L
Laser Disc: Now-defunct 12-inch disc format with excellent analog, FM-recorded video image, and either analog or CD-quality PCM-encoded audio. Later discs used one of the analog channels to record an RF-modulated Dolby Digital/AC3 soundtrack and/or used the PCM tracks to encoded a DTS soundtrack.

LCD: Liquid Crystal Display. A display that consists of two polarizing transparent panels and a liquid crystal surface sandwiched in between. Voltage is applied to certain areas, causing the crystal to turn dark. A light source behind the panel transmits through transparent crystals and is mostly blocked by dark crystals.

LCOS: Liquid Crystal on Silicon

Letterbox: Format used widely on laser disc and many DVDs to fit wide-aspect-ratio movies (1.85:1 and 2.35:1, for example) into a smaller frame, such as the 1.78:1 area of an anamorphic DVD or the 1.33:1 area of a laser disc or video tape. The image is shrunk to fit the screen, leaving blank space on the top and bottom. This process sacrifices some vertical detail that must be used to record the black bars.

LFE: Low Frequency Effects track. The .1 channel of a Dolby Digital, DTS, or SDDS soundtrack. The LFE is strictly low-frequency information (20 to 120 Hz, with 115 dB of dynamic range) that's added to the soundtrack for extra effect. This track does not inherently contain all the bass of the soundtrack.

Line-Level (Low-Level): A level of electrical signals too low to make the average speaker move sufficiently. Amplifiers receive line-level signals and amplify them to speaker level.

LNB: Low-Noise Blocker. The receiving end of a satellite dish.

Low Pass: A filter that lets low frequencies go through but doesn't let high frequencies go through. Same as high cut.

Luminance: The black and white (Y) portion of a composite, Y/C, or Y/Pb/Pr video signal. The luminance channel carries the detail of a video signal. The color channel is laid on top of the luminance signal when creating a picture. Having a separate luminance channel ensures compatibility with black-and-white televisions.

M
Megachanger: CD or DVD player with massive disc storage capacity, holding 50 or more discs.

MHz: Megahertz, or 1 million Hz.

Midbass: The middle of the bass part of the frequency range, from approximately 50 to 100 Hz (upper bass would be from 100 to 200 Hz). Also used as a term for loudspeaker drivers designed to reproduce both bass and midrange frequencies.

Midrange: The middle of the audio frequency range. Also used as a term for loudspeaker drivers designed to reproduce this range.

MLP: Meridian Lossless Packing. Encoding format that is able to completely reconstruct the original signal at the receiving end. No information is lost or discarded, regardless of how trivial it might be. Used to encode six channels of high-resolution audio on DVD-A.

Mono: Monophonic sound. One channel.

MP3: MPEG-1 Audio Layer-3. Compression scheme used to transfer audio files via the Internet and store in portable players and digital audio servers.

Multiple-Rate Encoding: Instead of locking encoding at a certain constant data rate, it allows the codec to choose whatever rate is best for that portion of the recording. Usually reduces file size with proportionally less loss in quality.

Multisource: System with multiple sources. Can also be used to describe a receiver that can provide multiple different sources into different rooms.

Multiroom: System that provides audio or video to multiple areas. Usually with only one source.

Multizone: System that provides different sources into multiple areas simultaneously.

N
Negative Gain Screen: Material that reflects less light than a reference material. Often used for DLP and LCD projection systems.

Noise: An unwanted portion of a signal such as hiss, hum, whine, static, or buzzing.

NTSC: National Television Standards Committee. Government-directed committee that established the U.S. color TV standard in 1953. Also known, sarcastically, as Never Twice the Same Color or Never The Same Color due to the inherent difficulty in achieving proper color calibration.

O
Octave: The difference between two frequencies where one is twice the other. For example, 200 Hz is an octave higher than 100 Hz. 400 Hz is one octave higher than 200 hz.

Ohm: A measure of how much something resists (impedes) the flow of electricity. Larger numbers mean more resistance.

Optical Digital Cable: Fiber optic cable that transfers digital audio signals as light pulses.

P
Passive: Not active. A passive crossover uses no external power and results in insertion loss. A passive speaker is one without internal amplification.

Passive Radiator: A radiating surface (usually similar to a conventional speaker cone) that is not electrically driven but shares the same air space in a sealed cabinet with an electrically driven loudspeaker. This arrangement is functionally similar to a loudspeaker with a vented (ported) cabinet, with the passive radiator serving the duties of the air in the port.

Parametric: Equalizer with adjust-able parameters, such as center frequency and bandwidth (Q), as well as amplitude.

PCM: See Pulse Code Modulation.

Phase: Time relationship between signals; it's all relative.

Piezo: A type of speaker driver that creates sound when a quartz crystal receives electrical energy.

Pixel: Contraction of picture element. The smallest element of data in a video image.

Plasma: Flat-panel display technology that ignites small pockets of gas to light phosphors.

Port: An aperture in a loudspeaker enclosure that helps extend the usable low-frequency output. A ported enclosure is also called vented or bass reflex.

Power Amp: See Amplifier.

Power Output: A measure, usually in watts, of how much energy is modulated by a component.

Preamplifier: A control and switching component that may include equalization functions. The preamp comes in the signal chain before the amplifiers.

Pre Outs: Connectors that provide a line-level output of the internal preamp or surround processor.

Pre Outs/Main Ins: Connectors on a receiver that provide an interruptible signal loop between the output of the internal preamp or surround processor portion of the receiver and the input of the amplifier portion of the receiver.

Processors: Anything that processes an incoming signal in some way. Surround processors, for example, can decode a Dolby Digital signal to send to an amp so you can hear it.

Progressive Scanning: Each frame of a video image is scanned complete, from top to bottom, not interlaced. For example, 480p means that each image frame is made of 480 horizontal lines drawn vertically. Computer images are all progressively scanned. Requires more bandwidth (twice as much vertical information) and a faster horizontal scan frequency than interlaced images of the same resolution.

Projection System: Display that projects image onto a screen.

Pulse Code Modulation: (PCM) a way to convert sound or analog information to binary information (0s and 1s) by taking samples of the sound and record the resulting number as binary information. Used on all CDs, DVD-Audio, and just about every other digital audio format. It can sometimes be found on DVD-Video.

PVR: Personal Video Recorder. Marketing term for Video HDRs such as TIVO.

Q
Q: The magnification or resonance factor of any resonant device or circuit. Also the width of affected frequencies in an equalizer. Shaped somewhat like an adjustable width bell curve.