Gain - An increase in volume or amplitude (measured in dB).

Gauge (wire) - Also referred to as AWG. The diameter of a wire. The higher the number, the thinner the wire. For gauges required for install applications see the WIre Gauge Tables.

Graphic Equalizer - Refers to a type of equalizer with sliding controls that allows the user to increase or decrease the gain of a fixed frequency. The chosen frequencies are called bands. Graphic EQs will generally offer 3 to 30 bands to control. (See chart with Parametric Equalizer)

Grill - An acoustically transparent barrier meant to prevent damage to the speaker that it covers or create a more attractive appearance.

Ground - A term that describes anything having an electrical potential of zero relative to other points in a circuit. Most modern vehicles are based on a 12V negative ground system, with the metal chassis frame being the vehicle's ground.

Ground Loop - In car audio systems, all active components involved will seek a common ground with the source unit's ground. Normally, this is accomplished though the ground plane of the vehicle's chassis. Sometimes, the components will instead seek a ground path back though the cables that connect them with the source unit. This creates a ground loop which can cause system noise such as alternator whine or pops or clicks when other devices are used in the vehicle. Inline cable filters are available to correct this problem.

Haas Effect - Also known as Precedence effect, the Haas Effect describes how we identify the direction of a sound source heard in both ears but arriving at different times. Direct sound from any source first enters the ear closest to the source, then the ear farthest away. This is how we localize a sound source, as long as the sound arrival times to the ears are between 25-35 milliseconds apart. If the later arrivals are longer than this, then two distinct sounds are heard.

Harmonic - When you hear a musical note played, you are actually hearing a combination of different tones. These weaker overtones or undertones (Harmonics) of the original note that are responsible for the character of the note. This is the reason that two different instruments playing the same pitch (note) sound different.

Harmonic Distortion (Speakers) - A type of distortion caused when resonant or sympathetic ringing vibrations are added to the original sound to produce harmonics that were not present in the original signal.

Harmonic Distortion (Active Devices) - A type of distortion caused as a signal path passes through circuits (such as those in amps or processors), producing harmonics that were not present in the original signal.

Henry / Henries (Hy) - The measurement for inductance. Coils (low pass filters) are usually measured in millihenries.

Headroom - Refers to the dynamic range of amplifiers, expressed in dB. The level between the typical operating level and the maximum output level (Peak Power). Exceeding this level results in clipping.

Heat Sink - Parts of an amplifier or speaker frame used to conduct and radiate heat away from it's source

Hertz - The measurement of frequency. One hertz is equal to one cycle per second, or the complete cycle of an alternating (AC) waveform.

High Level Input - An audio input configured to accept speaker level signals.

High Pass Filter - A passive or active filter (mostly used in Crossover circuits) that permits the passage of high frequencies while suppressing lower ones. For diagrams of high pass passive crossover filters, see Passive Crossover Networks.

High Voltage Switching Power Supply - An amplifier's internal power supply that converts the vehicle's 12 volts to higher voltage for improved dynamic range and higher amp output power.

Horn - A type of speaker system principally used for high and midrange frequency reproduction. It uses a horn shaped framed (attached to a compression driver) to act as a lens to focus a sound field.

Horn Tweeter - A tweeter that uses a horn design to enhance or control it's dispersion pattern.