PA system in the context of "Turntablist"

Audio feedback (also known as acoustic feedback, howlround in the UK, or simply as feedback) is a positive feedback situation that may occur when an acoustic path exists between an audio output (for example, a loudspeaker) and its audio input (for example, a microphone or guitar pickup). In this example, a signal received by the microphone is amplified and passed out of the loudspeaker. The sound from the loudspeaker can then be received by the microphone again, amplified further, and then passed out through the loudspeaker again. The frequency of the resulting howl is determined by resonance frequencies in the microphone, amplifier, and loudspeaker, the acoustics of the room, the directional pick-up and emission patterns of the microphone and loudspeaker, and the distance between them. The principles of audio feedback were first discovered by Danish scientist Søren Absalon Larsen, hence it is also known as the Larsen effect.

Feedback is almost always considered undesirable when it occurs with a singer's or public speaker's microphone at an event using a sound reinforcement system or PA system. Audio engineers typically use directional microphones with cardioid pickup patterns and various electronic devices, such as equalizers and, since the 1990s, automatic feedback suppressors, to prevent feedback, which detracts from the audience's enjoyment of the event and may damage equipment or hearing.

An open mic or open mike (shortened from "open microphone") is a live show at a venue such as a coffeehouse, nightclub, comedy club, strip club, or pub, often taking place at night (an open mic night), in which audience members may perform on stage whether they are amateurs or professionals, often for the first time or to promote an upcoming performance. As the name suggests, performers are usually provided with a microphone plugged into a PA system so that they can be better heard by the audience.

Performers may sign up in advance for a time slot with the host, who is typically an experienced performer or the venue's manager or owner. The host may screen potential candidates for suitability for the venue and give them a time to perform during the show. Open mics are focused on performance arts such as comedy (whether it be sketch or stand-up), music (often acoustic singer-songwriters), poetry, and spoken word. It is less common for groups such as rock bands or comedy troupes to perform, mostly because of the space and logistical requirements of preparing equipment and soundchecking such groups.

Turntablism is the art of manipulating sounds and creating new music, sound effects, mixes and other creative sounds and beats, typically by using two or more turntables and a cross fader-equipped DJ mixer. The mixer is plugged into a PA system (for live events) or broadcasting equipment (if the DJ is performing on radio, TV or Internet radio) so that a wider audience can hear the turntablist's music. Turntablists typically manipulate records on a turntable by moving the record with their hand to cue the stylus to exact points on a record, and by touching or moving the platter or record to stop, slow down, speed up or, spin the record backwards, or moving the turntable platter back and forth (the popular rhythmic "scratching" effect which is a key part of hip hop music), all while using a DJ mixer's cross-fader control and the mixer's gain and equalization controls to adjust the sound and level of each turntable. Turntablists typically use two or more turntables and headphones to cue up desired start points on different records (Greasley & Prior, 2013).

Turntablists, often called DJs (or "deejays"), generally prefer direct-drive turntables over belt-driven or other types, because the belt can be stretched or damaged by "scratching" and other turntable manipulation such as slowing down a record, whereas a direct drive turntable can be stopped, slowed down, or spun backwards without damaging the electric motor. The word turntablist is claimed to be originated by Luis "DJ Disk" Quintanilla (Primus, Herbie Hancock, Invisibl Skratch Piklz). After a phone conversation with Disk, it was later popularised in 1995 by DJ Babu to describe the difference between a DJ who simply plays and mixes records and one who performs by physically manipulating the records, stylus, turntables, turntable speed controls and mixer to produce new sounds. The new term coincided with the resurgence of hip-hop DJing in the 1990s.

A music venue is any location used for a concert or musical performance. Music venues range in size and location, from a small coffeehouse for folk music shows, an outdoor bandshell or bandstand or a concert hall to an indoor sports stadium. Typically, different types of venues host different genres of music. Opera houses, bandshells, and concert halls host classical music performances, whereas public houses ("pubs"), nightclubs, and discothèques offer music in contemporary genres, such as rock, dance, country, and pop.

Music venues may be either privately or publicly funded, and may charge for admission. An example of a publicly funded music venue is a bandstand in a municipal park; such outdoor venues typically do not charge for admission. A nightclub is a privately funded venue operated as a profit-making business; venues like these typically charge an entry fee to generate a profit. Music venues do not necessarily host live acts; disc jockeys at a discothèque or nightclub play recorded music through a PA system.

A digital piano is a class of electronic keyboard or synthesizer (rompler) designed to serve primarily as an alternative to the traditional acoustic piano, both in how it feels to play and in the sound it produces. Digital pianos use either synthesized emulation or recorded samples of an acoustic piano, which are played through one or more internal loudspeakers. They also incorporate weighted keys, which recreate the feel of an acoustic piano. Some digital pianos are designed to also look like an upright or grand piano. Others may be very simple, without a stand.

While digital pianos may sometimes fall short of acoustic ones in feel and sound, their advantages include being smaller, weighing much less, and costing less than an acoustic piano. In addition, they do not need to be tuned, and their tuning can be modified to match the tuning of another instrument (e.g. a pipe organ). Like other electronic musical instruments, they can be connected to an amplifier or a PA system to produce a sound loud enough for a large venue or, at the other extreme, may be heard through headphones only. Some digital pianos can emulate other sounds besides the piano, the most common ones being pipe organ, electric piano, Hammond organ, and harpsichord. Digital pianos are often used in music schools and music studios as a replacement for traditional instruments.

A sound module is an electronic musical instrument without a human-playable interface such as a piano-style musical keyboard. Sound modules have to be operated using an externally connected device, which is often a MIDI controller, of which the most common type is the musical keyboard. Another common way of controlling a sound module is through a sequencer, which is computer hardware or software designed to record and playback control information for sound-generating hardware. Connections between sound modules, controllers, and sequencers are generally made with MIDI (Musical Instrument Digital Interface), which is a standardized interface designed for this purpose.

Sound modules are often rack-mountable, but are also produced in table-top form factor, particularly when the intended user is a DJ or record producer. The height of a sound module is often described in rack units. Small sound modules are mostly 1U in height, the larger models a multiplication e.g. 2U or 3U. Despite their name, most sound modules do not produce any audible sound until their output is plugged into a keyboard amplifier or a PA system.

Bass pedals are an electronic musical instrument with a foot-operated pedal keyboard with a range of one or more octaves. The earliest bass pedals from the 1970s consisted of a pedalboard and analog synthesizer tone generation circuitry packaged together as a unit. The bass pedals are plugged into a bass amplifier or PA system so that their sound can be heard. Since the 1990s, bass pedals are usually MIDI controllers, which have to be connected to a MIDI-compatible computer, electronic synthesizer keyboard, or synth module to produce musical tones. Some 2010s-era bass pedals have both an onboard synth module and a MIDI output.

Bass pedals serve the same function as the pedalboard on a pipe organ or an electric organ, and usually produce sounds in the bass range, which, in organ terminology is the 16′ stop. Some bass pedals have an 8′ stop (an octave higher) which can be used by itself or combined with the 16' stop. Bass pedals are used by keyboard players as an adjunct to their full-range manual keyboards (the keyboards played with the hands), by performers of other instruments (e.g., electric bass or electric guitar), or by themselves. Bass pedal units usually have a smaller range (13 notes) than a church pipe organ's pedal keyboard (32 notes for an American Guild of Organists standard pedalboard). Bass pedals with larger ranges are less common, but do exist, such as 17 notes (C to E), 20 notes (C to G), and 25 notes (C to C two octaves higher). As well, bass pedals usually have shorter pedals than those on a church pipe organ's pedalboard.

Thiele/Small parameters (commonly abbreviated T/S parameters, or TSP) are a set of electromechanical parameters that define the specified low frequency performance of a loudspeaker driver. These parameters are published in specification sheets by driver manufacturers so that designers have a guide in selecting off-the-shelf drivers for loudspeaker designs. Using these parameters, a loudspeaker designer may simulate the position, velocity and acceleration of the diaphragm, the input impedance and the sound output of a system comprising a loudspeaker and enclosure. Many of the parameters are strictly defined only at the resonant frequency, but the approach is generally applicable in the frequency range where the diaphragm motion is largely pistonic, i.e., when the entire cone moves in and out as a unit without cone breakups.

Rather than purchase off-the-shelf components, loudspeaker design engineers often define desired performance and work backwards to a set of parameters and manufacture a driver with said characteristics or order it from a driver manufacturer. This process of generating parameters from a target response is known as synthesis. Thiele/Small parameters are named after A. Neville Thiele of the Australian Broadcasting Commission, and Richard H. Small of the University of Sydney, who pioneered this line of analysis for loudspeakers. A common use of Thiele/Small parameters is in designing PA system and hi-fi speaker enclosures; the TSP calculations indicate to the speaker design professionals how large a speaker cabinet will need to be and how large and long the bass reflex port (if it is used) should be.