Glossary of Audio Terms

See: XLR

A device made up of two metallic plates separated by a dielectric (insulating material). Used to store electrical energy in the electrostatic field between the plates. It produces an impedance to an AC current and block DC.

A characteristic of a microphone's pickup, notably strong sensitivity to material presented to the front of the microphone, while sensitivity falls off from sources arriving at an angle of 90

See: Category 5 Cable

See: Category 5 Enhanced Cable

See: Category 6 Cable

Unshielded twisted-pair (UTP) data grade cable (usually 24 AWG). CAT 3 cables are characterized to 16 MHz and support applications up to 10 Mbps. Typically used for voice telephone and 10Base-T Ethernet systems.

Unshielded twisted-pair (UTP) data grade cable (usually 24 AWG). CAT 5 cable runs are limited to 100 meters (328 feet) due to signal radiation and attenuation considerations. Longer runs are vulnerable to electromechanical interference. CAT 5 cables are characterized to 100 MHz and support applications up to 100 Mbps. Most common application is 100Base-T Ethernet systems. (With the release of ANSI/TIA/EIA-568-B, CAT 5 is no longer recognized and is officially replaced by CAT 5e)

Same as CAT 5 cable except a plastic rib runs through the center of the cable, separating the pairs, in order to reduce cross talk. The plastic rib also maintains the proper geometry along the whole cable. Contrary to popular belief, it DOES NOT extend the bandwidth (the rated bandwidth is 100 MHz).

A 300 MHz cable.

Consumer Electronics Association. The mission of the CEA is to grow the consumer electronics industry.

See: Cross Talk

A Chip-Amp is the entire Output Section of an amplifier contained in a silicon microchip about the size of a postage stamp. All of the components and traces of the section are miniaturized to near microscopic sizes. These Chip-Amps have great value in certain audio products including cell phones, computer speakers, and powered headphones for example. They can even reach output levels of up to 50 Watts. But they can also be added together for larger output power. Five chip-amps chained together could supply up to 250W. However, the chip-amps are not generally producing clean, quiet signal. They are also not particularly rugged. While size and cost can be saved, it is at the direct expense of sound quality and long-term reliability.

The other drawback to Chip-Amps is the actual electronic design of the Output Section. With a Chip-Amp, this critical part of the amplifier is designed by a microchip manufacturer, not an amplifier design engineer. With QSC Powered Loudspeakers, the power amplifiers are designed front to back by QSC engineers. They use discreet components selected for the audio quality, precision and long-life. They also capitalize on over 30 years of experience in the design and manufacture of amplifiers. Simply put, there is no better power amplifier built into a loudspeaker on the market today.

AKA port distortion, port turbulence. Distortion product resulting from the movement of air over abrupt discontinuities

Meaning "around the ear". In headphones with earpieces surrounding the ear and pressing against the side of the head, forming a seal to reduce ambient noise leakage.

An amplifier output circuit design where operation is the intermediate case. Here both devices are allowed to be on at the same time (like in Class A), but just barely. The output bias is set so that current flows in a specific output device appreciably more than a half cycle but less than the entire cycle. That is, only a small amount of current is allowed to flow through both devices, unlike the complete load current of Class A designs, but enough to keep each device operating so they respond instantly to input voltage demands. Thus, the inherent non-linearity of class B designs is eliminated, without the gross inefficiencies of the Class A design. It is this combination of good efficiency (around 50%) with excellent linearity that makes class AB the most popular audio amplifier design.

An amplified in which the bias is set so that current flow in a specific output device is zero when not stimulated by an input signal. Essential, Class B amplifier operations are the opposite of Class A.

This high-efficiency technique uses cascaded Class AB output stages; each connected to a different power supply voltage, with the magnitude of the input signal determining the transistors to be used. Using two power supplies improves efficiency enough to allow significantly more power for a given size and weight. Class G is becoming common for pro audio designs. [Historical note: Hitachi is credited with pioneering Class G designs with their 1977 Dynaharmony HMA 8300 power amplifier.]

An amplifier output circuit design, which involves changing the power supply voltage from a lower level to a higher level when larger output swings are required. There have been several ways to do this. The simplest involves a single Class AB output stage that is connected to two sets of power supply rails by diodes or transistor switches. The design is such that for most musical program material, the output stage is connected to the lower supply voltage, and automatically switches to the higher rails for large signal peaks [thus the nickname railswitcher]. Another approach is Class G. QSC's lowest-powered amplifiers use Class AB, while the higher-powered models use Class H. Class H circuitry adds cost and complexity, but can drastically improve the electrical efficiency over that of a class AB output section of the same power rating.

See: clipping

A specialized type of limiter built into a power amp. It is triggered not by signal exceeding a defined threshold, but by clipping or other non-linearity in the output section.

Clipping occurs in an amplifier circuit when the input signal, multiplied by the gain, results in a signal that exceeds the circuit

A single copper conductor, surrounded by a thick layer of insulation, covered by heavy copper shielding. It is a constant-impedance unbalanced transmission line.

Refers to a sound characteristic that adds something not in the original sound. The coloration may be euphonically pleasant, but it is not as accurate of the original sound

The stiffness of a speaker suspension.

A microphone whose condenser is created by stretching a thin diaphragm over the front of a metal disc. By placing the two surfaces close together, an electrical capacitor is created whose capacitance carries as a function of sound pressure. Any change in sound pressure causes the diaphragm to move, which changes the distance between the two surfaces. If the capacitor is first given an electrical charge (polarized) then this movement changes the capacitance, and if the charge is fixed, then the backplate voltage varies proportionally to the sound pressure. In order to create the fixed charge, condenser microphones require external voltage (polarizing voltage) to operate.

A microphone that receives its entire signal from being in contact with a particular surface and the resulting mechanical vibrations, as opposed to airborne sound waves.
See: Piezo microphone

A unit designed for sound absorbsion/diffusion for use in corners of rooms.

A circuit consisting of filters to divide the frequency spectrum of an audio signal into bands that can be better handled by individual loudspeakers. Crossovers can be "active", requiring an electrical power source and actually consisting of multiple amplifier circuits, or "passive" which is comprises only of passive components. A 2-way crossover consists of a low pass filter and a high-pass filter while a 3-way crossover adds a band-pass filter. Crossovers can contain various types of filters and crossover points to meet many different speaker design requirements.
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A frequency divider. Crossovers are used in loudspeakers to route the various frequency ranges to their appropriate drivers. Many crossovers contain various filters to help stabilize the impedance load of the loudspeaker and or shape the frequency response.
See: Passive Crossover; Active Crossover

Undesired capacitive, inductive, or conductive coupling from one circuit, part of a circuit, or channel, to another.

The amount of electric charge flowing past a specified circuit point per unit time, or the rate of flow of electrons, usually measured in amperes. Symbol: i (usually small-signal AC) or I (DC or AC)

An amplifier circuit design in which current flows through the active device(s)-i.e., transistors, FETs, or tubes-throughout the entire signal waveform. Class A can offer superb linearity and lack of distortion, but at the heavy expense of efficiency.