Subwoofer in the context of Keyboard amplifier

A movie theater (American English) or cinema (Commonwealth English), also known as a movie house, cinema hall, picture house, picture theater, the movies, the pictures, the big screen (colloquialism), or simply theater, is a business that contains auditoriums for viewing films for public entertainment. Most are commercial operations catering to the general public, who attend by purchasing tickets.

The film is projected with a movie projector onto a large projection screen at the front of the auditorium while the dialogue, sounds and music are played through a number of wall-mounted speakers. Since the 1970s, subwoofers have been used for low-pitched sounds. Since the 2010s, the majority of movie theaters have been equipped for digital cinema projection, removing the need to create and transport a physical film print on a heavy reel.

A bass reflex system (also known as a ported, vented box or reflex port) is a type of loudspeaker enclosure that uses a port (hole) or vent cut into the cabinet and a section of tubing or pipe affixed to the port. This port enables the sound from the rear side of the diaphragm to increase the efficiency of the system at low frequencies as compared to a typical sealed- or closed-box loudspeaker or an infinite baffle mounting.

A reflex port is the distinctive feature of this popular enclosure type. The design approach enhances the reproduction of the lowest frequencies generated by the woofer or subwoofer. The port generally consists of one or more tubes or pipes mounted in the front (baffle) or rear face of the enclosure. Depending on the exact relationship between driver parameters, the enclosure volume (and filling if any), and the tube cross-section and length, the efficiency can be substantially improved over the performance of a similarly sized sealed-box enclosure.

An electrodynamic speaker driver, often called simply a speaker driver when the type is implicit, is an individual transducer that converts an electrical audio signal to sound waves. While the term is sometimes used interchangeably with the term speaker (loudspeaker), it is usually applied to specialized transducers that reproduce only a portion of the audible frequency range, or to the one or more drivers within a loudspeaker cabinet (or simply "speaker".). For high fidelity reproduction of sound, multiple loudspeakers are often mounted in the same enclosure, each reproducing a different part of the audible frequency range. In this case the individual speakers are referred to as drivers and the entire unit is called a loudspeaker. Drivers made for reproducing high audio frequencies are called tweeters, those for middle frequencies are called mid-range drivers (much less commonly called squawkers), and those for low frequencies are called woofers, while those for very low bass range are subwoofers. Less common types of drivers are supertweeters and rotary woofers.

The electroacoustic mechanism most widely used in speakers to convert the electric current to sound waves is the dynamic or electrodynamic driver, invented in 1925 by Edward W. Kellogg and Chester W. Rice, which creates sound with a coil of wire called a voice coil suspended between the poles of a magnet. There are others that are far less widely used: electrostatic drivers, piezoelectric drivers, planar magnetic drivers, Heil air motion drivers, and ionic drivers, among other speaker designs.

A loudspeaker enclosure or loudspeaker cabinet is an enclosure (often rectangular box-shaped) in which speaker drivers (e.g., woofers and tweeters) and associated electronic hardware, such as crossover circuits and, in some cases, power amplifiers, are mounted. Enclosures may range in design from simple, homemade DIY rectangular particleboard boxes to very complex, expensive computer-designed hi-fi cabinets that incorporate composite materials, internal baffles, horns, bass reflex ports and acoustic insulation. Loudspeaker enclosures range in size from small "bookshelf" speaker cabinets with 4-inch (10 cm) woofers and small tweeters designed for listening to music with a hi-fi system in a private home to huge, heavy subwoofer enclosures with multiple 18-inch (46 cm) or even 21-inch (53 cm) speakers in huge enclosures which are designed for use in stadium concert sound reinforcement systems for rock music concerts.

The primary role of an enclosure is to prevent sound waves generated by the rearward-facing surface of the diaphragm of an open speaker driver interacting with sound waves generated at the front of the speaker driver. Because the forward- and rearward-generated sounds are out of phase with each other, any interaction between the two in the listening space creates a distortion of the original signal as it was intended to be reproduced. As such, a loudspeaker cannot be used without installing it in a baffle of some type, such as a closed box, vented box, open baffle, or a wall or ceiling (infinite baffle).

Audio crossovers are a type of electronic filter circuitry that splits an audio signal into two or more frequency ranges, so that the signals can be sent to loudspeaker drivers that are designed to operate within different frequency ranges. The crossover filters can be either active or passive. They are often described as two-way or three-way, which indicate, respectively, that the crossover splits a given signal into two frequency ranges or three frequency ranges. Crossovers are used in loudspeaker cabinets, power amplifiers in consumer electronics (hi-fi, home cinema sound and car audio) and pro audio and musical instrument amplifier products. For the latter two markets, crossovers are used in bass amplifiers, keyboard amplifiers, bass and keyboard speaker enclosures and sound reinforcement system equipment (PA speakers, monitor speakers, subwoofer systems, etc.).

Crossovers are used because most individual loudspeaker drivers are incapable of covering the entire audio spectrum from low frequencies to high frequencies with acceptable relative volume and absence of distortion. Most hi-fi speaker systems and sound reinforcement system speaker cabinets use a combination of multiple loudspeaker drivers, each catering to a different frequency band. A standard simple example is in hi-fi and PA system cabinets that contain a woofer for low and mid frequencies and a tweeter for high frequencies. Since a sound signal source, be it recorded music from a CD player or a live band's mix from an audio console, has all of the low, mid and high frequencies combined, a crossover circuit is used to split the audio signal into separate frequency bands that can be separately routed to loudspeakers, tweeters or horns optimized for those frequency bands.

Studio monitors are loudspeakers in speaker enclosures specifically designed for professional audio production applications, such as recording studios, filmmaking, television studios, radio studios and project or home studios, where accurate audio reproduction is crucial. Among audio engineers, the term monitor implies that the speaker is designed to produce relatively flat (linear) phase and frequency responses. In other words, it exhibits minimal emphasis or de-emphasis of particular frequencies, the loudspeaker gives an accurate reproduction of the tonal qualities of the source audio ("uncolored" and "transparent" are synonyms), and there will be no relative phase shift of particular frequencies—meaning no distortion in sound-stage perspective for stereo recordings. Beyond stereo sound-stage requirements, a linear phase response helps impulse response remain true to source without encountering "smearing". An unqualified reference to a monitor often refers to a near-field (compact or close-field) design. This is a speaker small enough to sit on a stand or desk in proximity to the listener, so that most of the sound that the listener hears is coming directly from the speaker, rather than reflecting off walls and ceilings (and thus picking up coloration and reverberation from the room). Monitor speakers may include more than one type of driver (e.g., a tweeter and a woofer) or, for monitoring low-frequency sounds, such as bass drum, additional subwoofer cabinets may be used.

There are studio monitors designed for mid-field or far-field use as well. These are larger monitors with approximately 12 inch or larger woofers, suited to the bigger studio environment. They extend the width of the sweet spot, allowing "accurate stereo imaging for multiple persons". They tend to be used in film scoring environments, where simulation of larger sized areas like theaters is important.

A rave (from the verb: to rave) is a dance party at a warehouse, club, or other public or private venue, typically featuring performances by DJs playing electronic dance music. The style is most associated with the early 1990s dance music scene when DJs played at illegal events in musical styles dominated by electronic dance music from a wide range of sub-genres, including drum and bass, dubstep, trap, break, happy hardcore, trance, techno, hardcore, house, and alternative dance. Occasionally live musicians have been known to perform at raves, in addition to other types of performance artists such as go-go dancers and fire dancers. The music is amplified with a large, powerful sound reinforcement system, typically with large subwoofers to produce a deep bass sound. The music is often accompanied by laser light shows, projected coloured images, visual effects and fog machines.

Fuelled by the emerging dance scene, and spearheaded by acid house music and underground bands such as The Prodigy, many of the "acid house" parties were held in squats during the late 1980s. Well known locations such as the "Dole House" (Peckham), the abandoned bus station and the squatted children's home in Camberwell known as Groove Park had crowds of over a thousand. Full Moon parties were organised at Groove Park by Pete Marland (who went on to start the dance scene in Western Ireland in the early 1990s) and multiple events went on for over a year as an Art Collective sanctioned by locals. The Times' first colour supplement carried an article about the dance scene at Groove Park, though some of the organisers did not want to be photographed. While some raves may be small parties held at nightclubs or private homes, some others have grown to immense size, such as the large festivals and events featuring multiple DJs and dance areas (e.g., the Castlemorton Common Festival in 1992).

A soundbar, sound bar or media bar is a type of loudspeaker that projects audio from a wide enclosure. It is much wider than it is tall, partly for acoustic reasons, and partly so it can be mounted above or below a display device (e.g. above a computer monitor or under a home theater or television screen). In a soundbar, multiple speakers are placed in a single cabinet, which helps to create stereo sound and surround sound effect. A separate subwoofer is typically included with, or may be used to supplement, a soundbar.

Computer speakers, or multimedia speakers, are speakers marketed for use with computers, although usually capable of other audio uses, e.g. for a shelf stereo or television. Most such speakers have an internal amplifier and consequently require a power source, which may be by a mains power supply often via an AC adapter, batteries, or a USB port. The signal input connector is often an analog 3.5 mm jack plug (usually color-coded lime green per the PC 99 standard); RCA connectors are sometimes used, and a USB port or Bluetooth antenna may supply a digital signal to an onboard DAC (some of which work only on computers with an appropriate device driver). Battery-powered wireless speakers require no cables at all. Most computers have speakers of low power and quality built in; when external speakers are connected they disable the built-in speakers by default. Altec Lansing claims to have created the computer speaker market in 1990.

Computer speakers range widely in quality and in price. Computer speakers packaged with computer systems are typically small, plastic, and have mediocre sound quality. Some computer speakers have equalization features such as bass and treble controls. More sophisticated computer speakers can have a subwoofer unit to enhance bass output. The larger subwoofer enclosure usually contains the amplifiers for the subwoofer and the left and right speakers.

A bass amplifier (also abbreviated to bass amp) is a musical instrument electronic device that uses electrical power to make lower-pitched instruments such as the bass guitar or double bass loud enough to be heard by the performers and audience. Bass amps typically consist of a preamplifier, tone controls, a power amplifier and one or more loudspeakers ("drivers") in a cabinet.

While bass amps share many features with the guitar amplifiers used for electric guitar, they are distinct from other types of amplification systems, due to the particular challenges associated with low-frequency sound reproduction. This distinction affects the design of the loudspeakers, the size and design of the speaker cabinet and the design of the preamplifier and amplifier. Speaker cabinets for bass amps usually incorporate larger loudspeakers (e.g., 15 inches (380 mm) speakers are more common for bass than for electric guitar amps) or more speakers and larger cabinet sizes than those used for the amplification of other instruments. The loudspeakers themselves must also be sturdier to handle the higher power levels and they must be capable of reproducing very low pitches at high sound pressure levels.

A rotary woofer is a subwoofer-style loudspeaker which reproduces very-low-frequency content by using a conventional speaker voice coil's motion to change the pitch (angle) of the blades of an impeller rotating at a constant speed. The pitch of the fan blades is controlled by the audio signal presented to the voice coil, and is able to swing both positive and negative, with respect to a zero-pitch blade position. Since the audio amplifier only changes the pitch of the blades, it takes much less power for a given sound level to drive a rotary woofer than a conventional subwoofer, which uses a moving electromagnet (voice coil) placed within the field of a stationary permanent magnet to move a diaphragm to displace air. Rotary woofers excel at producing sounds below 20 Hz, below the normal hearing range; when installed in a wall of a sealed room, they can produce arbitrarily low frequencies, down to a static pressure differential, by simply compressing or decompressing the air in the sealed room.

A line array is a loudspeaker system that is made up of a number of usually identical loudspeaker elements mounted in a line and fed in phase, to create a near-line source of sound. The distance between adjacent drivers is close enough that they constructively interfere with each other to send sound waves farther than traditional horn-loaded loudspeakers, and with a more evenly distributed sound output pattern.

Line arrays can be oriented in any direction, but their primary use in public address is in vertical arrays which provide a very narrow vertical output pattern useful for focusing sound at audiences without wasting output energy on ceilings or empty air above the audience. A vertical line array displays a normally wide horizontal pattern useful for supplying sound to the majority of a concert audience. By contrast, horizontal line arrays have a very narrow output pattern horizontally but a tall pattern vertically. A row of subwoofers along the front edge of a concert stage can behave as a horizontal line array unless the signal supplied to them is adjusted (delayed, polarized, equalized) to shape the pattern otherwise. Loudspeakers can be designed to be arrayed horizontally without behaving as a horizontal line source.