|
Ampere(or Amp or A): |
The unit of measurement for electrical current in coulombs per second. There is one amp in a circuit that has one ohm resistance when one volt is applied to the circuit. See Ohm's Law.
|
|
Analog: |
An audio signal that is an electrical replica of the waveform of the sound it represents. Most car stereo components are analog in nature, CD players are the exception.
|
|
Auto Reverse: |
This feature allows the user to play both sides of the cassette without having to remove it and turn it over manually.
|
|
Aux. (auxiliary) Input: |
A jack found on some head units that is used to add a second source. A portable CD player for example.
|
|
Balance: |
Control that changes the volume of the left and right stereo channels.
|
|
Band Pass Enclosure: |
A type of subwoofer enclosure where the speakers are completely inside the enclosure and all the output is directed through a port(s) on one of the sides.
|
|
Band Pass Filter: |
A device that only passes signals within a specific range of frequencies.
|
|
Best Station Memory (BSM): |
A tuner circuit that automatically presets the strongest radio stations in a listening area.
|
|
Bridging: |
Combining the left and right channel of an amplifier together into one higher powered channel. Amplifiers will normally state whether or not they can be bridged and what the minimum speaker impedance is that they can handle.
|
|
Capacitor: |
A device made up of two metal plates separated by a dielectric (insulator). Used to store electrical energy. In car audio installations, special "Power Line Capacitors" can be connected inline to aid the alternator in supplying current demands of the amplifiers. Non-polarized capacitors can be used as high pass crossovers or as components in other crossover networks.
|
|
Crossover (Network or Filter): |
An electrical circuit which divides the audio frequencies into different bands to be sent to individual speakers or amplifiers.
|
|
Decibel (dB): |
The unit to measure the difference between two levels of a sound or electrical signal. A logarithmic expression of the ratio of two such levels. An increase of 10dB represents a tenfold increase in power. Doubling power raises SPL by about 3 dB.
|
|
Detachable Face: |
A security feature found on some head units that enables the owner to remove only the control panel from the main unit, which remains in-dash, the related Detachable module is a small section only of the detachable face.
|
|
Digital: |
A component that uses digits or binary coding. A tuner may be called digital because it uses numbers in its display. Digital components are usually more stable and precise than analog components.
|
|
Digital output: |
A jack that delivers digital signals to downstream components, often via a fiber-optic cable.
|
|
DIN: |
An industry standard generally applied to the most common chassis size of dash mount head units. This is an acronym for Deutsche Industrie Normen.
|
|
DIN Cable: |
A cable containing a series of wires in a single connector. These cable are usually not interchangeable.
|
|
DNR: |
Acronym for Dynamic Noise Reduction. A noise reduction system that reduces the level of high frequencies to a low level signal.
|
|
Dolby B, Dolby C: |
A licensed tape noise-reduction system. This system boost selected frequencies during recording and attenuating them during playback. Dolby B is most common but Dolby C is more effective.
|
|
DSP: |
Acronym for Digital Signal Processor. A component that manipulates audio signals in a digital environment. This includes ambience synthesis, time alignment, and filtering.
|
|
ETR (Electronic Tuning Radio): |
A radio that not only has a digital readout, but also has its tuner on a chip. These radios generally tune in better than an analog unit and give more features such as station presets.
|
|
Equalizer (EQ): |
A device used to boost or reduce specific frequency ranges.
|
|
Frequency: |
The vibration or oscillation of sound and is measured in cycles per second called Hz (Hertz). Humans can hear frequencies between 20-20kHz.
|
|
Frequency Response: |
A specification that indicates how evenly a component or system reproduces frequencies in the audio spectrum. This specification must include a tolerance. A plus/minus decibel figure that indicates the severity of response deviations: closer tolerances are better.
|
|
Head Unit: |
A generic term for any dash-mountable source component, such as a cassette receiver or CD tuner.
|
|
High Pass Filter: |
A device that blocks signals below a specific frequency while allowing signals above that frequency to pass.
|
|
Hz (Hertz): |
The standard unit of frequency. Hz represents cycles per second. The higher the Hz figure, the higher the sound's pitch.
|
|
Impedance: |
A measurement, in ohms, of the resistance a component presents to the flow of electrical current; the lower the number, the less resistance.
|
|
Jack: |
A female connector that serves as a receptacle for a male connector.
|
|
LCD (Liquid-crystal display): |
A type of electronic readout used on the front panel of some components.
|
|
Loudness: |
An equalization circuit used in some head units that progressively emphasizes low frequencies and sometimes high frequencies as volume is reduced; can be switchable (on, off), adjustable or automatic.
|
|
Low Pass Filter: |
A device that blocks signals above a specific frequency while allowing signals below that frequency to pass.
|
|
Maximum Power: |
The maximum, or peak amount of power an amplifier is capable of producing for a short period; maximum ratings should generally be ignored, since they are usually accompanied by a substantial amount of distortion.
|
|
Midbass: |
The audio frequencies just above the Sub-bass range from around 100Hz up to 400Hz.
|
|
Midrange: |
The audio frequencies above Sub-bass but below treble that carry most of the identifying tones of speech. Usually between 300-400Hz up to 3000Hz.
|
|
MOSFET: |
Metal Oxide Semiconductor Field Effect Transistor. Used in most modern, quality car audio amplifiers in the power supply (and sometimes in the output stage.) MOSFETs run cooler than normal bipolar transistors and have a faster switching speed.
|
|
OEM: |
Original Equipment Manufacture: Synonymous with "stock"; describes the factory-installed equipment offered in new vehicles.
|
|
OHM |
The basic unit of electrical resistance: see impedance.
|
|
OHM's Law: |
A basic law of electrical 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.
|
|
Preset Scan: |
A feature that previews each preset for a few seconds; primarily found in tuners.
|
|
S/N (Signal To Noise Ratio): |
Measured in dB, the difference in level between a signal (usually a standard level) and the residual noise of the component through which it is passed; higher figures are better.
|
|
Sound Off: |
A car stereo competition.
|
|
SPL (Sound Pressure Level): |
The acoustic level of sound waves measured in dB's.
|
|
Source: |
The signal that is played through a system. Head units and CD changers are source components.
|
|
Stereo: |
The use of at least two channels-left and right.
|
|
Strongest Station Memory: |
A tuner circuit that automatically presets the strongest radio stations in a listing area.
|
|
Sub Bass: |
The lowest end of the audio spectrum. Below around 70-100Hz.
|
|
THD (Total Harmonic Distortion): |
The percentage of an audio output signal that consists of spurious harmonic, or multiples of the fundamental frequencies. These harmonics are introduced by a power amplifier or other components through which the signal passes; lower figures are better.
|
|
Tone Control: |
A head-unit or power amplifier feature that modifies the relative level of certain frequencies; most head units have separate bass and treble controls.
|
