F

Farad - The basic unit of capacitance. A capacitor has a capacitance of 1F when a charge of 1 Volt across the capacitor produces a current of 1 Ampere through it. Named after Michael Faraday.

F3

The half power (-3dB) of a loudspeaker enclosure design. (Hz)

Fastglass Dome Tweeter

Tweeter that uses an exclusive fiberglass material that is both lighter and stronger than conventional materials. These tweeters are extremely efficient while delivering musically accurate high-frequencies.

Fb

The resonant (tuned) frequency of a vented box. Expressed in Hertz (Hz). A combination of the resonance frequency of the air in a Port and the resilient pressure of the air in a Ported System. Below this point the Frequency Response of a Tuned Port system rapidly Falls Off, and the system can become unstable if asked to reproduce lower frequencies at high Amplitude.

FCC

Federal Communication Commission - The U.S. government agency which oversees and regulates electronic communication.

FFT

Fast-Fourier Transform - A method by which a system is described using an impulse response. Both frequency and time data can be extracted, with room reflections removed, providing an extremely accurate analysis. Mathematical manipulation of the data is employed to view system parameters from a variety of perspectives.

Fidelity

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

Fill

Polyfill or something similar used to ""stuff"" a box. When placed inside a box, fill makes the box seem larger to the woofer, and helps break up standing waves within the box.

Filter

Any of various electric, electronic, acoustic, or optical devices used to reject signals, vibrations, or radiation of certain frequencies while passing others. Electronically, filters can be as simple as a single capacitor, or as complex as a dedicated computer circuit. For audio use the most common electronic filter is a bandpass filter, characterized by three parameters: center frequency, amplitude (or magnitude), and bandwidth. Bandpass filters form the heart of audio graphic equalizers and parametric equalizers.

FIR Filter

Finite Impulse Response Filter - A digital filter employing separate stages for each computation, offering virtual elimination of phase shift, and superior accuracy.

Fixed DIN Mount

A DIN headunit mounting system whereby no part or component is removable for security purposes.

Flashing Lights

A term used to describe the interfacing of the vehicle's parking lights, dome light, emergency lights, etc., with a security system so that the lights flash by the system.

Flat Response

An output signal in which fundamental frequencies and harmonics are in the same proportion as those of the input signal being amplified. A flat frequency response would exhibit relatively equal response to all fixed-point frequencies within a given spectrum.

Fletcher-Munson Curve

Fletcher and Munson were pioneering researchers who provided the basis of High Fidelity in the '30s. They accurately measured and published a set of plots showing the human's ear's sensitivity to loudness verses frequency. They conclusively demonstrated that human hearing acuity is essentially dependent upon loudness. The curves show the ear most sensitive to sounds in the 3 kHz to 4 kHz area. This means sounds above and below 3-4 kHz must be louder in order to be heard just as loud. For this reason, the Fletcher-Munson curves are referred to as "equal loudness contours." They represent a range of sensitivity from "barely heard," (0 dB SPL) all the way to "painfully loud" (120 dB SPL), usually plotted in 10 dB increments.

Flush Mounting

Mounting a speaker in such a way that the speaker and its Grill do not protrude above the surrounding surface. Usually, this means mounting it at the back of the baffle board (the board the speaker is mounted on).

Flux

The flow of magnetic energy in a circuit.

FL Backlight

Fluorescent illumination for the lighted portion of a liquid crystal display. Considered to be a step-up feature from EL backlight.

FM

Frequency Modulation - A method of modulation in which the frequency of the carrier voltage is varied with the frequency of the modulation voltage

Foam Infused Surround

A speaker surround design employing a foam material for improved durability and performance.

Fold Down Face

A DIN headunit whose faceplate hinges at the bottom to reveal a media loading slot. Provides a larger area on the face for the display and controls.

Former

The cylinder portion of a speaker's voice coil; the wire is wound around this cylinder to form a coil.

Fp

The free-air resonant frequency of a passive radiator. (Hz)

Free Air Resonance

The frequency at which a driver will naturally resonate.

Free Air Response

The frequency at which a speaker will naturally resonate.

Free Sound Field

A sound field without acoustic boundaries or where the boundaries are so distant as to cause negligible reflections over the frequency range of audible sound. If the boundaries exist but completely absorb the sound then a virtual free field is created, thus anechoic chambers are used to accurately measure loudspeakers for their unique properties.

Frequency

The number of vibrations or cycles completed by a signal in one second. Frequency is expressed in cycles, or more commonly, Hertz (Hz).


The range of human hearing is commonly given as 20-20,000Hz (20Hz-20kHz). One hertz (Hz) represents one cycle per second, 20Hz represents 20 cycles per second and so on. Lower numbers are lower frequencies

Frequency Counter

A device that assists in speaker parameter testing, as well as identifying the frequency of specific tones.

Frequency Response

The usable frequency bandwidth of a speaker, amplifier, or source unit. Usually stated as lower to upper frequency with a deviation in decibels, or relative loudness. Example: Frequency Response of 10Hz to 40kHz +/- 1dB.

Fs

The free-air resonant frequency of a driver. (Hz)

Full Logic Deck

A cassette mechanism where the tape operations are carried out by logic circuits rather than mechanical methods.

Fuse

A device designed to provide protection for a given circuit or device by physically opening the circuit. Fuses are rated by their amperage and are designed to blow or open when the current being drawn through it exceeds its design rating

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.