AV glossary

Video and screens first, because that is what most quotes argue about. Audio, lighting, staging, rigging and power follow.

• A-weighting (dBA) The filter almost every noise ordinance is written in. It takes the low end off the reading, so a subwoofer-heavy show measures quieter than it feels.
• ADA ramp The accessible route on to a stage — a slope no steeper than one in twelve, so a two-foot stage needs about twenty-four feet of ramp before landings.
• Backdrop The surface behind the stage — fabric, printed, hard scenic or an LED wall — and the decision that sets what the lighting and the cameras can do.
• Box truss The square aluminium lattice everything hangs from — rated for a load in addition to its own weight, and only as strong as the span it is asked to cross.
• Bridle Two legs run from separate attachments to a common point, used when the hang position does not line up with a beam — geometry that multiplies tension.
• Cam-Lok (camlock) The single-pole connector feeder cable lands on — one conductor per connector, colour-coded by convention rather than by code, and connected ground first.
• Chain motor The electric hoist that lifts truss and scenery on a loop of chain — rated by capacity, and not by itself a licence to leave a load hanging over people.
• Colour temperature How warm or cool a white light is, in kelvin — the number that decides whether skin tones hold up on camera, and the one a cheap fixture flatters.
• Company switch The venue’s connection point for temporary power — a protected tap installed so a production can land feeder without touching the building’s panels.
• Confidence monitor A screen facing the stage rather than the audience, showing the presenter their own slides so they never have to turn around.
• Cyclorama (cyc) A large, smooth, pale cloth lit as a coloured sky behind everything else — the simplest way to give a stage depth, and unforgiving of creases.
• Dance floor A hard, level surface laid over carpet — straightforward to rent, and routinely undersized and set down on a floor that is not flat.
• Dead hang A straight vertical suspension from a single point — the simplest and cheapest way to hang anything, and the reason rig positions are negotiable.
• Delay tower A loudspeaker position partway down a field or a long room, electronically delayed so its sound arrives just after the main system’s rather than before it.
• DI box The small box that turns an instrument or laptop output into a balanced signal a long cable can carry, and stops a hundred-foot run from humming.
• DMX The control language every lighting fixture speaks — five hundred and twelve channels to a universe, and a terminator at the end of the line.
• Ellipsoidal (profile) The fixture that can be cut to a shape, hold a hard edge and project a pattern — optically a slide projector, and the one that stops light where you want.
• Fast-fold screen A large projection screen on a folding frame that assembles on site, dressed with skirting and available for front or rear projection.
• Feeder cable The heavy single-conductor cable between the power source and the distro — one conductor per jacket, run in sets, and governed on site by where people walk.
• Flame resistance certificate The document a fire marshal asks for about the fabric in your room — a test method rather than a rating, and one that has to name the actual material.
• Followspot A manually operated spotlight that keeps a pool of light on somebody moving — still the only reliable way, and a position built into the rig up front.
• Frequency coordination Choosing an operating frequency for every wireless device on site so none of them, in combination, lands on another. It decides whether the mics hold.
• Fresnel A soft-edged wash fixture with a stepped lens, adjustable from spot to flood by moving the lamp, and shaped at the edges with barn doors rather than shutters.
• Front of house (FOH) The mix position out in the room where the engineer sits, and the audio the audience actually hears. Not a department, and not spare seating.
• Gain structure Setting the level at each stage of the signal chain so the system runs above its noise and below its ceiling. What is wrong when a mix sounds brittle.
• General session (plenary) General session production is building and running the one room a conference puts its whole audience in at once — the hall everything else is timed around.
• Generator (event) Portable power for a site that has none — specified by the load it will actually carry, and hurt more by running too light than by running too heavy.
• GFCI Protection that cuts power when current leaks to ground — required on ordinary outlets the public can reach outdoors, and not permitted on exit lighting.
• Gobo A cut or etched template dropped into a fixture so it projects a shape — a window, a texture, a logo — sized by what fits the gate, not by the picture.
• Ground stack Loudspeakers stacked on the deck or on the ground rather than flown — the usual configuration outdoors, where there is often nothing overhead to hang from.
• Ground support Towers standing on the floor to hold a rig up, used when the building has no points to hang from or there is no building at all. Engineering, not kit.
• Grounding and bonding Tying metal together so a fault has a path back to its source — two different jobs under one name, and the step missed when a stage is fed from two supplies.
• Guardrail The barrier along an open edge — required by code above thirty inches, built at forty-two, with a performance-area exception that is routinely misread.
• Haze A fine, even suspension in the air that makes light beams visible — not fog, not smoke, and the thing on a lighting plot most likely to trip a fire alarm.
• Headset microphone A microphone on a thin boom worn over the ear, an inch or two from the mouth — worth roughly ten decibels of extra level before the system rings.
• House rigger The venue’s own rigging crew, who in most convention centres and arenas are the only people allowed to attach anything to the building. A schedule item.
• IMAG (image magnification) Live camera feed of whoever is on stage, put up on the screens so the back of the room can see a face instead of a distant figure.
• In-ear monitors (IEM) A personal monitor mix sent to a performer’s earpieces by radio — quieter stage, better mix, and more frequencies to coordinate with the microphones.
• Lavalier microphone The small clip-on microphone worn on a lapel — invisible on camera, and the one whose sound is decided almost entirely by where it is placed.
• Lectern The stand a speaker reads from, which is not a podium however often the words are swapped, and a microphone position before it is ever furniture.
• LED panel (cabinet) The individual module an LED wall is built from — typically 500mm square, hung or stacked in a grid, and the unit everything about a wall is counted in.
• LED wall A screen built from modular LED panels bolted together, bright enough to read in daylight and sized to the space rather than to a projector lens.
• Lighting console The desk that holds the patch, the looks and the running order — and the reason a show can be rebuilt in ten minutes when a speaker is moved up the programme.
• Line array A column of loudspeakers hung in a curve so the sound reaches the back row without flattening the front. The standard answer for a deep room or field.
• Load calculation Working out what the rig actually draws before anybody orders a service — where the common mistake is treating a 20-amp circuit as 20 amps.
• Load-in Getting the show into the building — decided by the dock, the door, the lift and the route, none of which appear on a floor plan.
• Masking The drape that defines what the audience cannot see — legs at the sides, a border across the top, and the line between a finished stage and a visible crew.
• Media server A purpose-built playback machine that drives screens reliably — the reason a show does not depend on somebody’s laptop not going to sleep.
• Monitor wedge The angled loudspeaker on the deck pointed back at a performer — the oldest way to hear yourself, and what sets the ceiling on microphone level.
• Moving head A fixture that pans, tilts and changes colour, beam and pattern on command — sold in three distinct flavours that get confused when a rig is specified.
• PAR fixture The simplest instrument in the rig — an oval pool of hard, bright light with its beam spread built into the lamp rather than adjusted at the fixture.
• Pipe and drape Weighted bases, uprights and crossbars carrying fabric panels — the fastest way to build a wall, and the thing most often ordered short.
• Pixel pitch The distance in millimetres between the centres of two adjacent LEDs — the number that decides how close your audience can sit, not how good the screen is.
• Point load The force delivered into one attachment — the number a building is rated against, and the reason total rig weight is the wrong thing to quote a venue.
• Power distro The portable box that takes one large feed and breaks it into protected circuits, sitting between a building’s power and every piece of gear on the show.
• Projection mapping Projecting onto something that is not a flat white screen — a building, a set piece, a staircase — with the image built to fit that exact surface.
• Proscenium The frame a stage is viewed through — a wall with an opening in it, which decides what the audience can see and gives everything else somewhere to hide.
• Rear projection Projecting from behind the screen instead of in front of it, so nobody walks through the beam and no presenter is ever lit up by the projector.
• Rigging plot The drawing that says what hangs where, how heavy each point is and how high it trims — submitted to the venue weeks ahead, not produced on the day.
• Rigging point One place where a load is attached to the building, counted and rated individually, because the building cares where the weight is rather than how much.
• Riser A small raised platform for a specific thing — a drum kit, a camera, a choir, a panel — and almost always the piece that gets left off the drawing.
• Scenic flat A rigid built panel — the hard version of a backdrop, which takes real finishes and real shadow, and arrives on a truck with its own build time.
• Scrim An open-weave fabric that reads solid lit from the front and transparent lit from behind — the oldest reveal in the business, and it needs only light.
• Shackle The steel link that connects a sling to a point or a motor — rated, stamped, and ruined by being loaded from the side or closed with the wrong pin.
• Shore power Using the building’s own supply instead of generating your own — quieter, cheaper and cleaner when it exists in the quantity the show actually needs.
• Sightlines What each seat can actually see — the thing that decides stage height, screen height and where a camera platform may stand, and the thing a flat floor ruins.
• Socapex A 19-pin multicable carrying six 20-amp circuits in one jacket — six hots, six neutrals, six grounds, and one pin left over.
• Soft goods The collective name for every piece of fabric in a production — drapes, legs, borders, skirts, cycs and backdrops — a category that lives on its paperwork.
• Span set (round sling) A continuous loop of polyester in a protective jacket, used to wrap a beam or a truss — rated for how it is used, not just for what it is.
• Stage deck The modular platform a stage is built from — four feet by eight in most of the country, with the height set by the legs rather than by the deck.
• Stage directions Stage left, stage right, upstage and downstage — all four given from the performer’s point of view, which is why half the room points the wrong way.
• Stage pin connector The flat two-pin-and-ground plug on theatrical circuits — built for heat and repeated use, and not interchangeable with the household plug it sits beside.
• Stage skirt The pleated fabric that closes the gap between the deck and the floor — the cheapest thing on the stage and the first thing a photograph notices.
• Stage stairs The steps up to a stage — where the trap is that a convenient riser height is also an illegal one.
• Stage wash The even, flattering light a person stands in to be seen — the least glamorous part of a lighting plot and the first thing a camera exposes as missing.
• Step and repeat The logo wall people are photographed against — built on an eight-foot module, and ruined by gloss, clutter and a straight-on flash.
• Subwoofer The cabinet that carries the bottom two octaves, and the one whose placement rather than quantity decides whether a room has even bass or dead spots.
• Teleprompter Scrolling script reflected onto angled glass so a speaker reads while looking straight ahead — at the audience, or down the barrel of a camera.
• Three-phase power The service nearly every event runs on: three live conductors and a neutral, giving 120 volts to neutral and 208 between phases, which is not 240.
• Thrust stage A stage that extends into the audience with seating on three sides — intimate, and a complete rewrite of where lighting, loudspeakers and cameras can go.
• Uplighting Small fixtures set on the floor and aimed up a wall or column to put colour into a room — the cheapest thing that changes how a ballroom feels.
• Video switcher The device that decides which source the screens are showing at any given second, and the person operating it is as much of the specification as the box.
• Wireless microphone A microphone with a radio transmitter instead of a cable, legal in a narrower slice of spectrum than most people assume, and not bought by channel count.
• Working load limit (WLL) The most a piece of rigging hardware may be asked to carry — typically a fifth of what would break it, and halved again for anything over people.