Acoustic absorption
The sound deadening (absorptive) characteristics of any substance. The reference unit of absorption is one sabine which is equal to the sound "absorbed" by a one square foot opening through which sound passes (open hole).

Acoustics
A science dealing with the production, effects, and transmission of sound waves through various mediums. Includes the effects of reflection, refraction, diffraction, absorption, and interference.

Amplification
Increase in signal level, amplitude or magnitude.

Amplifier
A device which increases the level of a signal (by increasing the voltage or current). Some amplifiers are used to isolate or control a signal, and may not increase level -or may actually decrease the level (line out converter, head amp).

Amplifier, power
An amplifier which is designed for driving loudspeakers and consequently has higher power output capability than a line amplifier or preamplifier.

Analog
An electrical signal whose frequency and level vary continuously in direct relationship to the original acoustical sound waves. "analog" also may refer to a control or circuit which continuously changes the level of a signal in a direct relationship to the control setting.

Attenuator
Used decreasing the strength of a signal.

Balance control
A knob that lets you balance one pair of speakers, left to right.

Bandwidth
Refers to the "space" in the frequency response of a device through which audio signals can pass (between lower and upper frequency limits, those points where the signal level has rolled off 3 db).

Basket
This is the rigid frame of the speaker; it supports all the speaker components: cone, magnet, voice coil, terminals, grill and mounting holes.

Bass
The frequency range covering approximately 20-1000 Hz.

BBE Processing
Improves the overall clarity of any audio system by realigning the phase relationships between the lows, mids and highs. Produces sparkling clear highs and tight well defined bass. Vocals and instruments have more presence and better imaging.

Bi-amplification
A stereo, or amplifier, that is "bi-amped" uses separate power amplifiers for the woofers and the mid-range/tweeters in a speaker system. In a bi-amped system, the audio signal from the radio or tape is passed to an electronic crossover which divides the signal into bass and mid-range/treble signals. Each of these signals is then sent to its own independent amplifier and speakers. Bi-amplification offers the advantage of more sound with fewer watts, less phase error due to elimination of passive crossover. Two 5-watt amps can play louder with less distortion than a single 10-watt amp, used conventionally, and since each such amp has only part of the music to handle, it can do its job with less distortion. Bi-amplification also gives you a more precise bass and tone control.

Bobbin
A tube (most commonly made of plastic or metal) which is attached to the back of the speaker cone. The voice-coil is wound around the bobbin.

Boomy
Usually refers to excessive bass response, or a peak in the bass response of a recording, playback or sound reinforcement system. When such a condition exists, it may seem that all you hear is the '"boom, boom, boom" of musical instruments playing in this dominant low frequency range.

Coaxial
A coaxial speaker has a large cone for the low range, and a smaller tweeter for the high spectrum. There is a cross-over network which divides and routes the signal to the correct driver.

Cone
The part of an electrodynamic speaker that is shaped like an inverted cone. Usually made of paper or plastic, however, there are many materials used to make cones like new lightweight fibres or the most common being rigid and light injection moulded poly-propylene (IMPP). The forward/backward movement of this part causes the air pressure variations we perceive as sound. 

Crossover frequencies
The frequencies at which a passive or electronic crossover network divide the audio signals -which are then routed to the appropriate speakers. Crossover frequencies are expressed in hertz (hz).

Crossover network
A unit which divides the audio spectrum into two or more frequency bands.

Crosstalk (channel separation)
Crosstalk is the amount of signal that leaks from one stereo channel into the other, or from one tape track into another. It is expressed in decibels, with the higher the value the better. Channel to channel crosstalk should be at least 30 db, with 40 db being very good.

Db
The "db" (decibel) is a unit of measurement for ratios of sound level, power, voltage, and other quantities. The db is only meaningful when referenced to some actual value (e.g., speaker output: 93 db at one meter with 1 watt of input power).

Db spl
Spl is sound pressure level (i.e., an acoustical measurement). One db spl is the smallest audible difference in sound level. 0 db spl is 0.0002 dynes/square centimeter or 20 micro-pascals. It is also the threshold of human hearing at 1 khz (the threshold of pain is between 120 and 130 db spl).

D-BaSS
This is a Sony Exclusive and this essentially is a 3 way switch on their products (notably amps) that lets you boost bass by 5, 10 or 15 dB at 75hz. This increases the deep bass at all volumes without cluttering the midrange, the way a typical bass boost might.

Directionality
Speakers radiate their sound in an angle that becomes narrower and narrower as the sound frequency becomes higher. Therefore, a tweeter is very directional, and a bass woofer is very non-directional.

Dispersion
Dispersion is another word for distribution of sound. The bass tones of a speaker are basicall y non-directional, and in a car, fill-up space. Treble, or high sounds, are very directional.

Distortion
Sound which is modified or changed in some way is called distortion. It can be caused by equipment which doesn't faithfully reproduce the original input signal. The percentage of distortion is a measure of the amount of signal change produced by a component. Any good amplifier states its power in terms of rms (root mean square), or continuous power. That is, how much power it puts out continuously with a minimum of unwanted noise, or total harmonic distortion (thd). Many amplifiers list their power in peak terms, or how much power the amp will put out in a peak burst, but not hold continuously. Such amps generally have a high distortion figure, if shown at all. In a speaker, distortion is produced by several things, most related to poor construction. For example, poor alignment of the voice coil in the magnet gap can cause uncontrolled vibrations of the cone. Voice coil rubbing is the most common cause of speaker distortion, generally caused by being overdriven. 

Dolby noise reduction
Dolby is a special, patented, noise reduction system that increases dynamic range of dolby encoded broadcasts and decreases background hiss by about 10 db. Dolby encoded tapes are recommended because of superior signal- to-noise ratio, and increased dynamic range.

Driver
Another name for a loudspeaker; usually the term is used when the loudspeaker is coupled to a "horn" for acoustic coupling and controlled dispersion of sound.

Dynamic range
The difference, in decibels, between the loudest and the quietest portions of a musical performance (or between the maximum signal level and the noise floor of electronic equipment).

Easy EQ
This is a Pioneer exclusive and has pre-programmed EQ curves which typically are Super Bass, Powerful, Natural, Vocal or Flat. It also has a Custom preset where it can store your user setting.

Electrostatic speaker
A speaker which uses two pieces of metallic foil separated by a sheet of dielectric (as opposed to the cone and voice coil assembly on a cone-type speaker). A constant voltage is applied to the foils to maintain a steady attraction between them. As a music signal is superimposed over the constant voltage, the foil moves much in the same way that a speaker cone moves. The movement of the foil causes a disturbance of the air which in turn generates sound waves.

Equalizer (graphic)
A graphic equalizer is a sophisticated frequency control device. It can come with the dual function of being an external amplifier, or it can be passive, used as a pre-amp. Equalizers divide the frequency range into several sections, from low bass sounds to high treble sounds, with each control allowing a plus or minus range of 10-12 db. With an equalizer you have the ability to tune your car sound to your listening preference.

Excursion
This term refers to how far forward/backward a speaker can move.

Fader
A fader is a control that allows you to balance the sound in a four-speaker system from front to rear. When used with a balance control, you can adjust the sound level from front to rear, and from right to left.

Fidelity
A term used to describe the accuracy of recording, reproduction or general quality of audio processing.

Frequency
The rapidity of change in current or voltage in an electrical signal or of air pressure in an acoustical (sound) signal. Frequency is measured in cycles per second; 1 cycle per second (cps) is 1 hertz (hz). The higher a note on the musical scale, the higher its frequency.

Frequency response
The range of frequencies which a device or audio system will pass. "frequency response" has no meaning unless a tolerance is specified; i.e., from ( ) hz to ( ) khz, and, most importantly, t( ) db.

Hertz
A unit of measurement for frequency, equal to one cycle per second. Named after the physicist H.R. Hertz. Commonly abbreviated Hz.

High frequency driver
A loudspeaker designed specifically to reproduce the short, high frequency wavelengths. A high frequency driver typically has a small, lightweight diaphragm.

High-pass filter
A network of elements which attenuate all frequencies below a pre-determined frequency selected by the designer. Frequencies above cutoff are passed without any effect.

Impedance
Opposition to the flow of an alternating current (music is one form of alternating current). Although impedance and resistance share the same unit of measurement, the Ohm, they are not the same thing. In an electrodynamic speaker, the impedance varies with the frequency of the signal being applied to it.

Loudness contour
The human ear does not hear low frequencies well at low volume levels. There- fore, a loudness control boosts, or enriches the low bass sounds when the volume is turned down. Ideally, this should not be used at high volume listening levels.

Loudspeaker
An electroacoustic transducer that converts electrical audio signals at its input to audible sound waves at its output. May be the same as "speaker". In a multiple driver system, the term "loudspeaker" may refer to a given driver whereas the term "speaker" may refer to the overall system, including all drivers, crossover network and the enclosure.

Low-pass filter
A network of elements which attenuate all frequencies above a predetermined frequency selected by the designer. Frequencies below cutoff are passed without any effect.

Magnet weight
As a general rule the larger the magnet the larger each component must be; i.e. Cone, voice coil, basket. However, efficient speakers have magnet weight in pro- portion to the other components. Be suspicious of huge magnets in relation to basket sizes such. Oversized magnets can reduce responsiveness of the cone too.

Magnetic structure
That part of the loudspeaker comprising the magnet, pole piece, top plate, and back plate.

Midrange driver or component
A loudspeaker specifically designed to reproduce the frequencies in the middle of the audible bandwidth. Most musical energy lies in the mid-band. A midrange driver is typically between three and eight inches in diameter.

Mosfet:
MOSFET amplifiers are recognised by audiophiles as offering unsurpassed audio quality. MOSFET amplifiers offer extremely high linearity and practically eliminate distortion, resulting in a second-to-none performance.

Ohm
A unit of measurement for resistance and impedance. Represented by the symbol which is the Greek letter Omega.

Piezo electric tweeter
A very efficient, highly sensitive, highly directional tweeter which operates without a magnet or crossover.

Power handling capability
In speaker systems, the maximum amount of power that can be safely accommodated without damage. The power handling capacity will vary depending on the frequency and length of time the signal is applied.

Pre-amp
A pre-amp includes all of the controls for regulating tone, volume, and channel balance. It is a circuit unit which takes a small signal and amplifies it sufficiently to be fed into the power amplifier for further amplification.

Pre-amp fader
This circuitry provides an effective level control between two amplifiers.

Resonance
The lower end of the frequency response spectrum (bass tones) is heavily influenced by the resonance (pitch) of the speaker. If you tighten a drum it raises its resonance. This same effect is achieved in a speaker by stiffening its cone suspension. A speaker with good resonance features good bass response without bottoming out (rattling or vibrating).

Sensitivity (loudspeaker sensitivity)
The sound pressure level a speaker produces when fed by a given input power, measured at a specified distance on-axis (directly in front of the speaker). Usually specified in db spl at 1 meter, 4 feet or 30 feet, and with a 1 watt or 1 milliwatt input signal.

SFEQ:
SFEQ lets you control bass and treble settings for the front and rear independently. This way you can design your complete car sound so that the vocals are front stage to produce as natural as possible effects. SFEQ lets you blend the perfect sound combo for your preferred sound experience and in some cases makes your car setup sound very similar to components, when you’re actually running coaxials. This is found on most good Pioneer headunits.

Signal- to-noise ratio (sin)
This figure specifies, in decibels, how quiet and hiss-free the background will be in relation to the music, with a good signal. A rating of 60 db, for example, means that the signal is 1,000 times stronger than the noise.

Source Level Adjuster (SLA):
Allows you to independently adjust the volume ratio between all of the headunit's sources (using the FM volume level as a reference), so the start-up volume between sources will always be the same. This is found on most Pioneer units.

Spl (sound pressure level)
An acoustic measurement of the sound energy, usually measured in db spl (see "db spl"). Not the same as loudness, which involves subjective measurement based on the human ear's differing sensitivity at different frequencies and levels.

SubWoofer
A loudspeaker made specifically to reproduce the lowest of audio frequencies, approximately between 20 hz and 125 hz.

Transducer
Any device which converts energy from one form to another, as electrical to acoustic or vice-versa. For example, loudspeakers and microphones are two types of transducers.

Treble
The high end of the audio spectrum, covering from approximately 4 kHz to 20 kHz.

Tweeter
A loudspeaker used in a 2-way or more complex speaker system to reproduce only the treble or high frequencies of the audible spectrum (see "high frequency driver").

Voice coil
This is a coil of wire inside the speaker which is attached to the bobbin. When an audio signal flows through this, it causes the speaker cone to move forward/backward (because a speaker is an electromagnetic device)

Watt
A unit of measure for electrical or acoustical power.

Woofer
A loudspeaker or driver in a 2-way or more complex speaker system that is used to reproduce onl y the bass or lower part of the audible spectrum.