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Encyclopedia > Public address
School public address system

A public address or "PA" system is an electronic amplification system with a mixer, amplifier and loudspeakers, used to reinforce a given sound (e.g.,a person making a speech, prerecorded music, or message) and distributing the 'sound' to the general public around a building. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... The term amplifier as used in this article can mean either a circuit (or stage) using a single active device or a complete system such as a packaged audio hi-fi amplifier. ... In professional audio, a mixing console, digital mixing console, mixing desk (Brit. ... For the British rock band of the same name, see Amplifier (band). ... For the Marty Friedman album, see Loudspeaker (album) An inexpensive low fidelity 3. ...


Simple PA systems are often used in small venues such as school auditoriums, churches, and small bars. PA systems with a larger number of speakers are widely used in institutional and commercial buildings, to read announcements or declare states of emergency. Intercom systems, which are often used in schools, also have microphones in each room so that the occupants can reply to the central office. Intercom system in the Pittock Mansion An intercom is an electronic communications system within a building or group of buildings. ...


There is disagreement over when to call these audio systems Sound Reinforcement (SR) systems or PA systems. Some audio engineers distinguish between the two by technology and capability, while others distinguish by intended use (e.g., SR systems are for live music whereas PA systems are usually for reproduction of speech and recorded music in buildings and institutions). This distinction is important in some regions or markets, while in other regions or markets the terms are interchangeable.[1] A sound reinforcement system is a functional arrangement of electronic components that is designed to reinforce a live sound source. ...

Contents

Small PA systems

The simplest PA systems consist of a microphone, a modestly-powered mixer-amplifier (which incorporates a mixer and an amplifier in a single cabinet) and one or more loudspeakers. Simple PA systems of this type, often providing 50 to 200 watts of power, are often used in small venues such as school auditoriums, churches, and small bars.


In North America, PA systems are also sometimes referred to as "sound reinforcement systems" [2] or simply "sound systems." [3]In colloquial British English, a PA system installed for public address in a building is sometimes referred to as a "Tannoy" system after the company of that name. [4] British English (BrE, BE, en-GB) is the broad term used to distinguish the forms of the English language used in the United Kingdom from forms used elsewhere in the Anglophone world. ... Tannoy Ltd is a British manufacturer of loudspeakers and public-address (PA) systems. ...


Public Address systems typically consist of input sources, pre-amplifiers and/or signal routers, amplifiers, control and monitoring equipment, and loudspeakers. Input sources refer to the microphones and CD Players that provide a sound input for the system. These input sources are fed into the pre-amplifiers and signal routers that determine the zones that the 'audio signal' is fed to. The preamplified signals are then passed into the amplifiers. Depending on a countries' regulation these amplifiers will amplify the audio signals to 50V, 70V or 100V speaker line level. Control equipment monitors the amplifiers and speaker lines for faults before it reaches the loudspeakers. An amplifier is a device which changes a small movement into a larger movement. ... A loudspeaker is a device which converts an electrical signal into sound. ... A microphone with a cord A microphone, sometimes called a mic (pronounced mike), is a device that converts sound into an electrical signal. ... CD may stand for: Compact Disc Canadian Forces Decoration Cash Dispenser (at least used in Japan) CD LPMud Driver Centrum-Demokraterne (Centre Democrats of Denmark) Certificate of Deposit České Dráhy (Czech Railways) Chad (NATO country code) Chalmers Datorförening (computer club of the Chalmers University of Technology) a 1960s...


Telephone paging systems

Most modern telephone systems, such as PBX and VOIP, use a paging system that acts as a liaison between the telephone and a PA amplifier. PBX redirects here. ... IP Telephony, also called Internet telephony, is the technology that makes it possible to have a telephone conversation over the Internet or a dedicated Internet Protocol (IP) network instead of dedicated voice transmission lines. ...


In key telephone systems such as those by Nortel, Toshiba or Avaya, paging equipment is usually built into the telephone system itself, and allows announcements to be paged over the phone speakers themselves, through external speakers or through both external and internal telephone speakers. Northern Telecommunications Networks, commonly known as Nortel, is a telecommunications equipment manufacturer headquartered in Canada. ... Toshiba Corporations headquarters (Center) in Hamamatsucho, Tokyo Toshiba Corporation sales by division for year ending March 31, 2005 Toshiba Corporation ) (TYO: 6502 ) is a Japanese multinational conglomerate manufacturing company, headquartered in Tokyo, Japan. ... Avaya Inc. ...


In PBX and larger VOIP telephone systems such as those by Nortel, Cisco, Avaya or Siemens, used for larger enterprise applications, paging equipment is not built into the telephone system. Instead the system provider must provide a separate paging controller connected to a trunk port on the actual telephone system. The paging controller is accessed as either an unused directory number or unused central office line. Access to the paging system is provided through a "trunk access" code or a preprogrammed feature button on the telephone set itself. PBX redirects here. ... IP Telephony, also called Internet telephony, is the technology that makes it possible to have a telephone conversation over the Internet or a dedicated Internet Protocol (IP) network instead of dedicated voice transmission lines. ... Northern Telecommunications Networks, commonly known as Nortel, is a telecommunications equipment manufacturer headquartered in Canada. ... Cisco may refer to: Cisco Systems, a computer networking company Cisco IOS, an internet router operating system CISCO Security Private Limited, a security company in Singapore Commercial and Industrial Security Corporation, a statutory board in Singapore Abbreviation for San Francisco, California Cisco (wine) The Cisco Kid, a fictional character created... Avaya Inc. ... Siemens has the following uses: Siemens is a German family name carried by generations of the telecommunications industrialists, including Werner von Siemens, Sir William Siemens, Wilhelm von Siemens and Peter von Siemens Siemens AG is a German electrical and telecommunications company, founded as a telegraph equipment manufacturer by Werner von...


Many retailers and offices choose to use the telephone system as the sole access point for the paging system, because the equipment is already "paging system" ready. That is, the business does not have to buy a separate intercom or microphone. An additional advantage, is that each telephone can access the paging system, which makes initiating a page much more convenient than having just one microphone. Many schools and other larger institutions are no longer using the large bulky microphone PA systems and have switched to telephone system paging, as it can be accessed from many different points of the school in an emergency.


One disadvantage of telephone paging systems compared to microphone paging systems, is that the noise associated with hanging up the telephone can be heard over the speakers unless the user takes the initiative to press the "switchhook" on the telephone or if the phone is equipped, pressing the Release (RLS) button, which is most commonly found on Nortel telephone systems.


Large venue PA systems

For popular music concerts, a more powerful and more complicated PA System is used to provide live sound reproduction. In a concert setting, there are typically two complete PA systems: the "main" system and the "monitor" system. Each system consists of microphones, a mixing board, sound processing equipment, amplifiers, and speakers. There is disagreement over when to call these audio systems Sound Reinforcement (SR) systems or a Public Address (PA) systems. This distinction is important in some regions or markets, while in other regions or markets the terms are interchangeable.[5] A live sound reproduction system has two main forms: A sound reinforcement system enhances the volume of the initial sound and will be designed so that as much as possible the listener will not realise that an artificial system is being used to make it easier for them to hear... A sound reinforcement system is a functional arrangement of electronic components that is designed to reinforce a live sound source. ... School public address system A public address or PA system is an electronic amplification system with a mixer, amplifier and loudspeakers, used to reinforce a given sound (e. ...

  • The "main" system (also known as "Front of House", commonly abbreviated FOH), which provides the amplified sound for the audience, will typically use a number of powerful amplifiers driving a range of large, heavy-duty loudspeakers including low-frequency speaker cabinets called subwoofers, full-range speaker cabinets, and high-range horns. A large club may use amplifiers to provide 1000 to 2000 watts of power to the "main" speakers; an outdoor concert may use 10,000 or more watts.
  • The "monitor" system reproduces the sounds of the performance and directs them towards the onstage performers (typically using wedge-shaped monitor speaker cabinets), to help them to hear the instruments and vocals. In British English, the monitor system is referred to as the "fold back". The monitor system in a large club may use amplifiers to provide 500 to 1000 watts of power to the "monitor" speakers; at an outdoor concert, there may be several thousand watts of power going to the monitor system.

At a concert in which live sound reproduction is being used, sound engineers and technicians control the mixing boards for the "main" and "monitor" systems, adjusting the tone, levels, and overall volume of the performance. In theatre and live music venues, Front of house (or FOH) refers to areas of the building that the audience has access to, generally excluding stage and backstage areas, and including the auditorium and foyer. ...


Acoustic feedback

All PA systems have a potential for feedback, which occurs when sound from the speakers returns to the microphone and is then re-amplified and sent through the speakers again. This generally manifests itself as a sharp, sudden high-volume piercing sound which can damage the loudspeakers' high-frequency horns or tweeters - and audience members' hearing. Audio feedback (also known as the Larsen effect after the Danish scientist, Søren Larsen, who first discovered its principles) is a special kind of feedback which occurs when a sound loop exists between an audio input (for example, a microphone or guitar pickup) and an audio output (for example... A Sony tweeter. ...


Sound engineers take several steps to prevent feedback, including ensuring that microphones are not pointed towards speakers, keeping the onstage volume levels down, and lowering frequency levels where the feedback is occurring, using a graphic equalizer, parametric equalizer a combination of both devices, or a notch filter. In audio processing, equalization (EQ) is the process of modifying the frequency envelope of a sound. ... For information about computer bandwidth management, see Equalization (computing). ... A notch filter, also called a band-stop filter, sometimes a narrow band-pass filter, or T-notch filter, is an electronic filter typically used when the high frequency and the low frequency are less than 1 to 2 decades apart (that is, the high frequency is less than 10...


Recent developments

In recent years, a number of technological advances have been made to PA systems.


PA speakers

High-end PA speakers have been made lighter by using neodymium speaker magnets, and horns are often wired using protective circuitry such as light bulbs (which illuminate and absorb excess wattage) or polyswitches that protect the horn from damage in the event of feedback or a dropped microphone. These new approaches to speaker protection are more convenient than the formerly used approach of fuses, because the sound system needs to be turned off to change fuses.


Digital signal processors

Small PA systems for venues such as bars and clubs are now available with features that were formerly only available on professional-level equipment, such as digital reverb effects, graphic equalizers, and, in some models, feedback prevention circuits (which electronically sense and prevent feedback "howls" before they occur). These digital signal processing multi-effect devices offer sound engineers a huge range of sound processing options (reverb, delay, echo, compression, etc.) in a single unit. In previous decades, sound engineers typically had to transport a number of heavy "rack-mounted" cases of analog effect devices. Digital signal processing (DSP) is the study of signals in a digital representation and the processing methods of these signals. ...


Amplifiers

A number of PA companies are now making lightweight, portable speaker systems for small venues that route the low-frequency parts of the music (electric bass, bass drum, etc.) to a separately-powered subwoofer. Routing the low-frequency parts of the signal to a separate amplifier and low-frequency subwoofer can substantially improve the bass-response of the system. As well, the clarity of the overall sound reproduction can be enhanced, because low-frequency sounds take a great deal of power to amplify; with only a single amplifier for the entire sound spectrum, the power-hungry low-frequency sounds can take a disproportionate amount of the sound system's power.


Power amplifiers have also become lighter, smaller, more powerful and more efficient due to increasing use of Class D amplifiers, which offer significant weight and space savings as well as increased efficiency. Block diagram of a basic switching or PWM (Class-D) amplifier. ...


Other meanings

The term "Public Address" also may refer to any IP address that is not in RFC 1918 "Private networking" scheme and is routable on the Internet. An IP address (Internet Protocol address) is a unique address that certain electronic devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP)—in simpler terms, a computer address. ... It has been suggested that RFC 1918 be merged into this article or section. ...


Footnotes

  1. ^ Borgerson, Bruce. "Is it P.A. or SR?." Sound & Video Contractor. 1 Nov. 2003. Prism Business Media. 18 Feb. 2007 <http://svconline.com/mag/avinstall_pa_sr/index.html>.
  2. ^ An Indiana, US company offers a seminar "...for those who install, configure and calibrate sound reinforcement systems." Website is at: http://www.synaudcon.com/technicians.htm
  3. ^ For example, Rat Sound Systems Inc. calls itself a "sound system" supplier. The company supplies touring sound systems and sound systems for regional and corporate events. Website is at: http://ratsound.com/vdosc.htm
  4. ^ Compact Oxford English Dictionary "Tannoy": http://www.askoxford.com/concise_oed/tannoy?view=uk
  5. ^ Borgerson, Bruce. "Is it P.A. or SR?." Sound & Video Contractor. 1 Nov. 2003. Prism Business Media. 18 Feb. 2007 <http://svconline.com/mag/avinstall_pa_sr/index.html>.

See also

A sound reinforcement system is a functional arrangement of electronic components that is designed to reinforce a live sound source. ... An instrument amplifier is an electronic amplifier designed for use with an electric or electronic musical instrument, such as an electric guitar. ...

External links

  • History of loudspeakers and amplifiers

  Results from FactBites:
 
Public address - Wikipedia, the free encyclopedia (929 words)
A public address system, abbreviated PA system, is an electronic amplification system used as a communication system in public areas.
It is an amplification setup with an amplifier and loudspeakers, used to reinforce a given sound (e.g.,a person making a speech, prerecorded music, or a live musical performance) so that the audience can hear it clearly.
The term "Public Address" also may refer to any IP address that is not in RFC 1918 "Private networking" scheme and is routable on the Internet.
  More results at FactBites »

 
 

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