Public-address system

One Public-address system (also ELA plant (electroacoustic plant or PaPlant and/or. Pa system mentioned (Pa = Public ADDRESS - Pa for power Amplifier is not meant here), serves for to the rendition and reinforcement of language or music. It exists at least out , Mixer or substations and Amplifier and can be supplemented around further devices for treatment of signals (Signalverfremdung). Very importantly the assigned propagation delay is mentioned, "Delay"; See Praezedenz effect.

Pa public-address systems are sound systems, which are used everywhere, where high requirements are placed against the rendition quality by music, language and singing. Depending upon requirement can be differently arranged the Pa.

That means it that with high volumes the sound must be defined still clearly and clearly.

The Pa system is a subsection that Stage technology and that Audio engineering.

The task of a Pa plant is to be transferred it speaking or music information to a public. Since individual loudspeakers have different efficiencies and optimal frequency ranges, loudspeakers are bundled to systems, out Subwoofern, thus systems for deep frequency ranges under approx.. 100 cycles per second and Mittel/Hochtoenern for frequency ranges over 100 cycles per second exist.

Use of Pa loudspeakers

Small Pa systems, the z.B. for birthdays, weddings, lectures, volume and to be used, one mostly arranges other musical purposes from 1-4 Subwoofern and 2-4 medium high clay/tone loudspeakers. Large Pa systems, which are used on concerts, stage performances or in Discos and Zeltfeten, mostly arrange themselves from at least four Subwoofern and six medium high clay/tone loudspeakers. The number of loudspeakers is open in principle, so that on large concerts 40 and more loudspeaker is often used. On stages the loudspeakers are interconnected frequently to towers and hung up with flight table-ware at cross beams. This prevents the intersection of frequencies, which could affect the sound negatively.

The two loudspeaker towers at the stage sides are called left and right Pa Wing (Wing = wings).

ELA plants in airports, stations, buildings in addition, in submarines or courses find a further verwendungsgebiet. Often they serve in these verwendungsgebieten also as evacuation plants. Within these ranges special substations or MMI (one Machine) are used interfaces, in order to achieve defined goals (loudspeaker circles). Usually a connecting through logic comes into the play. A connecting through consists of a source (for example a substation) and one or more goals (loudspeaker circles). Thus for example a connecting through can be activated, in order admits to give in an airport in a waiting hall the fact that a flight been late and shown in another resounds over another connecting through admits is given that the Boarding began.

Monitors

Additionally to the Pa there is one with music meetings usually still better. The additional acoustic irradiation of the stage is particularly with concerts in large resounding or with Open-Air-festival necessarily, there those Acoustic waves, which removes from the resounding rear wall or for standing buildings is reflected, only with substantial temporal delay on that . By the stage loudspeakers the musicians receive a similar impression of the sound as the public and can so interaction coordinate.

Since the use of stage loudspeakers represents extremely difficult conditions for clay/tone technicians and musicians, partly to the employment by earphones ("in acre monitors") one changes over. Here - contrary to the stage loudspeakers - none step Feedback up, which would normally develop, if z.B. a microphone the intensified and singing of a singer spent over the monitor loudspeakers again catches. In addition the sound impression for the musicians is independent of their location on the stage. In order to keep the wiring expenditure small, the earphones are usually coupled over a radio link to the Pa system. Disadvantages of the in acre monitoring is the changed space impression for the musicians, since the sound impression does not change when movement or turn. This can lead in extreme cases to orientation difficulties.

Operated a Pa plant

Naturally such large plants cannot with a commercial to be operated, since Pa plants often apply an achievement of several thousand Watts. For this several usually become Output stages with very high achievement used, which head for usually the individual channels (right/left) and frequency ranges (deep/central/high clay/tone range) separately. The complete Pa public-address system is steered via a mixer, which is connected with the output stages. The mixer contains still further connections for z.B. CD Player or other playing devices and connections for Effect devices (Compressor, Gate, Equalizer, Enhancer, Active switchesto strengthen to screen to change), which are to possess all the tasks to improve the music and language, frequencies and to emphasize or lower the heights and depths. All of these devices are manufactured in 19-Zoll units, then into for it the planned Rack are screwed in.

Wiring of a Pa plant

The signal path catches on the one hand on the stage with the instruments (inclusive Singing) and the microphones planned for it on: Here become, usually also XLRCables, the different signals into one Steam turbine and gas turbine system box and into to the mixer a leading Multi-coreCable or - with smaller plants - directly over XLR cables in the mixer led. Ideal way XLR cables should be always symmetrical, so that possible irradiations extinguish themselves mutually. To the stage signals those become additional far mentioned above signal sources (CD bringing in etc..) attached to the mixer (usually also CinchCables); most effect devices become here over INSERTCable (-Jack plug on 2x MonoJack plug) into the signal path eingeschleift.

The merged signal arrives back at the output stages (by Multicore/XLR), which ideal-proves (due to of the Ohm's resistance the cables) in the proximity of the loudspeakers stand. These become over Speakon-, in former times often also XLRCable (to be however differently wired must than XLR Mikrofonkabel) connected with the output stages.

Modern public-address systems transfer audio digitally over networks (LAN, WAN...), whereby for example the language is digitized directly at the substation it is only converted, and before the amplifier again into similar signals. Between them the data go through a DSP or a parametric Equalizer for example.

Characteristics

A special attention is with the live-beschallung on that the system.

There they often the place change and high Sound pressures to produce, are differently conceived public-address systems must than HiFiPlants. Pa plants are to be stopped more durably and more heavily and by far more complicated than HiFi plants. With large meetings so mentioned become for the setting up Roadies begun. Those are special technicians, who are engaged the Pa plant to up and diminish.

In order to reduce in areas early reflections and response, it is important to expose to sound only the ranges in which public is. In addition become

• (usually vertically oriented) loudspeaker arrays
• (usually horizontal oriented) loudspeaker cluster
• Waveguides and/or. Horn loudspeaker
• Supporting loudspeaker over Delays headed for

begun.

Further is the maximally attainable Volume (why within the Pa range loudspeaker with higher