Glossary of Terms - E

A glossary of terms covering lighting, audio, vision and staging in the event and theatrical industry.

There can be a number of meanings for some terms which can vary from country to country and manufacturer to manufacturer. Information within this guide is indicative and every situation can require a different approach and solution. All care has been taken, however, Image Group NZ accepts no responsibility for inaccuracies. If you have any suggestions, comments or queries regarding this list please contact us.

E

E.R.S.
(ERS) Ellipsoidal Reflector Spotlight (US)

EARTH SPIKE
Copper rod inserted into the ground to maintain earth continuity (especially when using generators etc.)

EARTHING
Electrical safety requirement that metal parts of electrical equipment are connected to a common earth or ground point so that in the event of a fault, excess current can be carried away, causing the fuse to blow. Known in the USA as Ground.

ECHO
A wave which has been reflected or otherwise returned with sufficient magnitude and delay to be perceived as a distinct wave, separate from the original wave. A delay in sound of more than 50 milliseconds resulting in a distinct repeat or number of repeats of the original sound.

ECHO CANCELLATION
A technique used in high-speed modems and voice circuits to isolate and filter out unwanted signal energy caused by echoes from the main transmitted signal.

EFFECTS PROJECTOR
Lantern used to project the image from a rotating glass effects disc. Used with an objective lens to produce the desired size of image. Commonly used discs are clouds, flames and rain.

EFFECTS, LIGHTING

    Animation Disc: A slotted or perforated metal disc which rotates in front of a lantern to provide "movement" in the light. Most effective when used in front of a profile carrying a gobo.
    Effect Disc: A painted glass disc rotating in front of an effects projector with an objective lens to focus the image (eg lames, Rain, Snow).
    Flicker Flame: Irregularly slotted rotating metal disc through which light is shone onto a prism-type piece of glass which scatters the beam of light and adds the "dancing" effect of firelight to a scene.
    Gobo Rotator: Motorised device inserted into the gate of a profile lantern that can be remotely controlled to rotate a gobo, usually with variable speed and direction.
    KK Wheel: Slotted metal disc which rotates in front of a lantern to break up the light and provide movement. (Flicker Wheel)
    Lightning: Created through the use of either strobe sources or photoflood lamps.
    Tubular Wave Ripple: Horizontal linear lamp around which a slotted cylinder is rotated providing a rising light (as reflected from water onto the side of a ship).
    See also EFFECTS,SOUND, PYROTECHNICS, SMOKE.

EFFICIENCY
The ratio, usually expressed as a percentage, of the useful power output to the power input of a device. The efficiency of a speaker system is the SPL the unit produces at a 1 W RMS input power level measured 1 meter from the unit. Doubling the input power raises the SPL 3 dB. Doubling the number of enclosures raises the SPL 3 dB. Doubling the input power and the number of enclosures raises the SPL 6 dB. Doubling the distance (near field) lowers the SPL 6 dB.

EGGS
Slang term used for Strand Pattern 123's, due to their shape.

ELECTRIC
LX bars are ELECTRICs bars. LX1 in the UK (first bar upstage of the proscenium arch) is FIRST ELECTRIC.

ELECTRICS
See LX.

ELECTRONICALLY BALANCED INPUT
A differentially balanced amplifier; an amplifier whose output is proportional to the difference between the voltages applied to its two inputs. Offers common mode rejection or attenuation of interference signal that was introduced electromagnetically in the signal carrying conductors.

ELEVATION

    A working drawing usually drawn to scale, showing the side view of a set or lighting rig.
    See also PLAN.

ELLIPSOIDAL
A profile lantern with an elliptical reflector. Referred to as a LEKO.

EMF
Abbreviation for Electromotive Force, or VOLTAGE.

ENCLOSURE
An acoustically designed housing or structure for a speaker.

EQUALIZATION
The act of obtaining a desired overall frequency response through the implementation of graphic equalizers or tone controls.

EQUALIZER
A device designed to compensate for an undesired amplitude-frequency characteristic of a system or speaker.

EQUITY LIGHT
See GHOST LIGHT.

ER / E.R.
Short for Ellipsoidal Reflector - type of fixed beam profile lantern common in the US. Also known as ERS / E.R.S.

ETHERNET
Computer networking protocol which is installed on many new lighting desks, to allow networking between the main desk, dimmers, and remote desks around the theatre.

EXCITER

    See ENHANCER.
    Exciter Lamp - the lamp in a film projector that shines through the optical soundtrack and enables it to be read by a light sensor.

EXCURSION
Movement of the cone of a loudspeaker or the diaphragm of a compression driver. The higher the voltage or amplitude of the signal applied, the greater the movement or excursion of the loudspeaker or diaphragm.

EXIT SIGN
Usually illuminated sign, of standard size, which should always be visible, showing an audience member and the company the nearest exit.New legislation in Europe means that the word "EXIT" has been removed from these signs to be replaced by "Running Man", known more politically correctly as "Person moving purposefully".

EXPONENTIAL HORN
A speaker designed to reproduce the high frequencies. An exponential horn has a flare rate that increases with the square of the distance from the entry to the horn throat.

EXPRESSIONISM
Theatre design and performance style which places greater value on emotion than realism. The trademark Expressionist effects were often achieved through distortion.

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