Acoustic suspension

A sealed or closed box speaker enclosure. Also called a sealed enclosure, or infinite baffle. 

Audio frequency

The acoustic spectrum of human hearing, generally regarded to be between 20 Hz and 20 kHz. 

Baffle

A board or other plane surface used to mount a loudspeaker. 

Bandwidth

The range of frequencies covered by a driver or a network (crossover). 

Band-Pass filter

An electric circuit designed to pass only a certain range of frequencies. See also High-pass and Low-pass filters. 

Basket

The metal frame of a speaker. 

Bass Reflex

See ported enclosure. 

Boomy

The smearing of transients that makes bass reproduction sound muddled. 

Channel

The path an audio signal travels through a circuit during playback. 

Circuit

A complete path that allows electrical current from one terminal of a voltage source to the other terminal. 

Clipping

(1) A distortion caused by cutting off the peaks of audio signals. Clipping usually occurs in the amplifier when its input signal is too high or when the volume control is turned too high and the amplifier tries to put out too much current and it sends out direct current to the speakers. (2) when playing at loud volumes, and the cone of the driver "bottoms out" - it cannot move as far as the signal requires it to, it can produce a noise. If an amplifier or speaker is left operating in this condition, serious damage may occur. 

Crossover Network (Filter)

An electric circuit or network that splits the audio frequencies into different bands for application to individual speakers. See Electronic and Passive Crossover. 

Damping

The reduction of movement of a speaker cone, due either to the electromechanical characteristics of the speaker driver and suspension, the effects of frictional losses inside a speaker enclosure, and/or by electrical means. 

Decibel (dB)

(1) A logarithmic scale used to denote a change in the relative strength of an electric signal or acoustic wave. It is a standard unit for expressing the ratio between power and power level. An increase of +3dB is a doubling of electrical (or signal) power; an increase of +10dB is a doubling of perceived loudness. The decibel is not an absolute measurement, but indicates the relationship or ratio between two signal levels. (2) SPL (sound pressure level) can be measured in dB. 

Diaphragm

The part of a dynamic loudspeaker attached to the voice coil that moves and produces the sound. It usually has the shape of a cone or dome. 

Dispersion

The spreading of sound waves as it leaves a speaker. 

Distortion

Any undesirable change or error in the reproduction of sound that alters the original signal. 

Dome Tweeter

A high frequency speaker with a dome-shaped diaphragm. 

Driver

A loudspeaker unit, consisting of the electromagnetic components of a speaker, typically a magnet and voice coil that actually converts electrical energy into sound. - cone, dome, planar 

Dynamic range

The range of sound intensity a system can reproduce without compressing or distorting the signal. 

Efficiency rating

The loudspeaker parameter that shows the level of sound output when measured at a prescribed distance with a standard level of electrical energy fed into the speaker. 

Electronic Crossover

Uses active circuitry to send signals to appropriate drivers. Usually more efficient than passive crossovers, however requires additional amplifiers to drive each frequency band.-- Digital, passive, electronic 

Enclosure

The box that contains the driver(s). 

Equalizer

Electronic device used to boost or attenuate certain frequencies. "EQ" 

Filter

Any electrical circuit or mechanical device that removes or attenuates energy at certain frequencies. See Crossover Network. 

Flat Response

The faithful reproduction of an audio signal; specifically, the variations in output level of less than 1dB above or below a median level over the audio spectrum. 

Frequency

The number of waves (or cycles) arriving at or passing a point in one second, expressed in hertz (Hz). 

Frequency Response

The frequency range to which a system, or any part of it, can respond. 

Full-range

A speaker designed to reproduce all or most of the sound spectrum. 

Harmonic

The multiple frequencies of a given sound, created by the interaction of signal waveforms. 

Harmonic Distortion

Harmonics artificially added by an electrical circuit or speaker, and are generally undesirable. It is expressed as a percentage of the original signal. See THD. 

Hertz (Hz)

A measurement of the frequency of sound vibration. One hertz is equal to one cycle per second. The hertz is named for H.R. Hertz, a German physicist. Also a good place to rent a car when you're on vacation. 

High-pass Filter

An electric circuit that passes high frequencies but blocks low ones. See Band-pass and Low-pass filters. 

Horn

A speaker design using its own funnel shaped conduit to amplify, disperse, or modify the sounds generated by the internal diaphragm of the speaker. 

Hum

Audio noise that has a steady low frequency pitch often caused by interference from the AC power line.

Impedance

The opposition of a circuit or speaker to ac current; the combined effect of a speaker's resistance, inductance, and capacitance that opposes the current fed to it. It is measured in ohms and varies with the frequency of the signal. 

Infinite Baffle

A flat surface that completely isolates the back wave of a driver from the front. 

Kilohertz (kHz)

one thousand hertz. 

Low-Pass Filter

An electric circuit designed to pass only low frequencies. See Band-pass and High-pass filters. 

Lobing

The tendency of a speaker system that consists of more than one driver to produce a lobed frequency response in space with in-phase reinforcement (lobes) from the various drivers occurring at some elevations and out-of-phase opposition (nulls) at points between the lobes. 

Midbass

Mid level bass, usually frequencies just above the sub-bass range, from around 100-400Hz or so. 

Midrange (mids)

The frequency range above bass but below treble that carries most of the identifying tones of music or speech. It is usually from 300-400Hz to 3kHz or so. 

Noise

Any undesirable sound reproduced in an audio system. 

Octave

A range of tones where the highest tone occurs at twice the frequency of the lowest tone. 

Ohm

A unit of electrical resistance or impedance. 

Ohm's Law

A basic law of electric circuits. It states that: the current [I] in amperes in a circuit is equal to the voltage [E] in volts divided by the resistance [R] in ohms; thus, I = E/R. 

Out of Phase

When your speakers are mounted in reverse polarity, i.e., one speaker is wired +/+ and -/- from the amp and the other is wired +/- and -/+. Bass response will be very thin due to cancellation. 

Passive Crossover

Uses inductors (coils) and capacitors to direct proper frequencies to appropriate drivers. 

Phase

Refers to the timing relationship of two or more signals or soundwaves. It's especially important to be sure that your stereo speakers are playing "in phase." This means that the drivers (cones and domes) of your right and left speakers are moving in and out at the same time. If your speakers are out of phase you'll hear significantly less bass, and instead of producing a strong center image, the sound tends to stay localized at the speakers. 

Phase Coherence

The relationship and timing of sounds that come from different drivers. 

Phase Distortion

A type of audible distortion caused by time delay between various parts of the signal; can be caused by equalizers. 

Polarity

The orientation of magnetic or electric fields. The polarity of the incoming audio signal determines the direction of movement of the speaker cone. Must be observed when wiring speakers, so that they are "in phase". See Out of Phase. 

Ported Enclosure

A type of speaker enclosure that uses a duct or port to improve efficiency at low frequencies. Excellent design for lower power systems, as the port often adds up to +3dB to low frequency efficiency.   It also introduces a resonance into the system.

Resonance

the tendency of an object to vibrate most at a particular frequency. 

Resonance Frequency

the frequency at which the speaker tends to vibrate most at a certain frequency. 

Resistance (Re)

in electrical or electronic circuits, a characteristic of a material that opposes the flow of electrons. Speakers have resistance that opposes current. 

Roll-off (cut-off)

the attenuation that occurs at the lower or upper frequency range of a driver, network, or system. The roll-off frequency is usually defined as the frequency where response is reduced by -3dB. 

Sealed enclosure

air tight enclosure that completely isolates the back wave of the driver from the front. 

Signal

the desired portion of electrical information. 

Signal-to-noise (S/N)

the ratio, expressed in dB, between the signal and noise. 

Sinewave

the waveform of a pure alternating current or voltage. It deviates equally above a zero point to a positive value and an equal negative value. Audio signals are sinewaves or combinations of sinewaves. 

Sound Pressure Level (SPL)

the loudness of an acoustic wave stated in dB that is proportional to the logarithm of its intensity. 

Standing wave

a buildup of sound level at a particular frequency that occurs when any dimension of the room is equal to any multiple of the wavelength. You would hear it as a peak in the frequency response of the room. 

Subwoofer

a loudspeaker designed to reproduce only bass frequencies. 

Timbre

the quality of a sound related to its harmonic structure. Timbre is what gives a voice or instrument its sonic signature & why a trumpet and a saxophone sound different when they play the same note. 

Three-way

a type of speaker system composed of three ranges of speakers, specifically a woofer, midrange, and tweeter. 

Total Harmonic Distortion (THD)

the percentage, in relation to a pure input signal, of harmonically derived frequencies introduced in the sound reproducing circuitry and hi-fi equipment (including speakers). 

Transient Response

the ability of a speaker to respond to any sudden change in the signal without blurring (smearing) the sound. A speaker that can react quickly to rapid changes in sound has "good transient response". 

Treble (highs)

the upper end of the audio spectrum reproduced by tweeters, usually 3-4kHz and up. 

Tweeter

a speaker designed to reproduce the high or treble range of the sound spectrum. 

Two-way

a type of speaker system composed of two ranges of speakers, usually a woofer and tweeter. 

Voice coil

the wire wound around the speaker former. The former is mechanically connected to the speaker cone and causes the cone to vibrate in response to the audio current in the voice coil. 

Volt (E)

a unit of measurement used to measure how much "pressure" is used to force electricity through a circuit. 

Watt

a unit of electrical power. A watt of electrical power is the use of one joule of energy per second. Watts of electrical power equals volts times amperes. 

Wavelength

the length of a sound wave in air. It can be found for any frequency by dividing the speed of sound in air (1120 feet per second) by the frequency of the sound, or: WL = 1120 / Freq. 

Woofer

a bass loudspeaker designed to reproduce low-frequency sound only. A woofer and subwoofer are usually the similar type of loudspeaker, but their application (crossover frequency) differentiates them.