Home Theater Glossary

Five main sound channels plus one low-frequency effects channel. A typical setup uses front left, center, front right and two surrounds. See the 5.1 system layout.

Seven main sound channels plus a low-frequency effects channel. The usual layout adds two rear surrounds to the five main channels of 5.1. See the surround speaker layout.

A panel that absorbs some sound within a room. Its depth and material affect which sounds it can absorb. See the acoustic panel guide.

Materials that change how sound reflects or decays inside a room. Treatment helps room sound; stopping sound from reaching another room calls for other work. See the room treatment guide.

A screen made to let sound pass through it. This lets front speakers sit behind the image. See the screen placement guide.

A speaker with its own power amplifier. It still needs power and a sound signal to play. See the speaker system choices.

A device that raises a sound signal to a level that can drive a passive speaker. Its load limits must suit the speakers. See the receiver and amp guide.

Audio Return Channel sends TV sound back through an HDMI cable to a receiver or soundbar. Both linked ports must support it. See the soundbar connection guide.

The ratio of image width to height. A 16:9 image is 16 units wide for every nine units of height. See the screen dimensions guide.

An audio/video receiver selects sources, processes sound and powers passive speakers. Its HDMI ports also route video to the display. See the AV receiver guide.

Filters and routing that send deep bass to speakers suited to play it, often a subwoofer. This can include bass from main channels as well as LFE. See the subwoofer integration guide.

An absorber built to reduce low-frequency room ringing. A thin wall panel may absorb higher sounds well but do little for deep bass. See the bass trap guide.

Consumer Electronics Control lets linked HDMI devices share commands, such as power or volume. Device settings affect which controls work together. See the system connection guide.

The front sound channel between left and right. It carries much of a film's dialogue, though voices can also appear in other channels. See the front speaker placement.

A distinct stream of sound in a mix. A speaker plays a channel, while a soundbar may use processing to suggest channels without separate boxes. See the soundbar and surround layouts.

A filter that splits sound into frequency bands. In a theater, it can route lower sounds to a subwoofer and higher sounds to main speakers. See the speaker and subwoofer setup.

Decibels of sound pressure level describe sound pressure against a fixed reference. A reading also needs a stated measurement position and weighting to be useful. See the level-setting steps.

A logarithmic measure of a ratio. The reference matters: a volume-control dB value and a measured dB SPL value describe different things. See the system setup guide.

A sound format that can place sounds around and above the listener. Playback needs compatible content and equipment; speaker count alone does not show support. See the Atmos system guide.

Digital signal processing changes sound using calculations. Receivers use it for tasks such as filters and delay as well as EQ. See the receiver features guide.

Enhanced Audio Return Channel carries TV sound to a receiver or soundbar through HDMI. It supports more audio capacity than ARC; both devices must support the desired format. See the Atmos soundbar connections.

Filters that raise or lower parts of the sound spectrum. EQ can change tonal balance, but cannot fix every problem caused by room layout. See the sound tuning sequence.

An early bounce of sound from a nearby wall, floor or ceiling toward the listener. It mixes with direct sound and can affect clarity. See the finding reflection points.

A screen held taut in a rigid frame. It stays in place rather than rolling away after use. See the fixed-frame screen guide.

How often a wave repeats each second, measured in hertz. Low audio frequencies sound like bass; higher ones form treble. See the speaker system basics.

How output level varies across frequency. Read the stated level tolerance with the range; two bare frequency ranges may use different limits. See the reading subwoofer specs.

High-Definition Multimedia Interface carries digital video and audio between devices. A connector's shape alone does not tell you which features the device supports. See the cable and port planning.

Speakers used to create sound from above the listener. Atmos layouts may use ceiling speakers or compatible upward-firing speakers. See the height speaker placement.

The electrical load a speaker presents to an amplifier, measured in ohms. Check the receiver's supported speaker load before connecting a system. See the receiver and speaker matching.

Digital reshaping that makes a tilted projector image look rectangular. Aligning the projector first avoids relying on heavy image correction. See the projector placement guide.

An optical adjustment that moves the image without moving the projector. The allowed shift range depends on the lens and model. See the projector fit checks.

Low-frequency effects is the dedicated bass-effects channel in a surround mix. A subwoofer can also play redirected bass from other channels. See the LFE and subwoofer setup.

The timing match between picture and sound. A delay setting can help align voices with mouth movements when processing puts them out of step. See the final system checks.

The seat or area where you judge and tune the sound. Speaker angles, levels and delay settings depend on where the listener sits. See the choosing the main seat.

A device that turns an electrical audio signal into sound. A speaker cabinet may contain several drivers that share the work across the sound range. See the loudspeaker system guide.

A speaker that needs an external power amplifier. A receiver can supply that power if its speaker outputs suit the load. See the matching passive speakers.

Pulse Code Modulation represents sound as digital samples. A source can decode a soundtrack and send PCM to a compatible receiver. See the receiver format checks.

The fading sound that remains as many reflections build up after the source stops. It differs from a single, distinct echo. See the room reflection guide.

A system that measures sound in a room and adjusts playback settings. Its filters and level changes work alongside good speaker placement. See the room tuning steps.

Reverberation time is the time a sound level takes to fall by 60 dB after the source stops. It varies with frequency and measurement method. See the room decay and bass treatment.

A screen's brightness ratio against a reference surface in a stated direction. Higher gain does not mean every seat gets a brighter image. See the screen gain and seating.

A speaker's sound output for a stated input at a stated distance. Compare specs with the same conditions; sensitivity is not the maximum sound level. See the speaker specification checks.

A long speaker unit that puts several drivers in one enclosure. Some models add a subwoofer, rear speakers or height drivers. See the soundbar layout choices.

Work that limits sound passing between spaces. It can include sealing gaps, adding mass and separating structures; absorbing reflections inside a room serves a different purpose. See the soundproofing guide.

The sound-producing part within a loudspeaker, such as a woofer or tweeter. Different drivers can share the work in different frequency bands. See the speaker system guide.

A group of speakers arranged to play a sound mix. The layout, receiver channels and source format need to work together. See the planning a speaker system.

Two-channel sound, usually played through left and right speakers. A stereo-only source does not contain discrete surround channels. See the stereo receiver guide.

A loudspeaker made for deep bass. It can play LFE and bass sent from other speakers by the system's bass management. See the subwoofer guide.

Speakers beside or behind the listening area that play surround channels. Their positions depend on the selected layout. See the surround placement guide.

The distance from a projector's lens to the screen. Measure from the lens, then check the model's image-size range at that distance. See the projector distance checks.

Lens-to-screen distance divided by image width. It helps check which screen widths a projector can produce from a given position. See the projector room fit.

A speaker driver built for high-frequency sound. A crossover helps keep lower frequencies out of the range it is designed to play. See the speaker driver guide.

A speaker that sends sound toward the ceiling to create a height effect by reflection. Its performance depends on placement and the ceiling. See the upward-firing placement.

This may mean the image's angular width from a seat or how far to the side a display stays useful. Screen makers often state a half-gain viewing limit. See the screen angle and seat distance.

The distance from the viewer's eyes to the screen. It sets the image's angular size and helps you choose a comfortable seat location. See the viewing distance guide.

A loudspeaker driver that handles lower-frequency sound. A woofer may sit inside a main speaker; a subwoofer is built to handle deeper bass. See the woofer and subwoofer guide.

A lens adjustment that changes image size while the projector stays in place. Its range limits the screen sizes available at that throw distance. See the projector zoom and fit.