Glossary of Audio Terms

AC : Abbreviation for alternating current.

Active crossover : Uses active devices (transistors, ICs, tubes) and some form of power supply to operate.

Amplitude : The extreme range of a signal. Usually measured from the average to the extreme.

Arc : The visible sparks generated by an electrical discharge.

Bass : The lowest frequencies of sound.

Bi-Amplification : Uses an electronic crossover, or line-level passive crossover, and separate power amplifiers for the high and low frequency loudspeaker drivers.

Capacitance : That property of a capacitor which determines how much charge can be stored in it for a given potential difference between its terminals, measured in farads, by the ratio of the charge stored to the potential difference.

Capacitor : A device consisting of two or more conducting plates separated from one another by an insulating material and used for storing an electrical charge. Sometimes called a condenser.

Clipping : Distortion of a signal by its being chopped off. An overload problem caused by pushing an amplifier beyond its capabilities. The flat-topped signal has high levels of harmonic distortion which creates heat in a loudspeaker and is the major cause of loudspeaker component failure.

CLS : The abbreviation for curvilinear linesource.

Crossover : An electrical circuit that divides a full bandwidth signal into the desired frequency bands for the loudspeaker components.

dB (decibel) : A numerical expression of the relative loudness of a sound. The difference in decibels between two sounds is ten times the Base 10 logarithm of the ratio of their power levels.

DC : Abbreviation for direct current.

Diffraction : The breaking up of a sound wave caused by some type of mechanical interference such as a cabinet edge, grill frame or other similar object.

Diaphragm : A thin flexible membrane or cone that vibrates in response to electrical signals to produce sound waves.

Distortion : Usually referred to in terms of total harmonic distortion (THD) which is the percentage of unwanted harmonics of the drive signal present with the wanted signal. Generally used to mean any unwanted change introduced by the device under question.

Driver : See transducer.

Dynamic Range : The range between the quietest and the loudest sounds a device can handle (often quoted in dB).

Efficiency : The acoustic power delivered for a given electrical input. Often expressed as decibels/watt/meter (dB/w/m).

Electrostat : Slang for 'electrostatic loudspeaker'.

Electrostatic : (A) Of or relating to electric charges at rest. (B) Produced or caused by such charges.

ESL : The abbreviation for electrostatic loudspeaker.

Headroom : The difference, in decibels, between the peak and RMS levels in program material.

Hybrid : A product created by the marriage of two different technologies. Meant here as the combination of a dynamic woofer with an electrostatic transducer.

Hz (Hertz) : Unit of frequency equivalent to the number of cycles per second.

Imaging : To make a representation or imitation of the original sonic event.

Impedance : The total opposition offered by an electric circuit to the flow of an alternating current of a single frequency. It is a combination of resistance and reactance and is measured in ohms. Remember that a speakers impedance changes with frequency, it is not a constant value.

Inductance : The property of an electrical circuit by which a varying current in it produces a varying magnetic field that introduces voltages in the same circuit or in a nearby circuit. It is measured in henrys.

Inductor : A device designed primarily to introduce inductance into an electrical circuit. Sometimes called a choke or coil.

Linearity : The extent to which any signal handling process is accomplished without amplitude distortion.

Loudspeaker : A device that converts electric signals to audible sound.

Midrange : The middle frequencies where the ear is the most sensitive.

Passive crossover : Uses no active components (transistors, ICs, tubes) and needs no power supply (AC, DC, battery) to operate. The crossover in a typical loudspeaker is of the passive variety. Passive crossovers consist of capacitors, inductors and resistors.

Phase : The amount by which one sine wave leads or lags a second wave of the same frequency. The difference is described by the term phase angle. Sine waves in phase reinforce each other; those out of phase cancel.

Pink noise : A random noise used in measurements, as it has the same amount of energy in each octave.

Polarity : The condition of being positive or negative with respect to some reference point or object.

RMS : Abbreviation for root mean square. The effective value of a given waveform is its RMS value. Acoustic power is proportional to the square of the RMS sound pressure.

Resistance : That property of a conductor by which it opposes the flow of electric current, resulting in the generation of heat in the conducting material, usually expressed in ohms.

Resistor : A device used in a circuit to provide resistance.

Resonance : The effect produced when the natural vibration frequency of a body is greatly amplified by reinforcing vibrations at the same or nearly the same frequency from another body.

Sensitivity : The volume of sound delivered for a given electrical input.

Stator : The fixed part forming the reference for the moving diaphragm in a planar speaker.

THD : The abbreviation for total harmonic distortion. (See Distortion)

TIM : The abbreviation for transient intermodulation distortion.

Transducer : Any of various devices that transmit energy from one system to another, sometimes one that converts the energy in form. Loudspeaker transducers convert electrical energy into mechanical motion.

Transient : Applies to that which lasts or stays but a short time. A change from one steady-state condition to another.

Tweeter : A small drive unit designed to reproduce only high frequencies.

Wavelength : The distance measured in the direction of progression of a wave, from any given point characterized by the same phase.

White noise : A random noise used in measurements, as it has the same amount of energy at each frequency.

Woofer : A drive unit operating in the bass frequencies only. Drive units in two-way systems are not true woofers but are more accurately described as being mid/bass drivers.