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Home Theater - Movies Glossary
Category: Film and Animation > Home Theater's AV Glossary
Date & country: 19/08/2008, US
Words: 229

Sound-Pressure Level. Measured in dB.

A speaker designed to reproduce very low bass frequencies, usually those below about 80 Hz.

The elements that hold a loudspeaker driver's moving parts together, allows them to move, and helps return them to rest. Most commonly, these include the flexible surround around the outer rim of the driver and the spider on the underside of the diaphragm. See Spider.

Tactile Transducer
A device that turns electrical energy into mechanical energy, usually used to shake the seating in a theater. Effective in providing visceral impact without increasing the system's actual SPL level.

Total Harmonic Distortion

Certification program for home theater equipment. Uses some proprietary features, but mostly assures a base quality level for a given room size. (See THX Select or Ultra.) Is compatible with any and all soundtrack formats. Stands for either Tom Holman's eXperiment, after the engineer who drafted the original standard, or is named after the company'...

THX Select
Certification program for speakers and receivers that assures a base level of quality and performance when played in a room that's between 2,000 and 3,000 cubic feet.

THX Ultra
Certification program for speakers, receivers, and amplifiers that assures a base level of quality and performance when played in a room that's greater than 3,000 cubic feet.

THX Ultra 2
The newest certification from THX, THX Ultra 2 requires amplification for seven channels, boundary compensation for subwoofers, and stricter requirements for amplifiers and speakers than THX Ultra. Dipole speakers are used for the side surround channels. Monopole speakers are used for the surround back channel and are placed next to each other. The...

Any device that converts one form of energy into another form of energy, specifically when one of the quantities is electrical. Thus, a loudspeaker converts electrical impulses into sound (mechanical impulses), a microphone converts sound into electrical impulses, a solar cell converts light into electricity, etc.

Transmission Line
A (sub)woofer cabinet design where the driver is mounted at one end of a tube with the same diameter as the radiating area of the driver and a length of 1/4 wavelength of the 3dB down frequency. This 'tube' may or may not be round and may be folded to decrease the size of the cabinet.

See Receiver.

A speaker driver designed to reproduce high frequencies; usually those over approximately 5,000 to 10,000 Hz.

Even distribution across a given space. In video, uniformity can refer to the distribution of light (hot spotting) or color.

Unity Gain
Output that equals the input. Unity gain screen material reflects as much light as the reference material. Has an even dispersion of light.

Universal Remote
Remote that has the commands of numerous brands stored into memory and can control several different devices simultaneously.

The volume of air that offers the same degree of restoring force on the loudspeaker driver's cone as that of the cone's suspension.

See Video Cassette Recorder.

VCR Plus
VCR feature that, once programmed, allows the user to input the TV guide code for a given program into the VCR, which then automatically sets itself to record that program.

See Port or Passive Radiator.

Vertical Helical Scan (or as JCV calls it, 'Video Home System'). Widely used method of recording audio and video electrical signals onto magnetic tape.

Video Cassette Recorder
Device that records audio and video electrical signals onto magnetic tape (aka videotape recorder).

The unit of electrical potential, or difference in electrical pressure, expressing the difference between two electrical charges.

A unit of power or energy. One horsepower is equal to 745.7 watts.

Windows Media Audio. An audio compression format similar to MP3, but with digital rights management (copy protection and usage restrictions) built-in by Microsoft.

A speaker driver designed to reproduce low frequencies.

Word Length
The sampling rate determines how often an analog wave is sampled; the word length determines the resolution of the sample. The larger the word length, the more accurate the sample as a whole. A 16-bit word length (CD) allows 65,536 different level or volume steps that can be chosen for each sample.

A measurement of speed instability in analog equipment usually applied to cassette transports and turntables. Wow is slow-speed variations, and flutter is fast-speed variations. Lower percentages are better.

One or more rooms powered by one or more amplifiers, which are all fed by one source. A home can be divided into multiple zones, which can play multiple sources, even though several rooms (say, the kitchen, dining room, and living room) all play the same source.