Free Air Resonance: The natural resonant frequency of a driver when operating outside an enclosure.

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

Frequency Response: The frequency range to which a system, or any part of it, can respond. Unless a limit of variation in intensity is stated, this specification is meaningless.

Full-range: A speaker designed to reproduce all or most of the sound spectrum.

Golden Ratio: The ratio of the depth, width, and height of a speaker enclosure, based on the Greek Golden Rectangle. Usually recommended for home speakers, difficult to use in car audio applications. The ratio: W = 1.0, Depth = 0.618W, Height = 1.618W.

Ground: Refers to a point of (usually) zero voltage, and can pertain to a power circuit or a signal circuit. In car audio, the single most important factor to avoid unwanted noise

is finding and setting a good ground.

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.

Heat Dissapation: The ability to transfer heat away from a component into the air to prevent damage to the speaker.

Hertz (Hz): A measurement of the frequency of sound vibration. One hertz is equal to one cycle per second.

High-pass Filter: An electric circuit that passes high frequencies but blocks low ones. Hiss: Audio noise that sounds like air escaping from a tire (high frequency).

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 freuency pitch.

Imaging: Listening term - it is the speakers ability to locate where each instrument or voice is located.

Impedance: The opposition of a circuit or speaker to ac current. the combined effect of a speakers'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.

Iductance (L): the capability of a coil to store energy in a magnetic

field surrounding it. It produces impedance to an AC current. Inductors are commonly used in audio as low pass crossovers.

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

Midrange (mids): The frequency range above bass but below treble carries most of the identifying tones of music or speech. It is usually from 300Hz - 400Hz to 3KHz or so.

Millihenries (mH): A measurement of inductance. Mms: The moving mass of a driver assembly normally measured in grams (g). Mono: Monophonic sound. A method for reproducing sound where the signals from all directions or sources are blended into a single channel.