Flat Frequency Response - Term for a circuit or audio system which will pass audio signals that will vary by no more than ± 1 dB usually between 20 Hz and 20 kHz unless otherwise specified.
Fletcher Munson Curves - The set of curves showing the human's ear's frequency sensitivity versus loudness, created by researchers Fletcher and Munson. The curves show the ear to be most sensitive to sounds between 3 kHz and 4 kHz (ear canal resonances).
Floating Ground - Non-common grounding point.
Flux - The flow of magnetic energy in a circuit.
FM Stereo Separation - The FM tuner demodulator's ability to separate left and right channel signals of FM stereo broadcast. Measured in decibels, the higher the number the better.
Focus Lens - The lens in the optical block of a compact disc player which focuses the laser light onto the surface of the disc.
Focus Servo - The circuit which keeps the laser light correctly focused on the pit area of the disc.
Free Air Response - The frequency at which a speaker will naturally resonate.
Frequency - The number of wavelengths which pass a specific point in a specific time period, measured in Hertz (Hz). Cycles per second.
Frequency Dividing Network - See crossover network.
Frequency Modulation (FM) - The encoding of a carrier wave by variation of it's frequency in accordance with an input signal.
Frequency Response - The lowest and highest parts of the frequency spectrum that can be reproduced by an audio component within specific limits and tolerances.
Fs - Driver free air resonance, in Hz. This is the point at which driver impedance is maximum. "This parameter is the free-air resonant frequency of a speaker. Simply stated, it is the point at which the weight of the moving parts of the speaker becomes balanced with the force of the speaker suspension when in motion. If you've ever seen a piece of string start humming uncontrollably in the wind, you have seen the effect of reaching a resonant frequency. It is important to know this information so that you can prevent your enclosure from 'ringing'. With a loudspeaker, the mass of the moving parts, and the stiffness of the suspension (surround and spider) are the key elements that affect the resonant frequency. As a general rule of thumb, a lower Fs indicates a woofer that would be better for low-frequency reproduction than a woofer with a higher Fs. This is not always the case though, because other parameters affect the ultimate performance as well."
Fundamental Frequency - The principal component of a complex waveform having the lowest frequency.
Fuse - A device that protects electric circuits by interrupting power in a circuit when an overload occurs. Rated in amperes (amps).
Fusible Link - Designed to perform the same task as a fuse, but the resembles a wire. Fusible links are commonly used in ignition switches and other high current circuits.
Gain - The amount of amplification used in an electrical circuit.
Gauge (wire) - The diameter of a wire. The higher the number, the thinner the wire.
Giga - Prefix meaning 109 or 1,000,000,000 (1 billion in the US)
Googol - A googol is the number 10100, that is, 1 followed by one hundred zeroes.
Graphic (equalizer) - Refers to a type of equalizer with sliding controls that create a pattern representing a graph of frequency response changes.
Ground - An electrical line with the same electrical potential as the chassis of the vehicle, most commonly negative 12 volts DC.
Ground Loop - The condition created when two or more paths for electricity are created in a ground line, or when one or more paths are created in a shield or an audio cable. This can create undesirable noise such as a high pitched whine when the vehicle is running or pops and clicks when other devices are used in the vehicle.
Ground Potential - In an automobile this is the electrical potential of the vehicles chassis, specifically the chassis of the alternator when the vehicle is running. A circuit, terminal or chassis is said to be at ground potential when it is used as a reference point for other potentials in the system.
Harmonic - A weaker overtone or undertone of the original note responsible for the character of the note.
Henry / Henries (Hy) - The measurement for inductance. Coils (low pass filters) are measured in millihenries as in 6.4 mHy (6.4 millihenries).
Hertz (Hz) - The unit of measurement for frequency. 1 Hz is equal to 1 cycle per second.
High Frequency Driver - A loudspeaker specifically designed to reproduce short, high-frequency wave lengths. The driver typically has a small, lightweight diaphragm. Tweeter.
High Level Input - An input configured to accept speaker level signals.
High Pass Filter - A network of elements used to attenuate all frequencies below a predetermined frequency. Frequencies above the cutoff point pass without any effect.
Highs - Term which refers to a set of speaker components used to reproduce frequencies above 500 Hz as in a set of separates. May also refer to tweeters which are used to reproduce frequencies usually above 2.5 kHz. Not bass
IASCA - International Auto Sound Challenge Association
IIR Filter - (Infinite Impulse Response Filter) A digital filter employing a single stage, through which the signal is passed repeatedly to achieve the desired processing effect. Offers simplicity of design and lower cost than the FIR type.
Image Rejection - The rejection of the same signals that can be received at two or more points on the dial of a tuner by a single radio station (ghost, images) . Image Rejection is expressed in decibels, the higher the number the better.
Imaging - The reproduction of sound accurately so that the listener can imagine the original environment and placement of the original sound sources accurately within within that environment. The better the imaging the more analogous the reproduced sound will be to the original.
Impedance - The opposition to the flow of alternating current (AC) in a circuit. Measured in ohms .
Inductance - The ability to induce an electrical current. Measured in Henrys.
Inductive Coupling - Radiated noise that is transmitted through a magnetic field to surrounding lines.
Inductor - An electrical component in which impedance increases as the frequency of the AC decreases. Also known as coils that are used in passive crossovers. Inductors are rated in Hennes.
Infinite Baffle - A loudspeaker baffle of infinite space that has no openings for the passage of sound from the front to the back of the speaker. Also, a sealed enclosure where the internal volume is greater than the Vas of the driver.
Input Sensitivity Control - Adjusts the amount of input signal being fed to the amplifier stage to reduce distortion.
Insulation - A material that electrically isolates a conductor or thermally isolates an object from its surroundings.
Intermodulation Distortion (in loudspeakers) - Is the distortion generated in single cone speakers when the cone is reproducing a high and low frequency simultaneously. The high frequency peaks will be flattened off if the low frequency is distorted in any way.
ISO-DIN Mounting - Refers to a mounting system in which the headunit is mounted behind the dash panel with side brackets, employing factory installed trim panels.
Jacket - The outer covering on a cable or wire that may provide electrical insulation and/or resistance to abrasion, chemicals, and moisture.
Jams - Tunes, rocks, hits, sounds good, etc.
Japanese Industrial Standards Committee (JISC or JIS) - A Japanese agency that establishes and maintains standards for equipment and components.
Jewel Case - The hard plastic case that contains a compact disc.
Joule - A unit of energy equal to one watt per second.
Junk - Discarded or useless; of no value.
Kilo (k) - A prefix meaning thousand.
Kilohertz (kHz) - 1 kHz equals one thousand hertz or 1,000 times per second. Formerly kilocycles (kc).
Kirchoff's Current Law (KCL) - A law stating that the total current entering a point or junction in a circuit must equal the sum of the current leaving that point or junction.
Kirchoff's Voltage Law (KVL) - (KVL) A law stating stating that the voltage supplied to a DC circuit must equal the sum of the voltage drops within the circuit.
L - Length of wire immersed in magnetic field, in meters
Laser Diode - A semiconductor device which emits a laser beam.
LCD - Liquid Crystal Display.
Lces - The electrical inductive equivalent of Cms, in henries
Le - "This is the voice coil inductance measured in millihenries (mH). The industry standard is to measure inductance at 1,000 Hz. As frequencies get higher there will be a rise in impedance above Re. This is because the voice coil is acting as an inductor. Consequently, the impedance of a speaker is not a fixed resistance, but can be represented as a curve that changes as the input frequency changes. Maximum impedance (Zmax) occurs at Fs. "
LED - Light Emitting Diode.
Line Level - The standard preamplifier output level of a signal from an audio source other than a turntable. Usually between 100mV and 1V, but may be as high as 5V or more from some preamplifiers.
Linearity - In an audio device, the ability to accommodate the flow of the original source signal withuot distorting or altering it in any way. A component is linear if it accurately reproduces the source signal regardless of the signal's frequency.
Linearity Error - The deviation in response from an expected or theoretical straight line value for instruments and transducers (speakers).
Liquid Crystal Display (LCD) - A type of digital display made of a material that changes reflectance or transmittance when an electrical field is applied to it.
Load - The electrical demand of a process, expressed in current (amps), power (watts), or resistance (ohms).
Local / Distance Switch - Changes the sensitivity of the tuner. When switched to local (LO), the stronger local stations are received with a higher image rejection. When switched to distance (DX), the weaker, distant stations are received but with less image rejection.
Loudness Control - Intended to boost low frequencies at lower volume levels and should not be used at high volume listening levels.
Loudspeaker - An electro acoustic transducer which converts electrical audio signals at its input to audible waves at it's output. May also refer to a given driver of a multiple speaker system and not to the whole speaker system as might a speaker.
Loudspeaker Compliance - The acoustical and mechanical equivalent of capacitance. Determines how easily a speaker cone/ voice coil assembly will move when an electrical signal is applied to it.
Low Frequency Driver - A loudspeaker specifically designed to reproduce long, low-frequency wave lengths. The driver typically has a large cone, magnet structure, and voice coil. Woofer.
Low Pass Filter - A network of elements used to attenuate all frequencies above a predetermined frequency. Frequencies below the cutoff point pass without any effect.
Lows - Term which refers to a set of speaker components used to reproduce frequencies below 500 Hz as in a set of woofers. May also refer to the low frequency drivers of a set of separates. Not treble.