Hard Dome-Tweeter

A characteristic of some Dome tweeters in which the dome is made of some light, hard metal such as neodymium, titanium, or some of the more rigid plastic compounds. The differences in reproduction between hard and soft dome tweeters, are distinctive, but very subtle. Pay close attention to how these sound before purchase.

Harmonic

Also called overtones, these are vibrations at frequencies that are multiples of the fundamental. Harmonics extend without limit beyond the audible range. They are characterized as even-order and odd-order harmonics. A second-order harmonic is two times the frequency of the fundamental; a third order is three times the fundamental; a fourth order is four times the fundamental; and so forth. Each even-order harmonic: second, fourth, sixth, etc.-is one octave or multiples of one octave higher than the fundamental; these even-order overtones are therefore musically related to the fundamental. Odd-order harmonics, on the other hand: third, fifth, seventh, and up-create a series of notes that are not related to any octave overtones and therefore may have an unpleasant sound. Audio systems that emphasize odd-order harmonics tend to have a harsh, hard quality.

Harmonic Distortion

Distortion that is harmonic in nature, following the natural harmonics of the original signal. This is the least noxious form of distortion.

Harness

The universal name for a bundle or loom of wires that compose the wiring for a system.

HD CD

High-Definition Compact Disc. A proprietary system by Pacific Microsonics that requires special encoding during the recording process. Some observers report HDCD discs as having better sound. To gain the benefits requires having special HDCD in your CD player.

Headroom-Amplifiers

A term related to the dynamic range of amplifiers, used to express in dB, the level between the typical operating level and the maximum output level (onset of clipping). For example, a nominal +5 dBu system that clips at +25 dBu has 20 dB of headroom. Because the term depicts a pure ratio, there are no units or reference-level associated with headroom, only relative "dB." Therefore headroom expressed in dB accurately refers to both voltage and power. Which means the example above has both 20 dB of voltage headroom, and 20 dB of power headroom.

Head Unit

A factory or aftermarket car radio, especially with CD/MD/DVD/MP3 or cassette.

Hearing Sensitivity

The human ear is less sensitive at low frequencies than in the midrange. Turn your volume knob down and notice how the bass seems to"disappear". To hear low bass requires an adequate SPL level. To hear 25Hz requires a much higher SPL level than to hear 250Hz. In the REAL world, low frequency sounds are reproduced by large objects; bass drums, string bass, concert grand pianos, etc. Listen to the exhaust rumble of a 454 cubic inch V8 engine vs. the whine of the little four banger. The growl of a lion vs. the meow of your favorite kitty. As frequency decreases we perceive more by feel than actual hearing and we lose our ability to hear exact pitch.

Heat Dissipation

The function of transferring heat away from a component into the air to prevent damage to the output section of an amplifier or the voice coil of a speaker.

Heat Sink

Part of the frame of the speaker used to conduct and radiate heat away from the motor assembly.

High-Pass Filter

A circuit that allows high frequencies to pass but rolls off the low frequencies. When adding a subwoofer it is often desirable to roll-off the low frequencies to the main amplifiers and speakers. This will allow the main speakers to play louder with less distortion. High-pass filters used at speaker level are usually not very effective unless properly designed for a specific main speaker.

High Current Design

An amplifier that is able to supply the electrical current demanded by a reactive, low impedance driver, while maintaining output voltage.

High Frequency

Refers to radio frequencies in the 3-30 MHz band. In audio it usually refers to frequencies in the 5-10 kHz band.

High Level Input

An input configured to accept speaker level signals.

High Output Digital Amplifier

A more efficient amplifier design that delivers much more power, with lower distortion than conventional amplifier designs.

High Power Output

Speaker level outputs driven by an amplifier, typically at least 35 watts max per channel.

High Voltage Converter

(15VDC DC/DC) A component that converts the vehicle's 12 volts to a dual swing, 15 volt supply, typically used in step up, 4 volt preamp output models

High Voltage Switching Power Supply

A power supply that converts the vehicles 12 volts to higher voltage for improved dynamic range and higher preamp output levels.

HOP

Highly Oriented Polyolefine - A speaker cone material which combines high strength, low weight, and low resonance resulting in improved transient response, higher power handling, and flatter frequency response.

Housekeeping

(Cellular) - A part of a program which attends to chores, such as setting variables to zero, rather than being involved in computations.

HPF

High Pass Filter - A network of components which attenuate all frequencies below a predetermined frequency selected by the designer. Frequencies above cut-off are passed without any effect.

HPL

High Polymer Laminate - A type of speaker cone that consists of a natural substrate with a coating of a special polymer to reduce cone resonance and increase strength. HPL cones are extremely durable and keep their shape under extreme conditions, providing tight bass and excellent dynamics.

Hyperbaric Resonator Impulse

An audible event characterized by a sudden and often unexpected pressure wave emanating from a vent port with a driver whose energetic and propulsive energy transitions, are generated by a process involving the chemical modification of legumes. This phenomenon frequently produces olfactory irritation in associated groups in consequence. This event is also know as a Farsical Audio Report Transient.

Hz

Hertz - The unit of frequency within a specific period, such as alternating or pulsating current; 1 Hz = 1 cycle per second.