the stereo or mono setting and the limiter without looking anything up. The menus differ; the settings are the same everywhere.

The in-ear signal path

Walk it in order when anything goes wrong.

How to do it

1. Confirm the console output meter shows the mix.
2. Confirm the transmitter shows audio and is on the right frequency with RF on.
3. Confirm the pack shows radio signal and has battery.
4. Confirm the pack volume is up and the limiter is not clamping.
5. Swap the earpieces for a known-good pair.
6. Fix the first link that fails; do not skip ahead.

What goes wrong

Practice it

With any wireless in-ear system.

Transmitters, Packs and Antennas

Most in-ear trouble is radio trouble, and most radio trouble is settings and antennas. This chapter covers the pieces that turn a mix into a radio signal and back again, and the choices that decide whether it survives the trip across a stage.

Transmitter settings

Every in-ear transmitter has a small number of settings that matter. The frequency decides where in the spectrum the mix travels, and it must come from a coordinated plan, never from a guess. The RF power -- commonly 10, 50 or 100 milliwatts -- decides how strong the signal is. The audio mode decides whether the mix is sent in stereo or mono.

More power is not automatically better. A 100 milliwatt transmitter reaches further, and it also raises the level of intermodulation products that interfere with every other system on the stage. Use the lowest power that reaches every position the performer uses. On a small stage that is often 10 milliwatts.

Stereo mode sends a proper stereo mix but needs a stronger signal to be clean; mono is more robust at range. For a performer who roams a large stage, a clean mono signal can be better than a stereo signal that breaks up at the edges.

Bodypack settings

The bodypack -- often called a beltpack, because it clips to the performer's belt -- must be tuned to the transmitter's frequency, and the quickest way is to sync them: most systems scan for a clear channel on the transmitter and pass the setting to the pack by infrared. Shure's packs sync with an infrared window; Sennheiser's do the same. After syncing, always confirm the numbers match.

The pack has its own limiter, which should be on, and a volume control the performer uses. Some packs offer a mix mode -- Shure calls it MixMode -- in which the two channels of the transmitter are treated as two separate mono mixes, one being the band and one being the performer themselves, and the pack's balance control lets the performer set how much of each they hear.

Batteries matter more in a bodypack than anywhere else. Many current packs run on dedicated rechargeable batteries, such as Shure's SB900 in the P10R; others take AA cells. Either way, every pack starts every show freshly charged or with new cells, whatever the meter says.

Antennas and polarisation

The small whip antenna fitted to a transmitter works on a small stage. On anything larger, the transmitter feeds a remote antenna mounted where it has a clear view of the performers -- usually at the side of the stage, above head height, pointed across the space they use.

Paddle antennas are directional: they concentrate the signal in the direction they point. Helical antennas are directional too, and they transmit with circular polarisation. That matters because a performer moving and turning constantly changes the angle of the antenna in their pack; with an ordinary antenna that angle can cause the signal to fade, but a circularly polarised signal is received equally well whatever the angle. That is why the helical is the standard antenna for in-ears on professional stages.

Line of sight is the rule that matters most. Radio at these frequencies does not like passing through people, metal or LED walls. An antenna with a clear view of the stage beats a more powerful transmitter with a poor view.

Combiners and antenna distribution

Several transmitters cannot simply be connected to one antenna, and several antennas side by side interfere with each other. A combiner takes the outputs of several transmitters and merges them onto a single antenna cleanly. Shure's PA411 combines four and the PA421B eight; Sennheiser's AC 3200-II does the same job.

Wireless microphone receivers face the opposite problem: many receivers need the signal from one pair of antennas. An antenna distribution unit -- such as the Shure UA845 -- splits the antenna signal to several receivers.

Keep the two apart. In-ear transmitter antennas are sending strong signals; microphone receiver antennas are listening for weak ones. Place them several metres apart and not pointing at each other, or the in-ear transmitters will overwhelm the microphone receivers.

Antenna types

The helical is the in-ear standard for a reason.

Combining and distributing

Transmitters combine; receivers distribute. Keep them apart.

How to do it

1. Take frequencies from the coordinated plan, never by guessing.
2. Set each transmitter's RF power to the lowest that covers the stage.
3. Choose stereo or mono for each performer's range.
4. Combine the transmitters and feed a helical antenna with a clear view of the stage.
5. Sync every pack, confirm the numbers match, and enable every pack limiter.
6. Place the transmitter antenna several metres from the microphone receiver antennas.

What goes wrong

Practice it

With two in-ear systems and a stage to walk.

Earpieces

The earpiece is the last link in the chain and the only one the performer touches all night. It decides whether the mix sounds full or thin, whether the performer is comfortable for two hours, and -- because it lives in an ear -- it needs looking after in a way no other piece of stage equipment does.

Drivers, and why earpieces sound different

An earpiece contains one or more tiny loudspeakers called drivers. Dynamic drivers are small conventional cones and are good at low frequencies. Balanced armature drivers are tiny, precise and efficient, and professional earpieces often contain several of them, each handling part of the frequency range, with a small crossover inside the shell.

More drivers is not automatically better, but it usually means more detail and a more even response at the level performers use. The Shure SE846, for example, uses four balanced armature drivers. Budget universal earpieces such as the SE215 use a single dynamic driver and are perfectly usable for many performers.

Universal and custom fit

Universal earpieces fit anyone, sealed by foam or silicone tips in several sizes. The right tip is the one that seals without pain, and it is often a different size in each ear. Foam tips seal well and wear out; silicone tips last but can seal less reliably.

Custom-moulded earpieces are made from impressions of the performer's ear canals, taken by an audiologist, and built by makers such as JH Audio, Ultimate Ears, 64 Audio and Westone. They seal the same way every time, stay in place when the performer moves, and are comfortable for long shows. For anyone on in-ears every night they are the professional standard.

A custom earpiece that no longer seals -- because the performer's ears have changed, or the shell has worn -- behaves like a badly fitted universal, and the performer will describe it as the mix going thin. Impressions should be retaken every few years.

Cables, spares and hygiene

Earpiece cables are thin and are worn, pulled and trodden on every night. They fail, usually intermittently at the connector. Keep a spare cable for every detachable earpiece, and a complete spare pair of universal earpieces for every performer, cleaned and ready.

Earpieces go into ears, so they must be cleaned. Wipe them after every show with a suitable cleaning wipe, keep each performer's earpieces in their own case, and never share them between people without cleaning. Foam tips are single-person and are replaced rather than cleaned. An ear infection can stop a performer working, and it is avoidable.

Impressions and the audiologist

Custom earpieces begin with ear impressions taken by an audiologist: a soft material is injected into the ear canal, allowed to set, and removed as an exact cast. The maker scans or casts it and builds the shell to match. The appointment usually takes half an hour, and many audiologists who work with musicians also run a hearing test at the same visit.

Impressions are taken with the mouth slightly open, often with a bite block, because the jaw moves the ear canal when a singer opens their mouth. An earpiece moulded with the mouth closed can lose its seal the moment the performer sings a wide vowel.

Build times run to several weeks, so a performer moving to in-ears for a tour needs impressions taken well before rehearsals. Until the customs arrive, a well-fitted universal is the working solution.

Earpiece types

The seal matters more than the driver count.

How to do it

1. Try tip sizes in each ear until each seals without pain.
2. Confirm the seal by listening for the low end to appear.
3. Keep a spare cable and a spare universal pair for every performer.
4. Clean every earpiece after every show, and store each performer's separately.
5. Replace foam tips rather than cleaning them.
6. Recommend new impressions when a custom earpiece stops sealing.

What goes wrong

Practice it

With a set of universal earpieces and several tip sizes.

Building & Dialing In IEM Mixes

On many shows the stage technician fits the earpieces, hands over the pack and hears the performer's first reaction. This chapter is the stage side of building an in-ear mix and keeping it safe.

Each performer needs their own mix, set right and at a safe level.

Building a performer's IEM mix

A performer's monitor mix for in-ears starts from what they need to play in time and in tune: a time source such as the drums or a click, a pitch source such as a keyboard, and their own voice or instrument clearly. It is stereo, with sources panned roughly where they stand on stage, which makes each one easier to hear at a lower level.

From the stage side, building the mix is mostly a matter of checking it arrives as intended. Listen on a matching earpiece to what the performer hears; confirm the click is present only where it should be; confirm the ambience microphones are working; and hand the pack over at a moderate volume setting.

IEM levels and protecting hearing

In-ears deliver sound directly into the ear canal, sealed, for two hours a night. That makes level a health matter. Hearing damage depends on both level and time: safe exposure time halves for every 3 decibels of extra level (the NIOSH guideline is eight hours at 85 dBA, four hours at 88 dBA, two hours at 91 dBA), so a mix a little too loud every night for a tour does lasting harm.

The protections are layered. A limiter on the console output, a limiter in the transmitter where available, and the limiter in the bodypack, all enabled. A clear mix, so the performer has no reason to turn up. A moderate starting volume on the pack when it is handed over, noted so that creep can be spotted.

Performers who use in-ears every night should have their hearing tested by an audiologist regularly, starting with a baseline test before the tour. The same audiologist often takes the impressions for custom earpieces, which makes it a natural appointment to keep.

Ambience microphones on stage

Sealed in-ears cut the performer off from the room. Ambience microphones give it back: a pair of microphones at the front corners of the stage, pointed at the audience, fed into the in-ear mixes. Small-diaphragm condensers or short shotgun microphones such as the Sennheiser MKH 416 are common choices.

Place them where they hear the audience more than the PA -- low, at the stage lip, pointed out and slightly down -- and keep their cables clear of the performers' path. A stage technician who knows why they are there places them well.

Personal mixers and hardwired feeds

Some performers mix their own in-ears from a personal mixer, such as the Allen & Heath ME-1 or Behringer P16-M, fed a set of stems from the console over a network cable. The stage technician's job is to place the mixers where the players can reach them, run the network, and make sure the stems arrive.

Drummers and keyboard players who do not move are often better on a hardwired feed: a wired bodypack or headphone amplifier fed directly by cable, with no radio to drop out.

Layers of hearing protection in an in-ear system

No single layer is enough on its own.

How to do it

1. Confirm the pack is synced, charged and limited.
2. Fit the earpieces and confirm the seal.
3. Listen on a matching earpiece to their mix.
4. Confirm the ambience microphones and the click are where they should be.
5. Set the pack to a moderate volume and note the setting.
6. Show the performer where the volume and any mix-mode balance are.

What goes wrong

Practice it

With an in-ear system and a colleague acting as performer.

The Radio Spectrum on Stage

Every wireless microphone and in-ear pack on a stage uses a slice of the radio spectrum, and that spectrum is shared -- with television, with mobile networks, and with every other production nearby. A stage technician does not need to be a radio engineer, but they do need to know where wireless is allowed to live and why frequencies cannot be chosen at random.

UHF, and why it is crowded

Most professional wireless microphones and in-ear systems work in the UHF band, in the same range as digital terrestrial television. Wireless production equipment is allowed to use the gaps between television channels in any given area -- often called white space -- which is why the usable frequencies change from city to city.

That space has been shrinking for years, as governments have sold parts of the UHF band to mobile phone networks. The same number of systems now has to fit into less spectrum, which makes careful coordination more important every year.

Some systems work outside UHF altogether: in the 1.9 GHz band used by DECT-based systems, and at 2.4 GHz. These can be useful on crowded shows, with their own trade-offs in range and latency.

Licensing, and the bands that were sold

The rules differ by country, and the regulator is the authority. In the United States the Federal Communications Commission licenses professional users under its Part 74 rules and allows some unlicensed operation; in the United Kingdom Ofcom issues programme-making and special events licences, including for the shared channel 38. Most other countries have an equivalent.

In the United States the 600 MHz band -- roughly 614 to 698 MHz -- was auctioned to mobile networks, and wireless microphones and in-ear systems may no longer operate there. In Europe the 700 MHz band went the same way. Equipment built for those ranges is still sold second hand and still turns up in rental stock; using it is illegal and, increasingly, simply does not work because the band is full of mobile traffic.

The practical rule for a stage technician: know the tuning range of every system on the stage, know which parts of it are legal where you are, and never accept a frequency that falls in a sold band.

Intermodulation

When two or more transmitters operate near each other, their signals mix inside the equipment and produce new signals on frequencies nobody chose. These are intermodulation products. The strongest, the third-order products, fall at twice one frequency minus the other: two transmitters on 600 and 601 MHz produce interference on 599 and 602 MHz.

With two transmitters that is manageable. With thirty, the number of intermodulation products runs into the thousands, and any system tuned to one of them suffers interference. This is why frequencies cannot be picked one by one: they must be calculated as a set, so that no system lands on a product of the others.

In-ear transmitters make intermodulation worse because they are transmitters, operating at higher power and often side by side in a rack. Coordinating them in their own part of the band, away from the microphones, is standard practice.

How radio behaves on a stage

At UHF frequencies radio travels roughly in straight lines and reflects off hard surfaces. On a stage that means the signal reaching a receiver arrives by several routes at once -- directly, and reflected off the floor, the set, the truss and the LED wall. Where those copies arrive out of step they cancel, and the signal drops out at that spot. Move a few centimetres and it returns.

People absorb UHF well, because a human body is mostly water. A performer's own body between their pack and the antenna can cost a surprising amount of signal, which is why a bodypack worn at the back and a performer facing away from the antenna is a classic dropout. Metal and LED screens block and reflect it.

Diversity reception

Professional wireless microphone receivers use diversity: two antennas a short distance apart, with the receiver choosing or combining whichever is receiving the better signal at each moment. Because a dropout from cancellation happens at one spot, the second antenna, a little way off, is very unlikely to be in a null at the same instant.

This is why receiver antennas come in pairs and why they should be spaced apart rather than bundled together. Most in-ear bodypacks have only one antenna each -- touring packs such as Shure's P10R, with two antennas for diversity, are the exception -- which is one reason in-ear coverage depends so heavily on good transmitter antenna placement and circular polarisation.

Other bands, and when to use them

Outside UHF, systems in the 1.9 GHz band -- based on the DECT standard -- are popular for conferencing and corporate work because the band is licence-free in many countries and the systems coordinate themselves. Their channel count and range are more limited, and the audio is more compressed.

Systems at 2.4 GHz share the band with Wi-Fi and Bluetooth, which makes them convenient and also vulnerable in venues full of phones. On a crowded production, putting some less critical systems in these bands frees UHF spectrum for the lead vocal and the in-ears.

The spectrum on stage

Rules differ by country. The regulator is the authority.

How to do it

1. List every wireless system and its tuning range.
2. Mark any range that overlaps a sold band.
3. Confirm the licensing requirements where you are working.
4. Remove or retune anything that cannot operate legally.
5. Pass the remaining list to whoever coordinates frequencies.

What goes wrong

Practice it

With the equipment list of a real show.

Coordinating Wireless at Scale

Thirty radio channels on one stage is not thirty radios. It is one system, and it is planned as one: scanned, calculated, assigned, tested and backed up before the first microphone is handed out.

Scanning the room

Coordination begins with a scan: a sweep of the spectrum at the venue to see what is already there. Television transmitters, other productions, broadcast trucks and LED walls all show up. The scan is done at the venue, with the stage equipment powered up, because the LED screens and lighting on the stage itself are often a source of noise.

Many receivers can scan on their own. A dedicated spectrum analyser such as an RF Explorer gives a clearer picture and can be walked around the stage to find where the noise is coming from.

Coordination software

The scan feeds coordination software, which calculates a set of frequencies that avoid the occupied spectrum and each other's intermodulation products. Shure's Wireless Workbench and Sennheiser's WSM are the tools in most common use, and both can push the chosen frequencies directly to networked receivers and transmitters.

The software's plan is only as good as its inputs: every system must be entered, including the ones belonging to the support act, the broadcast crew and the venue. A coordination that leaves out the local news crew's radio microphones has not been done.

Always ask the software for spare frequencies as well. A backup frequency for every critical system, already calculated to be compatible, turns a mid-show interference problem into a thirty-second retune.

Wireless microphones as stage inputs

Most lead vocalists and every presenter arrive on a wireless microphone, and on a large show there may be twenty or more: handhelds, bodypacks with lavalier or headset microphones, and instrument packs for guitarists who move. Each one is a radio input to the stage, with a receiver in the rack, an antenna and a battery.

The systems named on riders are Shure's Axient Digital -- the Shure Axient Digital AD4Q is a four-channel receiver you will see in many racks -- and ULX-D and Sennheiser's Digital 6000 at the top, with Sennheiser's EW-DX and Shure's SLX-D below. Rental houses carry them for the same reasons consoles are standardised: engineers know them and riders ask for them.

RF coordination at scale -- the running plan

On a festival or a large event the RF coordinator is a job of its own, and every act's wireless is registered in advance and assigned frequencies before arrival. On a smaller show the stage technician may do it. Either way the plan is written down: every system, its frequency, its backup, its owner and its battery schedule.

During the show, the coordinator or stage technician watches the receivers' signal meters and the spectrum. A receiver showing falling signal strength or rising noise before the performer notices anything is the warning, and the backup frequency is the answer.

Placing receiver antennas

Wireless microphone receivers need their antennas where they can see the stage: usually paddles at the front corners or the sides, above head height, pointed at the area where the performers work, and spaced apart for diversity. Receivers in a rack at the side of the stage with whips on the back see mostly the inside of a road case.

Remote antennas are connected by coaxial cable, and coaxial cable loses signal with length and frequency. Use low-loss cable, keep runs as short as the placement allows, and use an antenna booster only to make up for cable loss, not to add gain the system does not need -- too much gain overloads the receivers and makes intermodulation worse.

The festival RF office

At a large festival or a multi-stage event, one RF coordinator or a small team manages the whole site. Every act submits its wireless list in advance: models, tuning ranges and quantities. The coordinator assigns frequencies for every stage so that no two systems on the site collide, and publishes the plan.

On arrival, each act's stage technician reports to the RF office, confirms the plan, and tunes their equipment to the assigned frequencies. An act that turns up and switches on unplanned equipment can take out another stage's lead vocal. Following the festival plan exactly is not optional.

Watching the RF during the show

Coordination software can monitor every networked receiver live: signal strength, audio level, battery and interference, all on one screen. The person watching it sees a failing battery or a rising noise floor before the performer does, and can switch to a backup frequency or bring a spare between songs.

Log every event during the show -- a dropout, a battery warning, a retune -- with the time and the system. The log is how the cause is found the next day, and how the plan improves for the next show.

The wireless systems you will meet

Rider vocabulary for radio microphones and in-ears.

The coordination toolkit

Scan, calculate, assign, test, back up.

How to do it

1. Collect every system on the show, including support acts, broadcast and venue.
2. Scan at the venue with the stage equipment powered.
3. Enter everything into coordination software and calculate frequencies with backups.
4. Push or enter the frequencies and confirm every system matches the plan.
5. Walk the stage with every microphone and pack during line check.
6. Keep the written plan at the rack and watch the meters during the show.

What goes wrong

Practice it

With coordination software and at least four wireless systems.

Advanced Stage Audio

A large show can have ninety or more inputs. Every one of them must reach the right channel, cleanly, every day, often patched in the dark by people who were not there yesterday. That only works with a system.

Bigger shows mean more inputs, more wireless, and more to coordinate.

Complex input management

The input list is the foundation: every source numbered, with its microphone or DI, its stand, its stage box input and its console channel. On a large show it is kept as a spreadsheet and printed as a patch sheet for the stage.

The discipline is that the channel number and the stage box input agree wherever possible, and that nothing is changed on the stage without being changed on the sheet. The sheet on the stage and the sheet at the console must be the same version, dated.

RF coordination at scale and backline

A big show puts dozens of wireless microphones and in-ear mixes on the stage at once, and every one of them needs a frequency that is compatible with all the others. They are coordinated together, as one plan for the whole stage, never one system at a time; the previous chapter covers how.

The instruments themselves -- amplifiers, keyboards, drums, playback -- belong to the backline technicians, and every one of them is also a source for the audio system. Where the two worlds meet is the subject of the next chapter.

Stage boxes on the network

The stage end of a modern console is a stage box on an audio network: the DiGiCo SD-Rack, the Yamaha Rio3224-D2, the Allen & Heath DX168 and many others. Each carries a block of microphone inputs and line outputs, and sends them to the console over Dante, MADI, Optocore or the manufacturer's own protocol.

Two cautions follow. The preamplifiers are in the stage box, so the gain is set remotely from the console -- which is why gain ownership on a shared network must be agreed. And the network is now a single point of failure, which is why large shows run redundant network links between stage and console.

Splits

When two or more consoles need the same inputs -- front of house, monitors, a broadcast truck, a recording -- the inputs must be split. A transformer split, such as a Radial OX8-j, gives each destination an electrically isolated copy with no shared ground, which prevents hum between systems. An active split does the same electronically. A digital split shares the network stage box among consoles.

Broadcast and recording trucks usually want an isolated transformer split even when the production uses a digital network, because it keeps their system completely separate from the stage.

Sub-snakes, labelling and colour coding

Rather than running ninety individual cables to the stage box, the stage is divided into areas, each served by a sub-snake: a short multicore with a small box at the instrument end. The drum kit gets one, the keyboard rig another. Changeovers become a matter of connecting a few multicores rather than dozens of cables.

Labels do the thinking in the dark. Every cable end carries its input number; every sub-snake box carries its range; colour coding identifies areas at a glance. A stage that is labelled well can be patched correctly by a crew member who has never seen it.

The input list at scale

On a large show the input list is a spreadsheet with a column for every fact a crew member might need: channel, source, microphone or DI, stand, phantom power, stage box and input, sub-snake, split, and notes. Printed, it becomes the patch sheet on stage and the reference at every console.

Keep the source names identical everywhere: on the spreadsheet, on the console channel names, on the cable labels. "Kick In" on the sheet, "KICK IN" on the desk and "BD1" on the tape is three names for one thing, and at two in the morning in a changeover someone will get it wrong.

Redundancy on the stage network

Once the stage runs on a network, one broken cable can silence every input at once. Large shows therefore run redundant links: two separate network paths between the stage boxes and the consoles, often on separate switches, so that if one fails the other carries on without interruption.

Dante does this with primary and secondary networks; MADI and Optocore systems do it with redundant fiber or ring topologies. The stage technician's part is to keep the two paths physically separate -- different routes, different cable ramps -- because two redundant cables tied together fail together when a forklift runs over them.

Stage boxes and splits

The stage end of every modern show.

How to do it

1. Print the dated patch sheet and give the same version to the console.
2. Place sub-snakes by area and label their input ranges.
3. Patch every source to its sheet position, labelling both ends.
4. Confirm redundant network links between stage boxes and consoles.
5. Line check every input against the sheet.
6. Record every change on the sheet the moment it is made.

What goes wrong

Practice it

With a real input list of forty or more inputs.

The Backline Interface

The backline is the band's own equipment: amplifiers, keyboards, drums, playback computers. It is where the band's world meets the audio system, and most of the noise, hum and mystery faults on a stage start at that boundary.

DI boxes

A DI box converts an instrument's unbalanced output into a balanced microphone-level signal the stage box can accept over a long cable. Passive DIs, such as the Radial JDI, use a transformer and need no power; they are robust and suit active sources such as keyboards. Active DIs, such as the Radial J48 or the Countryman Type 85, need phantom power and suit passive instruments such as many bass guitars and acoustic pickups.

A stereo keyboard needs two DIs or a stereo DI such as the Radial ProD2. The ground lift switch on a DI breaks the audio ground between the instrument and the system and is often the first cure for hum.

Amplifiers and keyboard rigs

Guitar and bass amplifiers are usually miked, sometimes also taken by DI. Keyboard rigs are all DI and often large: several instruments, a submixer, a computer running software instruments. Agree with the band's technician which outputs you are taking and whether you are taking them before or after their own mixer.

The backline technicians are the stage technician's closest allies. They know the band's equipment intimately, they will tell you when something has changed, and they are usually the ones who move the wedges and swap the batteries during the show.

Playback rigs and redundancy

Many shows run backing tracks, click and cues from a computer, very often Ableton Live. Because the whole show depends on it, the standard practice is two computers running identical sessions in sync, feeding a redundancy switcher such as the Radial SW8 or an iConnectivity PlayAUDIO12, which switches to the backup automatically if the main computer stops.

The playback rig's outputs -- click, tracks and cues -- arrive at the stage box like any other inputs, and the click must be patched only to the destinations that should receive it.

Stage power, ground loops and hum

Hum on stage is almost always a ground loop: two pieces of equipment connected by audio and also each connected to mains earth by different routes, so a small current flows in the audio screen. The cure is to break the loop in the audio path -- with a DI's ground lift or an isolation transformer -- never by removing the mains earth, which is the safety connection that stops equipment becoming live.

Prevention is better. Power the audio equipment on stage from the same clean power distribution, separate from lighting dimmers and motors. Keep audio multicores away from power cables, crossing them at right angles where they must cross. Put playback computers and RF racks on an uninterruptible power supply.

Miking the drum kit

A drum kit is usually the largest single group of inputs on the stage, often ten to sixteen channels: a microphone inside the kick drum and sometimes one outside, top and bottom snare, one per tom, hi-hat, overheads, and often a ride. Common choices include a Shure Beta 91A or Audix D6 for the kick, a Shure SM57 on the snare, Sennheiser MD421s or e904s on the toms, and a pair of small condensers overhead.

The kit is served by its own sub-snake on the riser, with every microphone clip checked for tightness, because a drummer hits everything and anything loose will move by the second song. Keep microphones clear of the drummer's sticks, and cables clear of the pedals.

Guitar and bass amplifiers

Guitar amplifiers are usually miked close on one speaker with a dynamic microphone such as a Shure SM57 or Sennheiser e906, placed just off the centre of the speaker cone for a slightly less bright sound. Some guitarists use amp modellers such as a Kemper or Fractal unit instead, which arrive by DI with no amplifier on stage at all.

Bass is usually taken both by DI, for a clean and consistent low end, and by a microphone on the cabinet for character. The two must be checked for polarity together, because a DI and a microphone a little way from the speaker can partly cancel.

DI boxes, by type

Passive for active sources; active for passive sources.

Curing hum safely

Break the loop in the audio path. Never touch the mains earth.

How to do it

1. Walk the backline with the band's technician and agree every output you are taking.
2. Choose passive or active DIs to suit each source.
3. Confirm the playback rig's redundancy switcher and route the click correctly.
4. Power all audio backline from the clean audio distribution.
5. Line check every source; cure any hum in the audio path only.

What goes wrong

Practice it

With a keyboard rig and a bass.

Running IEMs & Stage on a Show

Once doors open, the stage technician's job becomes readiness: batteries fresh, spares within reach, meters watched, and a clear path to any performer who needs something. Most of what happens during the show was decided by how well the afternoon went.

On the night, keep every performer's mix right and the stage working.

Supporting performers' monitoring live

During the show the stage technician is the monitor engineer's hands on stage. When a performer's pack fails, the technician brings the spare. When a wedge is kicked off its aim, the technician puts it back. When an earpiece cable goes intermittent, the technician swaps it between songs.

That needs a position with a view of the stage and of the monitor engineer, a comms channel or an agreed set of signals with the monitor desk, and every spare laid out in the same place every night so it can be found without light.

Keeping the complex stage working

On a large stage something is always moving: a guitarist changing instruments, a keyboard stand being struck for a solo section, a guest arriving. The stage technician tracks the running order, knows what changes when, and pre-sets anything that can be pre-set.

Patrol between songs. Look at every cable in the performers' paths, every microphone clip, every DI, every pack worn on a belt. Most stage faults give a warning -- a cable stretched across a walkway, a microphone stand slowly drooping -- and a technician who patrols fixes them before they become faults.

Batteries and spare stock

Batteries are the commonest cause of wireless failure on stage, and they are completely preventable. Every microphone and every pack starts every show with fresh cells or a full charge, regardless of what the meter says, and the change is logged.

Rechargeable systems, such as Shure's SB900 packs, make this easier and more reliable, but only if the charging is disciplined: packs go on charge the moment the show ends, and a charged set is always ready. Spare stock -- packs, microphones, cables, earpieces, DIs -- lives in a labelled case at the side of the stage.

Changeovers and rolling risers

At a festival, or on a show with a support act, the stage changes over in minutes. The technique that makes this possible is preparation: the incoming band's drum kit and keyboards set up on rolling risers in the wings, already miked, already cabled to labelled sub-snakes, ready to roll into place and connect with a handful of multicores.

Wireless is coordinated for every act in advance, with the next act's microphones and packs ready and tested. The line check after a changeover is fast because everything was checked on the riser before it rolled on.

Show-day stage readiness

The show is decided in the afternoon.

How to do it

1. Replace or recharge every battery, and log it.
2. Lay out spares in their fixed place side-stage.
3. Agree signals or comms with the monitor engineer.
4. Patrol cables, clips, stands and packs between songs.
5. Pre-set every change on the running order.
6. Put everything on charge the moment the show ends.

What goes wrong

Practice it

At the next show you work on stage.

What Goes Wrong on Stage

Stage faults have a small number of causes, and a method finds them fast. The method is the same as for any signal: follow the path, test each link, and fix the first one that fails.

Hum and buzz

A steady hum at mains frequency or its harmonics is almost always a ground loop. Find which source it is on by muting channels one at a time, then break the loop at that source's DI or with an isolation transformer. A buzz with a harsher, more rattling character is often interference from lighting dimmers or LED drivers, cured by moving the cable or the source away from them.

Dead channels and crackles

A channel with no signal is a path to walk: the source, the cable, the sub-snake, the stage box input, the network, the console patch. Swap the cable first -- it is the commonest failure and the fastest test. A crackle that comes and goes as something is touched is almost always a failing cable or connector.

Phantom power is the other frequent cause. A condenser microphone or active DI with no phantom power produces nothing; a passive ribbon microphone can be damaged by a faulty cable carrying it.

Wireless dropouts

A wireless microphone or in-ear pack that cuts in and out is a radio problem. Look at the receiver's signal meter: a weak signal points to antenna placement or a performer moving out of coverage; a strong signal with noise points to interference, and the answer is the backup frequency from the coordination plan.

A battery near the end of its life can also cause dropouts before it fails completely, which is one more reason to change every show.

Phantom power faults

Condenser microphones and active DI boxes need phantom power, sent up the microphone cable from the stage box. With it off they are silent; with a faulty cable they may crackle or cut out. On a networked stage, phantom is switched from the console, so a channel that is silent on stage may simply have phantom switched off at a desk three hundred feet away.

Phantom can also cause faults. Hot-plugging a cable with phantom on produces a loud pop that can damage loudspeakers and ears, so mute the channel before connecting. Some older ribbon microphones can be damaged by phantom through a faulty cable, so check what is on a channel before switching it on.

Network and stage box faults

When a whole block of inputs disappears at once, the fault is not in the microphones. It is the stage box, its power, or its network link. Check the stage box's status lights and the network link lights first; on a redundant system the console will usually report which path failed.

Clock faults on a digital system produce clicks and dropouts across many channels at once. Every device on a digital audio network follows one clock leader; if a device loses the clock, or two devices both try to lead, audio breaks up everywhere at once. The symptom to recognise is many channels, same moment, same kind of click -- and the first check is the clock status on the console and the network devices, before a single microphone is touched.

Tagging out and the repair log

The most important habit after finding a faulty cable, microphone or pack is to make sure it never comes back on stage. Tag it with a strip of coloured tape and a note of the fault, put it in a separate case, and log it. A faulty cable coiled back into stock will fail again on the next show, at a worse moment.

The repair log -- what failed, when, and what the fault was -- also reveals patterns: a batch of cables failing at the same connector, a pack that keeps dropping out, a stage box input that crackles. Those patterns are fixed once, properly, instead of being chased every night.

Stage faults and their usual causes

Follow the path; fix the first link that fails.

How to do it

1. Identify the channel or system affected.
2. Decide which kind of fault it is -- hum, dead, crackle or dropout.
3. Walk the path from the source towards the console.
4. Swap the cheapest, commonest part first -- usually the cable.
5. Fix the first link that fails, and label any faulty item out of service.

What goes wrong

Practice it

On a stage you can experiment on safely.

Mastering Stage Audio

The stage technician is rarely noticed on a good night, and that is the measure of the job. This chapter sets out the complete skill set and the route through a career built on it.

Master IEMs and complex stages, and you can run audio for the biggest shows.

The complete stage-audio professional

A complete stage-audio professional can follow the in-ear path from console to ear and find any fault in it. They can set up transmitters, packs, combiners and antennas properly, fit earpieces, and hand over a performer's mix safely. They understand the radio spectrum, coordinate thirty channels as one system, and keep a backup for every critical one.

They can manage ninety inputs with a dated patch sheet, network stage boxes and isolated splits; connect a band's backline with the right DIs and a redundant playback rig; cure hum safely; and run a stage through a show and a changeover with fresh batteries and spares always within reach.

Growing in stage and monitor work

Stage work is where most monitor engineers and many system technicians begin. The path usually runs from stagehand to stage technician or A2, then to monitor technician or RF technician, and from there to monitor engineer, RF coordinator or systems specialist.

What carries people along it is reliability, fluency with the standard equipment, and the trust of the engineers and performers they support. Manufacturer training -- Shure and Sennheiser both run wireless courses -- is worth taking, and learning Wireless Workbench properly is one of the most useful single skills a stage technician can add.

Practical sign-off

Advanced stage audio is built on bigger shows. The learner sets up IEM systems, builds and dials in personal mixes at safe levels, manages a complex stage and RF, and supports performers' monitoring live. A mentor signs off when the learner can run advanced stage audio on a demanding show.

• Set up an IEM system and traced its signal path
• Built and dialed in personal IEM mixes at safe levels
• Managed a complex input list, splits, and RF coordination
• Supported performers' monitoring responsively through a show

Working with the people around the stage

The stage technician sits between several people who all depend on them: the monitor engineer, who needs every mix to arrive; the front-of-house engineer, who needs every input clean; the RF coordinator, who needs every system on its assigned frequency; and the backline technicians, who know the band's equipment better than anyone.

The habit that makes the job work is telling people things before they need to ask: "the guitarist changed amps, input 22 is different today"; "the bass DI is now active, phantom on 18"; "vocal pack two is on its backup frequency". A stage technician who communicates like that makes every engineer's show easier, and gets booked again.

The stage career path

Learned on stages, carried forward by reliability.

How to do it

1. Learn the in-ear signal path until you can walk it blindfold.
2. Learn Wireless Workbench or WSM properly.
3. Take a manufacturer's wireless course.
4. Keep your own patch sheets and battery logs from every show.
5. Ask monitor engineers what they need from the stage, and provide it.

What goes wrong

Practice it

Over the next month.

Glossary

What the gear actually looks like

Every device named in this book, in one place. Recognition is the whole point of Chapter 4 — use this page to attach a picture to each name before you meet it on a dock at six in the morning.

Audio

Dynamic microphone

Condenser microphone

Wireless handheld

Radio rack

Mixing console

Stage box / snake

Power amplifier

Main loudspeaker

Subwoofer

Stage monitor wedge

In-ear monitors

DI box

Video

Camera

Video switcher

Scaler / processor

Projector

LED wall panel

Confidence monitor

Lighting & control

Conventional fixture

Moving-head fixture

Lighting console

Dimmer

Show controller

Media server

Networking & infrastructure

Network switch

Patch bay

Equipment rack

Power distribution

Cable tester

A properly coiled cable

Connectors, close up

XLR

TRS / TS ¼-inch

SDI on BNC

HDMI

Cat5e / Cat6 (RJ45)

Fiber optic

DMX (5-pin XLR)

AC power — not signal