Home Theater Technical Reference

24p judder is the uneven or choppy motion you see when 24 frame-per-second film is shown on a display whose refresh rate is not a multiple of 24. On a 60 Hz display, 3:2 pulldown holds frames for 2 and 3 refreshes alternately (33.3 ms and 50 ms), and a 120 Hz panel fixes the cadence with 5:5 pulldown (5 x 8.3 ms = 41.7 ms). Fast-responding OLEDs still look stuttery on slow pans because each frame is held, not blurred.

4K@120 refers to video output at 3840x2160 resolution running at a 120Hz refresh rate, a combination introduced as part of the HDMI 2.1 specification. Carrying this signal at full quality requires substantial HDMI bandwidth, and how much of that bandwidth a given device actually provides determines whether the picture arrives at full 4:4:4 chroma or a reduced subsampled format.

An acoustically transparent screen is a projection surface made from a woven or micro-perforated material so that speakers can sit behind it and sound passes through. The cost is a high-frequency loss: Elite Screens rates its AcousticPro UHD weave at -2.36 dB mean attenuation from 8 to 20 kHz, while an independent 2016 test measured 1 to 7 dB of treble loss at 20 kHz across common weaves. Texture can cause moiré, so the weave should be tested at your projector's resolution and viewing distance.

An ALR (Ambient Light Rejecting) screen is a projection screen with a microstructured or layered surface that selectively reflects the projector's own light back toward viewers while absorbing or redirecting light arriving from other angles, such as room lighting or windows. Unlike a standard matte white screen, which diffuses all incoming light uniformly in every direction, an ALR screen relies on an angular reflective principle to preserve image contrast under ambient light. Performance depends heavily on the direction the ambient light comes from relative to the projector.

ANSI contrast is a contrast ratio measurement using a 16-square checkerboard pattern with alternating black and white squares displayed simultaneously. Unlike manufacturer on/off contrast specs (which measure full-screen white versus full-screen black), ANSI averages brightness across all white and black squares in a single frame, typically yielding ratios of 200–600:1 rather than the thousands-to-one figures advertised.

ANSI lumens is a standardized brightness measurement for projectors developed by the American National Standards Institute, calculated by averaging light output readings taken at nine points across a 100% white projected image arranged in a 3x3 grid. Because it measures the full image rather than a single spot, and uses a full-white test pattern, it is widely treated as a more reliable brightness figure than manufacturer-quoted light-source or LED lumen specs.

Anti-reflective (AR) coatings use thin-film interference to cancel reflected light, reducing reflectance from 8% to below 0.5% while preserving sharp imagery and black depth. Anti-glare (AG) coatings scatter reflections through microscopic surface texturing, reducing glare intensity at the cost of image clarity and black depth degradation.

Automatic Brightness Limiter (ABL) is a power-management circuit in OLED displays that reduces peak brightness when Average Picture Level (the proportion of bright pixels on screen) is high. ABL protects the panel from thermal runaway, power-delivery failure, and accelerated emitter degradation; it is a circuit-level protection not intended to be user-disabled, and manufacturers do not provide a menu option to turn it off.

Black Frame Insertion is a motion-clarity technique that inserts brief dark frames between lit ones — or strobes the LCD backlight — to shorten how long each frame is visible to the eye. The goal is to emulate the impulse-driven behavior of CRT displays, where each frame illuminates briefly and then goes dark, reducing the persistence-based smear that sample-and-hold panels otherwise produce.

Black frame insertion (BFI) for gaming is a display mode that blanks the screen or backlight for part of every refresh so each frame is visible for a few milliseconds instead of the full refresh period, cutting sample-and-hold motion blur. A 120 Hz panel with a 38% duty cycle shows each frame for about 3.2 ms instead of 8.3 ms, at the cost of brightness, added flicker, and usually variable refresh rate.

Bit depth is the number of bits used to encode each color component of a pixel: 8-bit gives 256 levels per channel (16,777,216 colors), 10-bit gives 1,024 (1,073,741,824), and 12-bit gives 4,096 (68,719,476,736). ITU-R BT.2100 allows HDR video at 10 or 12 bits per component. More bits mean smaller steps in a gradient, which keeps HDR skies, fog, and shadow falloff from breaking into visible bands.

Black crush is the loss of near-black detail, where dark steps just above reference black are displayed as pure black. It comes from a Brightness (black level) control set too low, a gamma or EOTF curve too steep near black, source or player clipping below video level 16, or an OLED's near-black drive behavior. A PLUGE pattern with bars at -4%, -2%, +2% and +4% finds it in about 30 seconds.

Blooming is the halo of unwanted light that appears around a small bright object on a dark background on a local-dimming LCD, because the whole backlight zone behind it must light up. A 4K panel has 8,294,400 pixels, so even a 2,584-zone mini-LED set puts about 3,210 pixels in each zone. OLED has no backlight and cannot bloom, and the more and smaller the zones, the smaller the halo.

BT.2020 is the ITU-R standard that defines the system colorimetry for ultra-high-definition television, specifying a wide-color-gamut RGB primary set covering about 75.8% of the CIE 1931 chromaticity area. In practice, virtually all current HDR content is color-graded inside a P3-D65 sub-gamut and carried in the BT.2020 container, because no consumer mastering monitor or TV can faithfully reproduce true BT.2020 primaries.

Chroma subsampling is a bandwidth-saving technique that retains full per-pixel luminance resolution while encoding the two chrominance components at lower spatial resolution. The J:a:b notation describes a J-pixel-wide by 2-pixel-tall sample window where J is the luma reference, 'a' is the count of chroma samples in the first row, and 'b' is the number of chroma sample changes between rows. Every consumer video delivery format — UHD Blu-ray, broadcast, cable, and streaming services like Netflix, Disney+, and Apple TV+ — ships at 4:2:0.

Color banding is the visible stepping in a smooth gradient, such as a sky or a fade to black, where neighboring shades collapse into flat stripes with hard edges instead of blending. It is also called posterization. It appears when the signal, the panel, or the TV's processing cannot represent enough distinct levels: 8-bit video has 256 levels per channel against 1,024 for 10-bit, and RTINGS finds that panel bit depth alone does not predict how smooth a TV looks.

Color filtering and color conversion are the two ways a display turns one light source into red, green, and blue. A filter absorbs the wavelengths it does not want; a quantum-dot conversion layer re-emits blue light as red or green instead. Wikipedia puts the filter penalty at "filtering out 2/3 of passing light" in LCDs, which is why QD-OLED, built on a blue emitter and no color filter, measured about 1,110 nits sustained against 743 nits for a 2022 WOLED.

Color gamut coverage is a percentage measurement comparing the area of a display's reproducible colors (as plotted on the CIE 1931 chromaticity diagram) against the area of a reference color standard like DCI-P3 or BT.2020. It measures hue and saturation reach in 2D, excluding luminance (brightness).

D65 is the CIE standard daylight illuminant (approximately 6500K) specified as the reference white point by broadcast and display standards including ITU Rec. 709, BT.2020, and sRGB. It represents average midday daylight and serves as the target for consistent, neutral white rendering across video production, mastering, and consumer display environments.

Color gamut is a 2D construct — the area of chromaticity coordinates a display can reproduce, drawn as a triangle on the CIE 1931 diagram with luminance ignored. Color volume extends that into a 3D solid by adding luminance, describing which colors are reproducible at every brightness level rather than only at one reference luminance. For HDR, where colors must hold at high luminance, the 3D figure is the more meaningful number.

A color wheel is the spinning, segmented filter disc in a single-chip DLP projector that turns white light into a rapid sequence of red, green, and blue fields for one micromirror chip. A 2x wheel turns at 7,200 RPM (120 revolutions per second) and a six-segment RGBRGB wheel repeats each primary four times per 60 Hz frame. The sequential color is why some viewers see the rainbow effect.

DCI-P3 is the wide-gamut RGB color space released in 2005 by Digital Cinema Initiatives, LLC for theatrical digital projection and formalized in SMPTE RP 431-2. It is larger than BT.709/sRGB but smaller than ITU-R BT.2020. On consumer TV and monitor spec sheets, 'DCI-P3' almost always means P3-D65 — the same P3 primaries with a D65 white point rather than the green-tinted ~6300 K cinema white.

Delta E (ΔE) is a numerical measure of the distance between two colors in a defined color space, most commonly CIELAB. CIEDE2000 (dE2000) is the most refined version of this formula, adding perceptual weighting so the calculated distance better matches how humans actually perceive color differences.

A deuterium-substituted organic emitter used in WOLED panels to extend blue subpixel operational life by reducing bond-cleavage degradation under electrical stress. Replacing hydrogen atoms with deuterium (a heavier, stable hydrogen isotope) lowers molecular vibration frequencies, slowing the chemical breakdown pathways that cause accelerated blue pixel fading in conventional OLED displays.

Dirty screen effect (DSE) is a high-frequency unevenness in a TV's image, seen as blotchy darker patches or smears across the middle of the screen when a flat color fills the picture, most often on LCD panels. RTINGS measures it from a photo of 50% and 5% gray fields run through a high-pass filter, and treats under 0.15% at 50% gray and under 0.1% at 5% gray as good. It is separate from vignetting, which is darkened edges and corners.

Frame Rate Control (FRC), also called temporal dithering, makes a panel show a shade it cannot natively produce by flipping each pixel between two neighboring levels over successive frames. An 8-bit panel with 2-bit FRC (8b+2) simulates 10-bit's 1,024 levels per channel and 1.07 billion colors. VESA DisplayHDR accepts 8-bit plus 2-bit dithering as the minimum driver depth at every tier, so a "10-bit" label does not mean a native 10-bit panel.

DLP (Digital Light Processing) is a projection technology that uses millions of microscopic mirrors on a chip called a Digital Micromirror Device (DMD) to create images. Each mirror tilts thousands of times per frame to control pixel brightness and color through duty-cycle modulation. Originally developed by Texas Instruments in 1987, DLP is now prevalent in cinema projection, home theater projectors, and portable displays.

Dolby Vision Gaming is Dolby's dynamic-metadata HDR mode for games, launched on Xbox Series X|S on September 28, 2021 with more than 100 optimized titles. It runs over the Dolby Vision low-latency HDMI mode, where the console does the tone-mapping work and sends 12-bit 4:2:2 video, and it works with ALLM and VRR on TVs that support it. As of the sources I could load, PlayStation 5 does not offer it.

Dolby Vision IQ is an enhancement to standard Dolby Vision that uses a TV's ambient light sensor to automatically adjust picture settings based on room lighting conditions. The technology adjusts tone mapping and brightness in real time to preserve detail and contrast across varying lighting environments.

A dual-cell LCD stacks a lower-resolution monochrome LCD (typically 1,920 x 1,080) behind the 4K color LCD and uses it as a per-pixel light gate, so the backlight is blocked twice. Hisense's U9DG measured a 0.005 cd/m2 black level and 1,119 nits sustained on a 20% window, and drew about 315 watts. That black matches the 0.005 cd/m2 ceiling ITU-R BT.2100 sets for a reference display.

A dual-mode gaming panel is a monitor that presents two video modes from one panel, usually 4K at 240 Hz or full HD (1920 x 1080) at 480 Hz, by reporting a second EDID and grouping each 2 x 2 block of physical pixels into one logical pixel. The LG 32GS95UE does it at 32 inches on OLED, takes about 5 seconds to switch, and needs DSC for full speed on its DisplayPort 1.4 and HDMI 2.1 inputs.

EOTF Tracking measures how accurately a display's brightness output follows the mandated Electro-Optical Transfer Function (EOTF) curve—such as PQ/SMPTE 2084 for HDR—across the entire brightness range from black to peak white. Poor EOTF tracking causes shadow detail loss (black crush), washed-out midtones, or blown-out highlights, even on displays with strong peak brightness specifications.

Filmmaker Mode is a TV picture preset defined by the UHD Alliance and intended to preserve the creative intent of the filmmaker when content is viewed in the home. It disables post-processing features such as motion smoothing, sharpening, and noise reduction, and preserves the source content's original aspect ratio, colors, and frame rate.

A foot-lambert (fL, ftL) is a US unit of luminance equal to 1/π candela per square foot, or 3.426 cd/m² (nits). Cinema screen brightness is specified in it: SMPTE ST 431-1 sets 14.0 fL (48 cd/m²) at the center of a digital cinema screen, and Infinity Vision, Dolby Cinema and other premium large formats are described in fL against that 14 fL baseline. Projector buyers use it to turn a lumens rating and a screen size into a real picture brightness.

Full-Array Local Dimming (FALD) is a backlight technology that distributes LEDs across the entire surface of an LCD panel, grouped into independently controllable zones to enable targeted brightness control. Unlike edge-lit displays, which place LEDs only along screen borders, FALD allows dimming of zones corresponding to dark areas while brightening zones under bright content, resulting in higher contrast and deeper apparent black levels compared to traditional LED backlighting.

Game Mode is a TV or projector picture preset that bypasses most video post-processing (motion interpolation, noise reduction, dynamic contrast) to cut input lag. The HDMI Forum's Auto Low Latency Mode (ALLM, part of HDMI 2.1) lets a console or PC switch the display into it automatically. Current flagship TVs measure about 9 to 13 ms in it, against 60 to 120 ms or worse with motion smoothing left on.

Gamma is the non-linear power-law relationship between input signal voltage and output brightness in a display. Modern displays require gamma correction to properly render source content that was encoded for legacy CRT behavior. Gamma 2.2 suits bright-room viewing, while gamma 2.4 and the BT.1886 standard are optimized for dark viewing environments.

Gray-to-gray (GtG) response time is the duration a pixel takes to transition from one brightness level to another. Measured in milliseconds according to industry methodology using a 10%–90% luminance threshold, it determines how quickly pixels can keep pace with frame-by-frame image changes, affecting motion clarity in games and fast-moving content.

A brightness window is the white rectangle, sized as a percentage of screen area (commonly 1%, 2%, 3%, 10%, 25%, 50% or 100%), that reviewers and standards bodies display to measure HDR luminance. A TV's peak nits are quoted on a small window and fall as the window grows: the LG C6 measures 1,355 nits at 10% but 236 nits at 100%, a 5.7 to 1 drop. The window size, not the headline number alone, tells you what a TV can do in a bright scene.

Image retention is a temporary afterimage that lingers briefly on a display after static content is removed, and it typically fades on its own or after a panel compensation cycle. Burn-in is permanent, uneven subpixel degradation from sustained uneven use, and it does not reverse. The two are frequently confused because both start from the same underlying cause: uneven pixel wear.

Input lag is the delay between a video signal arriving at a display and that picture actually appearing on screen, measured separately from pixel response time. It is a system-level processing delay, tested with tools that flash a signal and time how long the display takes to begin rendering it.

Keystone correction is an electronic pre-warp that reshapes the trapezoid a projector throws when it is not square to the screen back into a rectangle. It costs resolution and brightness because the corrected side is compressed onto fewer pixels, which is why Epson, JVC and Sony put lens shift (Epson 5050UB: plus or minus 96.3% vertical) on premium models and leave digital keystone as the fallback.

A laser-based projection light engine that uses a blue laser diode to excite a spinning phosphor wheel, which converts light into red, green, and blue components for display. Laser phosphor is the mainstream laser implementation in projectors, offering 20,000–30,000 hours of operational lifespan, roughly double the efficiency of traditional lamp projectors, and zero lamp-replacement maintenance.

LCoS (Liquid Crystal on Silicon) is a reflective imaging technology in which a liquid crystal layer sits on a mirrored silicon chip that carries the pixel circuitry behind the reflective surface. JVC brands it D-ILA and Sony brands it SXRD. The JVC DLA-NZ8 lists 80,000:1 native contrast from three 0.69-inch 4K chips, the highest native figure among consumer projector technologies.

Lens shift physically slides a projector's lens up, down or sideways inside the housing to move the image on the screen without tilting the projector, so the picture keeps full resolution, brightness and focus uniformity. It is quoted as a percentage of image height or width: the Epson Home Cinema 5050UB lists plus or minus 96.3% vertical and 47.1% horizontal, the JVC DLA-NZ8 plus or minus 80% and 34%, and the Sony VPL-XW5000ES plus or minus 71% and 25%.

A local dimming zone is an independently controlled backlight segment in a Full-Array Local Dimming (FALD) or Mini LED TV that can be dimmed or turned off to enhance contrast in HDR content. Standard FALD TVs typically feature 20–300 zones, while Mini LED TVs range from under 300 to 14,000+ zones depending on price tier and screen size. Higher zone density reduces visible blooming (halo effects) around bright objects on dark backgrounds.

Logo dimming automatically detects static on-screen elements that remain in the same position and reduces their brightness to prevent pixel degradation. By decreasing luminance in affected areas, the feature slows differential aging and helps mitigate burn-in risk under high-risk viewing scenarios (8+ hours daily of static content). Implementation and timing thresholds vary by manufacturer.

Match Frame Rate is a streaming-box setting that switches the HDMI output refresh rate to the frame rate of the title being played, so 24 fps film plays at 24Hz (or 23.976Hz) instead of being converted to 60Hz. Apple TV matches 60, 50, 30, 25, and 24 fps content with a region-appropriate rate, Roku calls it auto-adjust display refresh rate, and Fire TV and Google TV have equivalents. The payoff is the end of 3:2 pulldown judder; the cost is a brief blank screen at each switch.

A self-emissive display technology using microscopic inorganic LEDs (under 100 micrometers) as individual pixels that emit light independently without requiring a backlight. Micro LED achieves higher brightness and longer lifespan than OLED but remains primarily in commercial and high-end consumer markets as of 2026.

Micro RGB is the 2026 marketing name Samsung (R95H, R85H) and LG (Micro RGB evo MRGB95B) use for an LCD TV lit by thousands of controlled red, green and blue LEDs, each under 100 micrometers in Samsung's case, instead of a white or blue backlight filtered through quantum dots. It is still an LCD with zoned local dimming, not a self-emissive Micro LED display. Samsung claims 100% BT.2020 coverage (VDE-verified), while a 65-inch R95H measured 93.3% BT.2020 and 2,039 nits at a 10% window in Filmmaker Mode.

Mini LED backlight refers to an LCD TV backlight built from LEDs substantially smaller than those used in conventional LED-LCD TVs, packed at much higher density behind the panel. The smaller chip size lets manufacturers fit far more LEDs into the same backlight area, which allows the screen to be divided into many more independently controlled local-dimming zones. It is a backlight technology for LCD panels, not a self-emissive display technology.

MLA is a microscopic lens layer added on top of WOLED pixels that redirects light emitted at oblique angles back toward the viewer. It raises peak HDR brightness by roughly 60 to 70 percent over a non-MLA panel of the same OLED chemistry, without changing the underlying emitter material or driving scheme.

Motion interpolation is TV video processing that synthesizes new frames between the source's real frames, using motion estimation and compensation (MEMC), to make motion look smoother. Applied to 24 fps film it produces the soap opera effect, which is why Filmmaker Mode turns it off. Brand names include LG TruMotion, Samsung Auto Motion Plus (Picture Clarity) and Sony Motionflow, and the processing typically adds about 10 ms of input lag.

Moving Picture Response Time (MPRT) measures how long a pixel remains visible on screen during motion, not how quickly pixels change color. MPRT is determined primarily by refresh rate—lower refresh rates result in longer pixel persistence and more motion blur—and can be reduced through strobing or rapid pixel shuttering without increasing refresh rate.

Native contrast ratio is the ratio of the brightest white to the darkest black a display can produce simultaneously on the same screen, measured using standardized luminance test patterns. It reflects the panel's inherent capability independent of local dimming or dynamic adjustments, and is distinct from inflated dynamic contrast claims that measure white and black in isolation.

Neo QLED is Samsung's name for its quantum-dot LCD TVs with a Mini LED backlight and local dimming, in 2026 the QN80H (55 to 100 inches), QN70H and the 8K QN990H. It is an LCD, not an OLED: choose.tv counted 110 dimming zones on a 65-inch QN80H and measured 92.7% DCI-P3. Plain QLED is Samsung's label for quantum-dot LCDs generally; Neo QLED adds the Mini LED backlight, and Micro RGB replaces it with RGB LEDs.

A nit is one candela per square meter (cd/m²), the common unit for measuring luminance—the brightness of light emitted or reflected from a display surface per unit area. cd/m² is the SI-derived unit; nit is the widely-used industry term for the same measurement.

Peak brightness is the maximum luminance a display can produce, expressed in nits (candela per square meter, cd/m2), typically measured over a small percentage of the screen (a 2% or 10% "window") rather than across the full panel. It is the primary metric used to describe how bright HDR highlights — specular reflections, explosions, the sun — can get on a given display.

PHOLED (Phosphorescent Organic Light-Emitting Diode) is an OLED emitter technology that converts both singlet and triplet excitons into light using heavy-metal complexes, achieving approximately 100% internal quantum efficiency compared to ~25% for conventional fluorescent OLEDs. As of 2025, red and green subpixels in shipping OLED TVs employ phosphorescent emitters, while blue phosphorescence remains in development for consumer applications.

Pixel Refresher is LG's name for the OLED maintenance routine that measures pixel deterioration, including TFT voltage changes while the TV is off, and compensates for it, clearing temporary image retention. LG runs it automatically after every 4 hours of cumulative viewing and for about 1 hour after 2,000 hours; Sony's Panel Refresh is manual, about 1 hour, and limited to once a year. It does not reverse permanent burn-in.

Pixel shifting is a technique where an imaging chip displays multiple sub-frames in rapid succession, with each sub-frame slightly offset, to create the illusion of higher resolution on screen than the native chip natively supports. DLP, Epson 3-LCD, and JVC projectors use this method to meet the CTA's 8.3-million-pixel definition of 4K UHD without requiring expensive native 4K imaging chips.

Primary RGB Tandem is LG Display's TV OLED panel architecture that stacks separate red, green and blue emission layers (the 2025 version uses red, green and two blue) in place of the older yellow-plus-two-blue stack. The 2026 generation, Primary RGB Tandem 2.0, is rated by LG Display at up to 4,500 nits and 99.5% DCI-P3, up from a 4,000-nit rating in 2025. Reviewers measure far less: 2,213 nits on the 2025 LG G5 and just over 3,400 nits on a 2% window for the 2026 G6.

PSSR (PlayStation Spectral Super Resolution) is the AI upscaling library on the PS5 Pro. It analyzes each game frame pixel by pixel to reconstruct a 4K image from a lower internal resolution, such as 1080p or 1440p. An upgraded version built on Sony's Project Amethyst work with AMD, shared with FSR 4, began rolling out February 27, 2026 and reached existing games through a March 16, 2026 system update.

QD-OLED is an OLED panel architecture that uses a blue OLED emission layer combined with quantum-dot color-conversion films for red and green, instead of the white OLED plus color-filter approach used by traditional WOLED. The conversion approach produces wider color volume and higher saturation at full luminance than WOLED of the same generation.

QD-OLED triangular subpixel layout is Samsung Display's proprietary arrangement of red, green, and blue subpixels on QD-OLED panels, with the green subpixel positioned above the red and blue subpixels rather than in an even side-by-side stripe. It is a three-subpixel (RGB) design rather than the four-subpixel RWBG structure used on LG Display's WOLED panels. First-generation QD-OLED panels use diamond-shaped subpixels in this triangular arrangement, which Samsung Display has since begun replacing with a vertically aligned "V-Stripe" layout on newer panels.

QNED is LG's marketing name for its premium LCD TV line, in 2026 the QNED evo Mini LED series (QNED90 down to QNED70, up to 115 inches). These are LED-backlit LCDs with Mini LED local dimming, 120 Hz native panels and a claimed 100% color volume (DCI-P3), not self-emissive displays. The name echoes a research term, quantum nano-emitting diode, that LG's TVs do not use, and its color claim is DCI-P3 volume, narrower than BT.2020.

Quantum dot color conversion is a display technique in which nanoscale semiconductor particles absorb blue light and re-emit it as narrow-spectrum red or green light through photoluminescence. It is used to enhance the color output of blue-LED-backlit LCD TVs and to generate color in QD-OLED panels, replacing or supplementing conventional pigment-based color filters. The particle's physical size determines the emitted color, with larger dots emitting redder light and smaller dots emitting light closer to violet.

A visual artifact in single-chip DLP projectors where rapid eye movements cause viewers to perceive separated red, green, and blue colors as distinct outlines or shadows trailing moving objects. The effect results from the sequential color presentation inherent to single-chip DLP technology, and its visibility varies significantly among individual viewers.

Rec. 709 is the ITU-R color standard that defines RGB primaries, white point, and transfer functions for HD video (1920×1080). It serves as the baseline color space for SDR content across broadcast, streaming, Blu-ray, and professional video production, with a maximum luminance of approximately 100 cd/m² and color gamut coverage of 35.9% of the CIE 1931 color space.

An RGB Mini LED backlight replaces a conventional Mini LED TV's array of white or blue LEDs with individually controlled red, green, and blue diodes within each LED, removing the need for a separate quantum-dot color-filter layer. Manufacturers including Hisense and Sony market this as delivering wider color volume and fewer halo/blooming artifacts than standard Mini LED backlighting.

An RGB triple-laser projector generates light with three separate red, green and blue laser diodes instead of one blue laser exciting a phosphor, so each primary is spectrally pure. Christie rates its RGB pure laser cinema line at approximately 98% of Rec. 2020 against Rec. 709 for laser phosphor, with 15,750 to 50,000 lumens. Home models such as the Samsung Premiere LSP9T and Hisense PX3-Pro claim 106% and 110% of BT.2020.

Screen gain is a measurement of a projection screen's reflectivity, expressed as a ratio of light reflected from the screen compared to light reflected from a standard matte-white magnesium oxide reference board. A gain of 1.0 (unity gain) reflects the same amount of light as the reference; higher gains concentrate reflected light toward the center viewing axis, increasing brightness but narrowing the viewing cone.

SMPTE and THX are two competing horizontal viewing-angle guidelines used to calculate ideal seating distance from a screen: SMPTE's cinema-derived figure of 30 degrees produces a more conservative seating distance (about 1.63x screen diagonal for 16:9), while THX's figures — most often cited as 36 degrees for optimum immersion — place viewers noticeably closer to the screen. Both describe the angle formed at the viewer's eye by the screen's horizontal width, but they optimize for different goals: SMPTE for accurate, full-frame perception; THX for maximum immersion.

Tone mapping is the process of converting HDR video signals to match a display's brightness and color capabilities. Source-side tone mapping occurs at the video source (like a streaming device or console) using display capability data, while display-side tone mapping happens inside the TV itself. The choice between them affects highlight preservation, shadow detail, and color accuracy.

Subpixel dimming is the plain-language name for what an OLED does: every pixel, and every red, green, blue or white subpixel inside it, is lit and dimmed individually, so black is made by switching emitters off. It is not a standardized spec; LG and Hisense market the same idea as Pixel Dimming. A 4K OLED has 8,294,400 independently controlled pixels, which TFTCentral equates to 8.3 million dimming zones, against a few thousand on a mini-LED LCD.

Tandem OLED is a stacked-emitter OLED panel architecture in which red, green, and blue emission layers are vertically laminated within a single panel, distributing drive current across multiple emission stacks rather than overdriving a single one. LG Display's TV implementation, formally branded Tandem WOLED, debuted on the 2025 LG G5 and Panasonic Z95B as Primary RGB Tandem and was upgraded to Primary RGB Tandem 2.0 on the 2026 LG G6, W6, and the 77-inch and 83-inch C6H sizes. Panel-spec peak brightness claims (4,000 nits in 2025; 4,500 nits in 2026) describe the panel's theoretical maximum, not the calibrated TV-mode output reviewers measure, which lands at roughly half the panel-spec figure.

Throw ratio is the distance from a projector's lens to the screen divided by the width of the image it fills (R = D / W). A ratio of 2.0 puts the projector 2 feet from the screen for every 1 foot of image width, and ratios of 0.4 or less are called short throw. The Epson Home Cinema 5050UB zooms from 1.35 to 2.84 and the Samsung Premiere LSP9T sits at 0.189. Multiply the ratio by screen width for distance: a 120-inch 16:9 screen is 8.72 feet wide, so the Epson reaches it from 11.8 to 24.8 feet.

Tone mapping is the process of fitting an HDR master's luminance range into the actual brightness, black-level, and color-volume capability of the output device. ITU-R BT.2390 defines the reference behavior for HDR-to-HDR display mapping and BT.2408 covers HDR-to-SDR conversion guidance, while HGiG specifies a game-side variant that pre-maps the signal so the display can pass it through.

TV auto-calibration is a workflow in which calibration software drives a TV's own picture controls over the network while a colorimeter measures the screen, so grayscale and color are corrected automatically instead of by hand. The main implementation is Portrait Displays' Calman AutoCal, built into Calman Ready sets from LG, Samsung, Sony, Hisense, and TCL. It still needs a Calman license, a compatible meter, and usually a pattern generator, and it corrects color accuracy only, not uniformity or peak brightness.

An ultra short throw (UST) projector is a projector designed to sit just inches to a couple of feet from its screen and still fill it with a large image, using a throw ratio below roughly 0.4:1 (industry figure) to 0.25-0.5:1 (manufacturer-cited range). It typically sits in a low console beneath the screen rather than being ceiling-mounted, and is commonly paired with a specialized ambient-light-rejecting (ALR) screen built for its steep projection angle.

Off-axis color shift occurs when a display's color accuracy, brightness, and contrast degrade as the viewer moves away from the screen's center line. The degradation varies significantly by panel type—VA panels show noticeable color distortion and contrast loss beyond 25–30 degrees off-center, while IPS and OLED panels maintain consistent color and brightness across wider viewing angles, making them more suitable for multi-seat home theater arrangements.

VRR flicker (gamma flicker) is a brightness and gamma shift that occurs when a display's refresh rate adjusts during Variable Refresh Rate operation, most noticeable in dark scenes where OLED subpixels become misaligned with their gamma optimization curve. All tested OLED gaming monitors exhibit this effect to varying degrees, though it can be mitigated through frame-rate capping or anti-flicker display features.

WOLED is the OLED TV panel architecture in which white-emitting OLED layers sit behind red, green and blue color filters, plus an unfiltered white subpixel that adds brightness. LG Display is its main maker and supplies it to LG, Panasonic, Philips, Hisense and others. LG Display's fourth-generation WOLED, a four-stack Primary RGB Tandem design, is rated at 4,000 nits peak white and 2,100 nits of color brightness.

The WOLED saturated-color brightness deficit is the gap between how bright a WOLED OLED panel can render white/near-white content versus fully saturated colors (red, green, blue), caused by the panel's extra unfiltered white subpixel contributing little to saturated-color output. Measurements from TFTCentral show saturated-color output on a WOLED panel reaching only around 40% of the level an equivalent QD-OLED panel produces, which lacks a white subpixel and produces color additively from its red, green, and blue subpixels.

WRGB is the four-subpixel design used in LG Display's WOLED panels: each pixel adds a fourth, unfiltered white subpixel alongside the standard red, green, and blue subpixels. The white subpixel is physically larger than the color subpixels and exists specifically to boost brightness and efficiency beyond what an RGB-only OLED structure could reach.

Speaker impedance directly affects the power an amplifier must deliver: halving impedance from 8 ohms to 4 ohms requires double the current at the same voltage, theoretically doubling power output. Real amplifiers fall short of this 2:1 ratio due to power-supply voltage sag and current-delivery limits, and power specifications are only comparable when measured at identical impedance and test conditions.

In Dolby's notation the three numbers are ear-level speakers, subwoofers and height speakers, so 5.1.2 is 7 speakers plus a sub, 5.1.4 is 9, and 7.1.4 is 11. The Dolby reference for the overhead pairs is a 45 degree elevation (30 to 55 degrees allowed). Each step needs more amplifier channels: 7.1.4 takes 11, which is why a 9-amp receiver such as the Denon AVR-X3800H needs outside amplification to drive it.

An all-channels-driven (ACD) power rating is the continuous per-channel power an amplifier can deliver while every channel is driven into its rated load at the same time, for the full rated bandwidth and distortion. It is almost always lower than the headline 1-channel- or 2-channel-driven number, because that number is measured with the unused channels idle.

Amplifier clipping is distortion that happens when an amplifier is asked for more output voltage or current than its power supply and output stage can deliver, so the waveform peaks are flattened. A hard-clipped sine approaches a square wave, which carries twice the average power of the sine at the same peak (+3 dB) and strong high-frequency harmonics, so clipping can overheat a tweeter at a volume that a clean signal of the same peak would not. The FTC rule defines rated power at no more than 1.0% THD+N.

An AMT (Air Motion Transformer) tweeter is a dipole driver, invented by Oskar Heil, that uses a pleated polyester film diaphragm carrying printed conductors between magnets. As current flows, the pleats close and open like a bellows and squeeze air out sideways at about five times the speed of the diaphragm itself. A 25 mm (1 inch) wide strip moves about as much air as an 8 inch cone, with very low moving mass.

ARC Genesis is the third-generation Anthem Room Correction software, released in 2019, that measures a room with a calibrated USB microphone and computes minimum-phase digital filters for Anthem, Paradigm and MartinLogan products. It runs on Windows or macOS, corrects each speaker group from 20 Hz up to a user-set limit of 20,000 Hz, and recommends five microphone positions placed 2 feet (60 cm) from the first. The measurements feed filters that run inside the receiver or speaker.

Audyssey Dynamic EQ is a volume-dependent loudness compensation feature, launched at CEDIA 2007, that boosts bass and treble and lifts the surround channels as an AV receiver's volume drops below film reference level (0 dB). It is anchored to the 85 dB SPL cinema mix standard and offers 5, 10 and 15 dB reference level offsets for content mixed lower. On Denon models it also raises surround and rear channels by up to 8.5 dB at the default setting.

Audyssey Dynamic Volume is a real-time dynamic range compression feature that automatically adjusts audio levels to maintain consistent volume across different content sources and passages. It operates by analyzing upcoming audio signals and compressing high dynamic range content that follows low dynamic range material, with three intensity levels (Light, Medium, Heavy) that determine the maximum amount of compression applied.

Audyssey MultEQ XT32 is the top-tier version of Audyssey's automatic room correction system, used in AV receivers and processors to compensate for both time-domain and frequency-domain acoustic problems in a listening room based on microphone measurements taken during setup. It sits above the lower-tier MultEQ and MultEQ XT versions in filter resolution and is typically reserved for higher-end Denon and Marantz receivers, where it is often paired with companion Audyssey features like Dynamic EQ, Dynamic Volume, and LFC.

An AV receiver (AVR) combines processing, amplification, and connectivity in one chassis and powers speakers directly. An AV preamplifier/processor (AVP) handles decoding, switching, and control only—it requires external power amplifiers to drive speakers, enabling higher channel counts and independent amplifier scaling.

Bass management is the AVR or preamp function that routes low-frequency content from any channel to the loudspeakers actually capable of reproducing it — typically a subwoofer — based on each channel's Small/Large setting and a configured crossover frequency. It is distinct from the discrete LFE (.1) channel, which is a separately encoded effects track in the source program. The subwoofer output is the sum of the LFE channel and the bass redirected from any channel set to Small.

Bi-wiring runs two separate cables from one amplifier output to a speaker's HF and LF binding posts, with the speaker's internal passive crossover unchanged. Passive bi-amping uses two amplifier channels per speaker but still routes the full-range signal through that same internal passive crossover. Active bi-amping splits the signal with an electronic crossover ahead of the amplifiers and bypasses the speaker's passive crossover entirely.

Channel configuration notation (X.Y.Z) is the standard shorthand for describing a home theater speaker layout: X is the number of full-range, ear-level speakers, Y is the number of subwoofer/LFE channels, and Z is the number of overhead or height channels used for immersive formats like Dolby Atmos and DTS:X. A plain surround system without height channels, such as 5.1 or 7.1, is simply written as X.Y with no Z term.

CL2 and CL3 are the UL 13 / NEC Article 725 markings for power-limited cable that is allowed inside a wall: CL2 for Class 2 circuits with insulation rated up to 150 V, and CL3 for Class 3 circuits rated up to 300 V. CL3 may be used wherever CL2 is required, but not the reverse. Plenum spaces call for the P versions, CL2P or CL3P, and speaker wire follows the same rules because NEC Article 640 points to Article 725.

Class AB and Class D are the two amplifier topologies that dominate home audio. Class AB runs its output transistors in a continuously-conducting linear mode biased to overlap the push and pull devices, while Class D runs them as switches that are either fully on or fully off, with a passive LC filter reconstructing the audio waveform from a high-frequency pulse train.

A coaxial or concentric driver mounts a tweeter, or a tweeter and midrange, on the same axis as a larger bass or midrange cone so that both radiate from one point. A coincident-source design such as KEF's Uni-Q goes further and puts the tweeter at the acoustic center of the cone. Since the first Altec Duplex in 1943, the goal has been wider, more even off-axis sound and no crossover-region lobing. The cost is cone-to-dome interaction that designers manage with waveguides.

A compression driver is a loudspeaker unit whose dome diaphragm is much larger than the throat opening it feeds, so the sound passes through a phase plug into a horn at high pressure. Matched to a horn it can reach roughly 20% efficiency, about 10 times a cone or dome in free air, with bare driver sensitivity near 105 to 112 dB at 1 W and 1 m. Bell Labs published the design in 1928, and it is the basis of cinema and pro-audio high-frequency units.

Continuous (RMS) power is the sustained wattage an amplifier can produce indefinitely at a standard 8-ohm load without distortion or thermal shutdown; dynamic (peak) power is the maximum instantaneous output during audio transients, typically lasting tens of milliseconds and mathematically higher than continuous output. The distinction exists because power supplies can deliver burst current for brief moments but must dissipate heat continuously over time.

A waveguide is a shaped acoustic interface placed in front of a high-frequency driver (typically a tweeter) whose explicit purpose is to control the angular distribution, or dispersion, of radiated sound over a defined frequency range. By shaping the emitted wavefront, it lets a driver's off-axis output track its on-axis output at reduced level, rather than diverging into an uncontrolled tonal balance off-axis.

The crossover frequency is the point where an AV receiver's bass management hands low bass from a speaker set to Small over to the subwoofer. Denon receivers offer 40 to 250 Hz with an 80 Hz default, which matches the THX 80 Hz figure. The usual rule is to set it above the speaker's in-room -3 dB point, and owners report Audyssey calibration choosing values from 90 to 150 Hz after finding that point per speaker.

Crossover slope is the steepness of a filter's rolloff outside its passband, expressed in decibels per octave. The Linkwitz-Riley 4th-order alignment (LR4, 24 dB/oct) is the de facto standard topology in modern audio crossovers and the alignment used by THX-style bass management on the subwoofer feed. Each additional filter order adds another 6 dB/octave of rolloff.

Damping factor is the ratio of the nominal loudspeaker load impedance (typically 8 Ω) to the amplifier's source (output) impedance — a dimensionless number. It quantifies how strongly the amplifier short-circuits the speaker terminals and, by extension, how much the amplifier resists the back-EMF a moving voice coil generates at driver resonance.

Dialogue enhancement is any processing that raises speech relative to music and effects. It comes in two kinds: metadata-driven systems such as Dolby AC-4 Dialog Enhancement and DTS:X Dialog Control, where the encoder labels the dialogue and the decoder boosts it, and blind processors such as Sony's VOICE mode and Voice Zoom 3 or Samsung's Active Voice Amplifier, which find and lift speech in a finished mix. Broadcast research puts a useful boost at 6 dB, with 12 dB as the practical ceiling.

Dipole and bipole surround speakers use different driver configurations to create the ambient sound field behind and to the sides of a listening area. Dipole speakers wire drivers out-of-phase (180 degrees) to produce a null zone on-axis and a figure-8 radiation pattern, while bipole speakers wire drivers in-phase to maintain coherent bass and provide a larger sweet spot. Modern audio formats have shifted from dipole designs toward direct-radiating monopole speakers.

Dirac Live Bass Control (DLBC) is a paid add-on to Dirac Live Room Correction that designs one set of phase filters, delays and gains for all subwoofers and speaker groups below a chosen crossover, so the bass is optimized as a single system. Dirac lists it at $299 and requires the Room Correction license. Its target curve is split into a bass range shared by every channel and a higher range unique to each speaker group, and it is the prerequisite for Dirac's ART add-on when subwoofers are present.

A Dolby Atmos Enabled speaker is a discrete speaker module placed on top of a front, surround, or surround-back speaker that fires sound upward at the ceiling instead of straight in-ceiling installation. Rather than being a true overhead channel, it uses ceiling reflection to bounce sound back down to the listener, simulating an overhead effect. Dolby and speaker manufacturers position it as a compromise for rooms where in-ceiling or in-wall height speakers aren't practical.

Driver cone material (paper, aluminum, Kevlar) is the primary acoustic component that controls how a speaker reproduces sound by managing stiffness, damping, and resonance behavior. The material's physical properties—density, rigidity, and internal damping—directly determine breakup frequency, distortion character, and overall tonal balance.

Xmax (maximum linear excursion) represents the maximum distance a speaker's voice coil can travel from its rest position while maintaining linear motor control and remaining within the magnetic gap. When a driver is pushed beyond Xmax, the voice coil begins to exit the gap, causing distortion but not immediate mechanical damage.

Front-height speakers are mounted high on the front wall above the left and right mains, while top-front speakers are in-ceiling or on-ceiling units placed ahead of the seats. Dolby's installation guide puts front heights at about 30 degrees horizontal on the wall, or about 45 degrees of elevation if they must go on the ceiling. Dolby prefers overhead speakers to front heights, and an AVR needs the right label to place Atmos objects correctly.

The FTC Amplifier Rule, 16 CFR Part 432, sets how home-entertainment amplifier power may be advertised in the United States. Since the 2024 amendments, effective August 12, 2024, a power claim must be measured at 8 ohms across 20 Hz to 20 kHz with no more than 1.0% THD+N and labeled "FTC Power Output Rating." Any other rating must say it "was not tested under the FTC standard." The rule dates to 1974, and CTA has asked the FTC to rescind the 2024 amendments.

Gain staging is setting the signal level at every stage of an audio chain, from source to preamp to power amplifier, so each stage runs well above its noise floor and below clipping. In a home theater it means matching the receiver's preamp output to an external amplifier's input sensitivity, the voltage that produces full rated power. A 100 W amplifier into 8 ohms needs 28.3 V RMS, so a 1.0 V sensitivity means 29 dB of voltage gain.

Ground loop hum is a steady mains-frequency tone, 60 Hz in North America and 50 Hz elsewhere, that appears in speakers when two pieces of equipment share a signal ground and also reach the electrical ground by different paths, so a small current flows through the signal shield. Its harmonics at 120 Hz and above are usually called buzz. The usual home-theater culprits are the cable TV coax, a subwoofer line, and equipment on different outlets, and the fix is isolation, never lifting the safety ground.

A horn-loaded speaker couples a driver diaphragm to air through an acoustic impedance transformer—a narrow throat expanding to a larger mouth—converting high-pressure/low-displacement motion into low-pressure/large-displacement sound radiation. This design achieves roughly 10 times more acoustic power output than direct-radiating cone speakers for equivalent amplifier input, making horn speakers standard in cinemas and professional sound reinforcement.

Speaker impedance is the AC opposition to current flow at a given frequency, measured in ohms; it is a curve across the audible band, not a single static number. The label printed on the box — "8 ohms," "4 ohms," "6 ohms" — is a nominal impedance, defined under IEC 60268-5 such that the rated value is no more than 1.25 times the impedance minimum inside the rated band. The single-number rating is shorthand for the whole curve.

An infrasonic filter is a high-pass filter that attenuates frequencies at or below the lower threshold of human hearing (around 20 Hz) to protect subwoofer drivers from over-excursion and remove inaudible ultra-low-frequency energy that consumes amplifier power without producing audible sound.

The LFE (Low-Frequency Effects) channel is the separate, band-limited ".1" track in 5.1, 7.1 and Atmos mixes, defined in ITU-R BS.775-4 as an optional channel for high-level bass effects. It is limited to 120 Hz (capable of 20 to 120 Hz), recorded 10 dB low and played back with +10 dB gain. It is not the same thing as the subwoofer output: bass management also sends low bass from every other channel to the sub.

MCACC, the Multi-Channel Acoustic Calibration System, is Pioneer's automatic room calibration for AV receivers. A microphone at the seat captures test tones from every speaker, and the receiver sets channel levels, crossovers, distances and equalization, with a Standing Wave filter for room modes. On current Pioneer Elite receivers a Full Auto MCACC run takes 3 to 12 minutes and can include up to 8 additional listening positions, and the Standing Wave filters sweep 63 to 250 Hz.

A speaker's minimum impedance dip is the lowest value its impedance curve reaches within the rated frequency range, and it sets the heaviest load an amplifier sees. IEC 60268-5, as Dynaudio quotes it, says the minimum must be no less than 80% of the rated impedance, so 6.4 ohms for an 8 ohm speaker. Measured examples fall well below that: Archimago found 3.6 ohms in a speaker labeled 8 ohm compatible.

Phantom center is the setup where no center speaker is connected, so the AV receiver folds the center channel into the front left and right speakers and the dialogue image forms between them. ITU-R BS.775-4 downmixes the center into each front channel at 0.7071 (-3 dB). It works for a listener sitting on the center axis and degrades off axis: AES research puts the lowest comb-filter notch near 2 kHz, inside the speech band.

Port tuning frequency (Fb) is the Helmholtz resonance of a bass reflex (vented) enclosure, set by the port's length and area and the box's internal volume. At Fb the port delivers most of the output and the woofer cone barely moves; below Fb the port and driver fall out of phase and the response drops at 24 dB per octave. In a movie subwoofer, Fb trades extension against port noise and transient control: Hsu's VTF-3 MK5 HP, for example, lists tunings of 18 Hz and 22 Hz.

A power conditioner sits between the wall outlet and AV gear and combines some mix of surge suppression, EMI/RFI line filtering, per-outlet isolation, and sometimes voltage regulation or an extreme-voltage shutoff; no standard says which. Furman's Elite-20 PF, for example, is specified for 188 V peak clamping at a 6,000 V / 3,000 A surge and over 80 dB of EMI attenuation from 100 kHz to 1 GHz. It measurably changes the mains side; at the audio output of well-designed gear, measurements usually show no change.

A pre-out is an analog line-level output on an AV receiver or AV processor that carries each channel after input selection, processing and volume control but before the built-in power amplifier, so an external power amp can drive the speakers. Rated levels run higher than the 0.316 V consumer line-level reference: the Marantz AV 10 lists 1.2 V on unbalanced RCA and 2.4 V on balanced XLR. Pre-outs are what let a receiver act as a preamplifier.

Reference level is the SMPTE/Dolby cinema calibration target where dialogue averages 85 dB SPL (C-weighted, slow) at the listening position, with each main channel capable of 105 dB SPL peaks and the LFE/subwoofer capable of 115 dB SPL peaks. The acoustic scale is anchored to the digital scale so that 0 dBFS — the highest sample value a digital container can represent — corresponds to a 105 dB SPL peak on a main channel after calibration. On AVRs that follow the Dolby/THX convention, '0.0 dB' Master Volume is the reference position; negative numbers indicate attenuation below it.

Ribbon and dome tweeters are the two primary high-frequency driver designs used in speakers. Ribbon tweeters employ a thin diaphragm suspended in a magnetic field and typically offer linear frequency response and wide horizontal dispersion; dome tweeters use a rigid or flexible dome structure and are more robust, widely available, and cost-effective, with trade-offs in dispersion uniformity at high frequencies.

Sealed and ported are the two dominant subwoofer enclosure designs: a sealed box uses trapped air as a spring and rolls off gradually below its cutoff, while a ported (bass reflex) box uses a tuned port to add output but rolls off more steeply below its tuning frequency. The choice trades cabinet size, low-frequency rolloff steepness, and output efficiency against each other rather than one design being universally better.

Sensitivity is the sound pressure level a loudspeaker produces at one meter for a defined electrical input. It is published in two conventions: a power reference of dB SPL at 1 watt / 1 meter, and a voltage reference of dB SPL at 2.83 V / 1 meter. The two numbers are identical for an 8-ohm load and diverge for any other impedance.

SINAD (Signal-to-Noise And Distortion) is a single-figure audio-quality metric that ratios the test-tone power against everything else in the band — noise plus all distortion components — and reports the result in decibels. The canonical measurement is a 1 kHz sine-wave stimulus, and Audio Science Review popularized SINAD as the headline benchmark for DACs and amplifiers in consumer audio.

Speaker distance is the per-channel setting that tells an AV receiver how far each speaker sits from the listening position, so it can delay the nearer speakers and make every wavefront arrive together. Sound travels about 343 m/s at 20 C, so each foot of extra distance costs about 0.89 ms. Denon receivers accept 0.0 to 60.0 ft, and auto-EQ systems such as Audyssey measure the values for you.

Speaker level calibration sets each channel's trim so that the same test signal measures the same SPL at the listening position. SMPTE ST 202 uses 85 dB SPL C-weighted, slow for cinema, while home AVR guides use 75 dB per speaker with an SPL meter. Denon receivers offer a -12 dB to +12 dB trim range per channel, and auto-EQ systems such as Audyssey set the trims from microphone measurements.

Spinorama is a standardized loudspeaker measurement protocol that captures 70 frequency response measurements taken at 10-degree intervals across both horizontal and vertical planes in an anechoic chamber. The resulting data is compiled into four frequency-response curves (on-axis, listening window, early reflections, and sound power) that predict in-room performance and listener preference rankings with approximately 86% statistical accuracy for full-range speakers.

Group delay measures how quickly the phase of an audio signal changes across frequencies—expressed mathematically as the negative derivative of phase with respect to frequency. In subwoofers, it quantifies the time smear added to bass transients; ported designs typically exhibit 2–3× higher group delay than sealed designs at the same frequency, affecting perceived tightness and transient precision.

An electrical adjustment on powered subwoofers that adds delay or reverses polarity across a 0–180° range to align the subwoofer's driver motion with the main speakers' output. Proper phase alignment produces reinforcing bass; misalignment causes cancellation and audible bass loss.

The Voltage Protection Rating (VPR) is the UL 1449 let-through voltage of a surge protective device, measured with a 6 kV / 3 kA combination-wave surge and rounded up to a fixed step starting at 330 V, where lower is better. Type 1, 2, and 3 describe where a device is installed (service entrance, panel, or plug-in at least 10 m of wire from the panel), not how strong it is. A joule figure is a manufacturer-stated energy number that UL 1449 does not set, so the VPR and the UL listing are the ratings worth comparing.

Surround speaker angles are measured from the center-front line at the listening position. ITU-R BS.775-4 puts side and rear speakers in a 100 to 120 degree sector, and Dolby's 7.1.4 guide shows side surrounds at 90 to 110 degrees and rear surrounds at 135 to 150 degrees. Height is less critical: ITU says so, and Dolby wants listener-level speakers near 3.9 ft (1.2 m), with rears no higher than 1.25 times the fronts.

THD+N is the ratio of all non-fundamental energy at a device's output — harmonic distortion products plus noise, hum, and interference — to the fundamental test signal, expressed as a percentage or in dB. The canonical stimulus is a sine wave (1 kHz under IEC 60268 for analog systems, 997 Hz under AES17 for digital systems) measured over a defined audio bandwidth, conventionally 20 Hz to 20 kHz.

THX certification is a quality assurance standard that verifies audio-video receivers can reproduce movie soundtracks at the exact volume and fidelity intended by filmmakers in professional studios. Certified receivers undergo extensive laboratory testing and are designated for specific room sizes (Compact, Select, Ultra, or Dominus), with their volume dial's "0" mark calibrated to THX Reference Level (85 dB for main channels, 95 dB for subwoofers).

Timbre matching is choosing loudspeakers with the same tonal character, usually from one manufacturer's family, so a sound panning across the front, surround and overhead channels keeps one tone instead of changing color at each speaker. Dolby's Atmos guidelines tell installers to pick overheads timbre matched as closely as possible to the listener-level speakers. No single spec measures timbre; matching means the same tweeter, cone material and crossover voicing.

TV-as-center-channel features let a soundbar and the TV's own speakers play together. Sony's Acoustic Center Sync wires the TV in as the center channel of the soundbar system through an S-CENTER jack, Samsung's Q-Symphony plays the soundbar and TV speakers simultaneously, and LG's WOW Orchestra does the same for compatible LG TVs and soundbars over eARC. Each is brand-locked and model-limited, and each still needs an HDMI connection for the audio.

YPAO R.S.C. is Yamaha's room-correction tier, short for Yamaha Parametric room Acoustic Optimizer with Reflected Sound Control, found on the RX-V4A, RX-V6A and AVENTAGE receivers. Yamaha says it listens for early reflections from nearby walls and furniture, which muddy bass and the lower voice range, and corrects each speaker separately; multipoint mode measures up to eight positions. Independent measurements show its impulse-response filters work mostly between 80 Hz and 500 Hz.

Bass traps are low-frequency acoustic absorbers used to control room modes and decay time in the bass region — typically below ~250 Hz, and often below ~100 Hz where standing-wave problems concentrate. The canonical taxonomy splits them into porous (resistive, broadband) absorbers and resonant absorbers, with the resonant family further subdivided into panel/membrane absorbers (moderately tuned) and Helmholtz resonators (sharply tuned to a single frequency).

Critical distance is the distance from a sound source at which the direct-sound level equals the reverberant-sound level in a room. Listeners closer than this are in the direct-dominated zone; listeners farther away are in the reverberant-dominated zone. It is a property of the source and the room together, not of the speaker alone.

First-reflection points are the geometric locations on the side walls, ceiling, and floor where the direct sound from a loudspeaker bounces once before arriving at the listening position. Each speaker has its own set of these points, and the standard way to find them is the mirror trick: any spot where you can see the tweeter reflected in a flat mirror held against a surface is a first-reflection point for that speaker.

The Harman Target Curve is a frequency response standard derived from listener preference research that incorporates a bass boost below 200 Hz, designed to predict preferred loudspeaker performance in typical rooms. In headphone applications, approximately 64% of listeners prefer audio equalized to the curve; the underlying principles trace to decades of loudspeaker acoustics research, though headphone and room-correction implementations should not be conflated as identical.

The elevation angle is the angle measured from the primary listening position up to a Dolby Atmos overhead (height) speaker. For front and rear height speakers in a 7.1.4 reference layout, Dolby specifies 45 degrees as the target, adjustable between 30 and 55 degrees if the room won't allow the ideal placement.

Maximum SPL is the loudest undistorted sound pressure level a speaker and amplifier can deliver at the listening seat, and dynamic headroom is the margin between your average listening level and that limit. Cinema reference level sets the target: 85 dBC average per channel, which leaves 20 dB of headroom for 105 dB peaks, and the LFE channel carries 10 dB more gain for 115 dB. SPL at the seat is speaker sensitivity plus 10 log10(watts), minus 6 dB per doubling of distance.

Multi-Sub Optimization (MSO) is the practice of positioning and filtering multiple subwoofers so their outputs destructively interfere with room modes, reducing seat-to-seat variation in bass response rather than relying on a single subwoofer optimized for only one listening position. It is quantified using metrics such as Mean Spatial Variance (MSV), Variance of Spatial Average (VSA), and Mean Output Level (MOL), and is implemented via placement rules plus computed delay, gain, and EQ filters (e.g., using the MSO software with Room EQ Wizard measurements).

Room gain is a phenomenon where low-frequency sound pressure in a sealed room extends to lower frequencies than anechoic speaker measurements suggest, creating apparent bass boost below the room's lowest acoustic mode. Below the wavelength threshold where the room's longest dimension is half a wavelength, the room acts as a pressure vessel rather than a propagating waveguide.

A room mode is a low-frequency resonance that builds up at a specific frequency inside an enclosed room because the wavelength fits an integer number of times between parallel boundary surfaces. Mode frequencies are determined by the room's three internal dimensions, and modes dominate audible bass quality below the Schroeder transition (roughly 200–300 Hz in domestic rooms).

RT60 is the time, in seconds, for a sound's energy to decay by 60 decibels after the source stops. It quantifies how reverberant a room is and is the primary single-number descriptor of room acoustics in the standards used for listening rooms (ITU-R BS.1116) and recording studios.

The Sabine equation, RT60 = 0.161 × V / A (V in m³, A in metric Sabines), predicts the reverberation time of a room from its volume and total absorption. It was derived empirically by Wallace Clement Sabine, a 30-year-old Harvard assistant professor of physics, on 29 October 1898 after three years diagnosing the unintelligible Fogg Art Museum lecture room. The result is the foundation of modern architectural acoustics.

SBIR is a frequency-response notch caused by sound reflecting off a nearby wall, floor, or ceiling and arriving out of phase with the direct sound at the listening position. The cancellation lands at the frequency whose quarter-wavelength equals the boundary distance, producing a measured dip of 6 to 15 dB.

The Schroeder frequency is the transition in a room between the low-frequency region, where separate standing-wave modes dominate, and the high-frequency region, where dense modal overlap makes the sound field statistically diffuse. It is calculated as 2000 × √(RT60 / V) Hz, with RT60 in seconds and room volume V in cubic meters. A 54 m³ living room with a 0.5 s RT60 lands near 192 Hz, which is why small-room bass problems reach well into the vocal range.

Speaker toe-in is the inward angling of front speakers toward the listening position. It alters the balance between direct sound and room reflections by increasing high-frequency energy in the direct path while reducing early reflections from side walls, with tradeoffs between stereo imaging precision and soundstage width depending on the angle and room characteristics.

A standing wave is the stationary pressure pattern formed when an incident wave and its reflection of the same frequency superpose at a boundary, producing fixed nodes (minima) and antinodes (maxima) instead of a wave that propagates. Inside a bounded space these patterns only exist at frequencies where an integer number of half-wavelengths fits between the reflecting boundaries. The set of those supported configurations inside a room is what acousticians call the room's modes.

The stereo listening triangle is formed when two speakers and a listener position create an equilateral triangle, with the distance between speakers equal to the distance from each speaker to the listening position. This geometry optimizes phantom center imaging and stereo localization by ensuring equal timing and level cues at the listening position.

A hands-and-knees listening technique to locate the subwoofer's optimal placement in a room. By placing the subwoofer at the primary listening seat and crawling around the room while listening to bass-heavy test material, listeners identify positions where bass sounds tightest, most articulate, and most even across frequencies — without requiring acoustic measurement tools.

4K streaming bandwidth is the sustained internet speed a service asks for to play its Ultra HD tier. Published figures are 15 Mbps for Netflix, 25 Mbps for Disney+ and for Apple's Apple TV app, and 15 Mbps for Prime Video on Fire TV (Amazon says some apps want 20). Those are headroom targets: community captures put average 4K stream bitrates between 12 and 26 Mbps, far below the 92 to 144 Mbit/s of a UHD Blu-ray.

A 4K streaming device is an external box or stick that connects to a TV via HDMI to decode and output 4K HDR content, distinct from built-in TV apps. Decoding happens in the source device before HDMI transmission. External devices typically receive more frequent software updates and often offer better performance and codec support than smart TV apps.

Passive HDMI cables are unamplifed copper connections limited to roughly 3 meters for full HDMI 2.1 bandwidth (48Gbps), while active cables contain built-in electronics to boost signals for reliable transmission up to 25 feet (copper) or 300+ feet (fiber optic). The trade-off is cost, directionality, and power draw versus distance capability.

AirPlay 2 is Apple's network streaming protocol that sends audio, video, and screen mirroring from an iPhone, iPad, Mac, or Apple TV to a receiver over Wi-Fi or Ethernet, with synchronized multiroom playback across speakers. Samsung, LG, Sony, and Vizio build it into TVs, and brands such as Sonos, Denon, Marantz, and Yamaha build it into speakers and receivers. Its audio path tops out at 16-bit/44.1 kHz per Cambridge Audio, and Dolby Atmos over AirPlay needs iOS 18 or later.

Auto Low Latency Mode (ALLM) is an HDMI feature that lets a source device — a console, PC, or streamer — automatically signal a display to switch into its lowest-latency picture mode for gaming, then revert when the source no longer requests it. Introduced in HDMI 2.1, it removes the manual menu trip into Game Mode that traditionally had to be done before each play session. ALLM is optional in the spec and backward-compatible with HDMI 2.0 ports.

Apple TV 4K is Apple's tvOS streaming box. The 4th generation, announced October 13, 2026 for $299 and in stores November 13, uses an A19 chip with a dedicated AV1 decoder and one HDMI 2.1 output that Apple rates up to 2160p at 60 fps, with Dolby Vision (Profiles 8.1 and 5), HDR10+, HDR10, HLG and Dolby Atmos. It replaces the 2022 3rd-generation model (A15 Bionic, $129 at launch).

ARC is an HDMI 1.4 feature, introduced in 2009, that lets a TV send audio back to a connected AVR or soundbar over the same HDMI cable that carries video into the TV. Its audio link is capped at roughly 1 Mbps, which is enough headroom for stereo PCM and the lossy 5.1 codecs (Dolby Digital, DTS, Dolby Digital Plus) but not for lossless TrueHD or DTS-HD Master Audio. It has been superseded by eARC for lossless audio and lossless Dolby Atmos passthrough.

Auracast is the Bluetooth SIG's name for broadcast audio on Bluetooth LE Audio: one transmitter, such as a TV, sends LC3-coded audio streams that an unlimited number of nearby receivers can join, with an optional Broadcast_Code to keep a stream private. Unlike classic A2DP pairing, which links one source to one sink, a listener just picks the broadcast. Samsung TVs have supported it since 2023 and LG's 2025 OLED TVs followed, but it only helps if your headphones or hearing aids support LE Audio too.

Balanced XLR and unbalanced RCA are two audio signal connection standards that differ fundamentally in noise rejection and cable length tolerance. XLR uses three conductors to transmit opposing-phase audio signals, allowing differential amplifiers to reject common-mode noise, while RCA uses two conductors with no noise-rejection mechanism, making it vulnerable to electromagnetic interference and ground-loop hum over long cable runs.

Bluetooth audio codecs are compression algorithms that encode audio into smaller data packets for wireless transmission to headphones or speakers. The mandatory baseline is SBC (Sub-Band Coding); advanced codecs like aptX, LDAC, and LC3 offer higher quality or lower latency at different bitrates.

Cloud gaming latency is the total time delay between a player's input (controller button press) and the visual response on screen, composed of network transit, server processing, video encoding and decoding, and client-side rendering. Modern services deliver between 80–140 milliseconds end-to-end; under 40 milliseconds is an ideal target rarely met by current services, and latency above roughly 50-60 milliseconds is where most players notice the impact, with competitive games requiring sub-50 milliseconds latency to avoid measurable impact on precision and reaction time.

Coaxial S/PDIF is the electrical version of the consumer digital audio interface standardized as IEC 60958 type II, carried on 75 ohm coaxial cable with an RCA (or BNC) connector at a nominal 0.5 to 0.6 V peak-to-peak. It carries the same data as optical TOSLINK: two-channel PCM up to 24-bit/192 kHz or compressed 5.1 such as Dolby Digital and DTS. It cannot carry TrueHD, DTS-HD Master Audio, or multichannel PCM, so for lossless surround it is replaced by HDMI.

Display Stream Compression (DSC) is a visually lossless compression standard developed by VESA that reduces video bandwidth requirements without perceptible image quality loss or latency. By achieving 3:1 compression ratios, DSC enables high-resolution displays—such as 4K at 120 Hz or 8K at 60 Hz with 10-bit color—to operate within the physical bandwidth limits of HDMI 2.1 and DisplayPort 1.4.

Dolby Atmos FlexConnect makes a compatible TV the central Atmos object renderer for a set of wirelessly-paired accessory speakers that can be placed anywhere in the room. Built-in TV microphones run an acoustic-mapping calibration that locates each speaker and adapts the object scene to whatever non-canonical layout it finds. The technology was unveiled by Dolby on 28 August 2023 ahead of IFA 2023 and shipped first on TCL's 2024 TV lineup.

eARC is an HDMI feature, introduced in the HDMI 2.1 specification, that returns lossless and uncompressed audio (Dolby TrueHD with Atmos, DTS-HD Master Audio, multichannel PCM up to 8 channels at 24-bit/192 kHz) from a TV to an AVR or soundbar over a single HDMI cable. It replaces the bandwidth-limited legacy ARC (Audio Return Channel) and resolves the long-standing issue of streaming-app and built-in-tuner audio being downgraded before it reaches a connected sound system.

ARC (Audio Return Channel, HDMI 1.4) and eARC (Enhanced Audio Return Channel, HDMI 2.1) both send audio from a TV back to a soundbar or receiver over one HDMI cable. ARC is an S/PDIF-style link of about 3 Mbps, enough for compressed Dolby Digital, DTS and Atmos carried in Dolby Digital Plus. eARC raises the ceiling to 37 Mbps, with 192 kHz, 24-bit audio, 32-channel uncompressed PCM, Dolby TrueHD and DTS-HD Master Audio.

An Active Optical HDMI (AOC) cable that uses fiber-optic strands to transmit high-speed video and audio signals over long distances, combined with embedded copper wires for low-speed signaling and power. AOC cables enable full HDMI 2.1 bandwidth (48 Gbps) over runs up to 100 meters where passive copper becomes unreliable.

Fixed Rate Link (FRL) is the HDMI 2.1 signaling scheme that replaces TMDS for high-bandwidth video. It turns the old clock lane into a fourth data lane, runs 3 or 4 lanes at fixed rates of 3 to 12 Gbps each (48 Gbps total at the top tier), codes data as 16b/18b with Reed-Solomon error correction, and sets its rate by link training. HDMI.org says FRL is the only way to reach 4K at 120 Hz, yet a port labeled HDMI 2.1 may not include it.

HDCP 2.3 is the current revision of High-bandwidth Digital Content Protection, the link-layer encryption applied across HDMI, DisplayPort, MHL, USB-C, and several wireless interfaces to keep digital audio and video from being copied between source and display. Published by Digital Content Protection LLC on February 28, 2018, it is an incremental security-hardening of HDCP 2.2 rather than a new architecture, and the two revisions interoperate in both directions.

An HDCP handshake failure occurs when a source device and display cannot authenticate each other during the HDCP protocol's initial security negotiation, resulting in a blank or black screen rather than video playback. This fails safely—if authentication cannot complete, the system terminates the connection to prevent unencrypted content transmission. Version incompatibility, damaged cables, and incorrect power sequencing are the most common causes.

HDMI 2.1 is the version of the HDMI specification released by the HDMI Forum on November 28, 2017, raising maximum link bandwidth to 48 Gbps via a new packet-based signaling scheme called Fixed Rate Link (FRL). It introduces support for 4K at 120 Hz, 8K at 60 Hz, resolutions up to 10K, and a set of optional gaming and audio features including VRR, ALLM, QFT, and eARC.

HDMI 2.1 is a feature specification, not a single fixed bandwidth: the HDMI Forum's maximum is 48 Gbps, but ports labeled "HDMI 2.1" can legally ship at a lower tier such as 40 Gbps. All HDMI 2.1 capabilities -- including the higher bandwidth itself, VRR, and ALLM -- are optional, so the label alone does not guarantee a port's actual throughput.

HDMI 2.2 is the next major HDMI specification released by the HDMI Forum on June 25, 2025 (announced January 6, 2025). It doubles the maximum transmission capacity to 96 Gbit/s, up from HDMI 2.1's 48 Gbit/s, carried over the new Ultra96 HDMI Cable. The spec also adds the Latency Indication Protocol (LIP) for improved audio-video synchronization.

HDMI bandwidth is the maximum data rate a cable and port can transmit uncompressed video and audio. The three tiers—18 Gbps (HDMI 2.0), 40 Gbps (most HDMI 2.1 devices), and 48 Gbps (full HDMI 2.1 spec)—determine which resolutions, frame rates, and color depths are possible without compression.

HDMI has no maximum cable length in the specification; usable length is set by signal attenuation, which tightens as bandwidth rises. HDMI LA certifies every cable length separately and says Ultra High Speed (48 Gbps) cables longer than a few meters likely need powered, active electronics. Installers report passive 48 Gbps copper holding to about 3 m (10 ft), while active optical fiber cables reach 100 m or more.

HDMI-CEC (Consumer Electronics Control) is an HDMI feature that lets a single remote command and coordinate up to 15 CEC-enabled devices connected over HDMI. It has been part of the HDMI standard since the original HDMI 1.0 specification, released by the HDMI Founders on December 9, 2002.

HDMI-CEC (Consumer Electronics Control) is the single-wire HDMI feature, defined since HDMI 1.0, that lets up to 15 devices command each other from one remote. Every maker rebrands it: Samsung Anynet+, LG SimpLink, Sony BRAVIA Sync, Panasonic VIERA Link, Philips EasyLink, Sharp Aquos Link and Roku 1-Touch Play. All speak the same protocol on pin 13 at about 417 bit/s, so a TV menu entry ending in Link or Sync is almost always the CEC switch.

The Latency Indication Protocol (LIP) is an HDMI 2.2 feature, finalized June 25, 2025, that lets source devices work out latency adjustments so audio and video stay aligned across chains that include an AV receiver or soundbar. It targets setups where picture and sound take different paths, such as a soundbar on a TV's eARC port while a console feeds the TV directly. The ITU puts the audible threshold at roughly 45 ms of early sound or 125 ms of late sound, so the margin LIP has to protect is small.

Lip-sync error is a timing offset between sound and picture. ITU-R BT.1359-1 measured viewer thresholds of about +45 ms to -125 ms for detectability and +90 ms to -185 ms for acceptability, where a positive value means the sound arrives early. The ATSC's broadcast limit is tighter: audio no more than 15 ms early or 45 ms late at the encoder input. At home, the usual cause is sound arriving late after video processing or a wireless hop, and the usual fix is an audio-delay setting in the AVR, soundbar or TV.

Optical (TOSLINK), HDMI ARC, and HDMI eARC are the three ways a TV sends sound to a soundbar or receiver. Optical carries about 3.1 Mbit/s and tops out at stereo PCM or compressed Dolby Digital and DTS 5.1; ARC adds Dolby Digital Plus, which is what streaming Atmos rides on; eARC raises the link to 37 Mbit/s and is the only one of the three that passes lossless TrueHD, DTS-HD Master Audio, and uncompressed Atmos from a disc player through the TV.

Quick Media Switching (QMS, marketed as QMS-VRR) is an HDMI feature that uses the VRR mechanism to change the source's frame rate without the TV resyncing, which removes the 1 to 3 second blank screen that appears when a video starts at a different rate. It works only when resolution and dynamic range stay the same, and both source and display must support it. Apple TV 4K (2022 and later) and LG's 2023 and newer OLEDs were the first pairing.

Quick Frame Transport (QFT) is an HDMI 2.1 feature that reduces display latency by transmitting each video frame in a burst across the cable at higher rates, rather than spreading it across the full refresh interval. QFT shortens the vertical blanking period and is designed primarily for gaming and virtual reality applications where low latency is critical.

Speaker wire gauge is the American Wire Gauge (AWG) size of a speaker cable's conductors; a lower number means thicker copper and lower resistance. Per conductor, 12 AWG measures 1.588 milliohms per foot, 14 AWG 2.525 and 16 AWG 4.016. The standard design rule keeps round-trip wire resistance under 5% of the speaker's rated impedance, which allows 16 AWG up to 48 ft and 14 AWG up to 80 ft on 8 ohm speakers.

A subwoofer cable is a single coaxial RCA-terminated cable with a dense, low-resistance braid shield, built to keep mains hum out of the line-level signal between an AVR sub output and a powered subwoofer. It is electrically the same kind of connection as an RCA interconnect, and the 75 ohm figure is a carryover from video and digital coax that does nothing at bass frequencies. What separates a good sub cable from a generic one is shield resistance, in Blue Jeans Cable's hum test about 1.8 to 5.0 ohms per 1,000 ft.

TOSLINK is the fiber-optic connection that carries an S/PDIF (IEC 60958) digital audio signal as red light, roughly 3.1 Mbit/s for 48 kHz stereo PCM. It handles two-channel PCM and compressed 5.1 such as Dolby Digital and DTS, but it cannot carry Dolby TrueHD, DTS-HD Master Audio, or multichannel PCM. For a TV-to-soundbar link that means no lossless audio and no Dolby Atmos over optical, which is the gap HDMI ARC and eARC fill.

The Ultra High Speed HDMI Cable is the 48 Gbps cable class defined by the HDMI Forum in the HDMI 2.1 specification and launched in January 2020 as Category 3 in HDMI 2.1a. It is the only cable certified for every HDMI 2.1 feature, including uncompressed 8K at 60 Hz (with 4:2:0 chroma; 8-bit RGB at 8K60 needs about 49.7 Gbit/s, more than the link's payload, so it relies on DSC) and 4K at 120 Hz. Certification means testing at FRL signaling, low EMI and every individual cable length at an HDMI Forum test center, with a scannable label on each package.

The Ultra96 HDMI Cable is the cable certification tier the HDMI Forum introduced with the HDMI 2.2 specification on June 25, 2025, rated for up to 96 Gbps and all HDMI 2.2 features. It sits above the Ultra High Speed HDMI Cable, which is only applicable to links of up to 48 Gbps. Ultra96 is also a feature name for products running 64, 80, or 96 Gbps, so the badge on a device tells you which cable it needs, not how fast it runs.

DisplayPort Alt Mode is a USB-C feature that enables certain USB-C ports to send video signals to external monitors using the DisplayPort protocol through a single cable. It repurposes the connector's high-speed differential pairs to carry DisplayPort data while supporting simultaneous USB and power delivery, though not all USB-C ports support it and cable and device support vary widely.

HDMI Variable Refresh Rate (VRR) is a feature of the HDMI 2.1 specification that lets a gaming source — a console or PC — deliver each frame to the display the moment it is rendered, instead of on the display's fixed refresh interval. The HDMI Forum's stated benefit is that VRR reduces or eliminates lag, judder and frame tearing for more fluid gameplay. It is the cross-vendor analogue to NVIDIA G-SYNC and AMD FreeSync, sharing the VESA Adaptive-Sync lineage with G-SYNC Compatible.

AirPlay 2, Google Cast, Spotify Connect, and Tidal Connect are the four major Wi-Fi-based protocols for sending audio to networked endpoints — speakers, AVRs, and smart displays — over the local IP network. All four support multi-room scenarios and run over Wi-Fi, which makes them fundamentally distinct from Bluetooth's point-to-point radio link.

WiSA is a cross-vendor wireless multichannel speaker protocol for sending uncompressed surround audio from a source to certified speakers from any participating brand. The standard now spans three transports: WiSA HD (5 GHz dedicated radio, lossless), WiSA Discovery (entry-level 2.4 GHz), and WiSA E (embedded software running over standard Wi-Fi chipsets). Its defining feature is multi-brand interoperability — a transmitter from one vendor pairs with speakers from another.

65mm / 70mm film is the 5-perf large-format film system: a 65mm camera negative with a 52.15 x 23.07 mm capture area (Kodak) and a 70mm release print whose extra 5mm carries magnetic soundtracks. Descended from Todd-AO, it projects at 2.20:1 and offers about 2.6x the negative area of 4-perf 35mm. It is not IMAX 15/70, which is a separate 15-perf format; IMAX reported 52 film locations at the end of 2025, and no source gives a worldwide 5/70 total.

Apple Spatial Audio is Apple's headphone rendering feature: it takes 5.1, 7.1 and Dolby Atmos signals, applies directional filters so sound seems to come from around you, and on supported AirPods and Beats models can lock that sound field in place with dynamic head tracking. It is not a competing format to Dolby Atmos; Atmos is the content, and Spatial Audio is how Apple devices fold it down to two ears. On Apple TV 4K it needs tvOS 15.1 or later and a supported pair of headphones.

A bed is a channel-based track whose channels map to fixed speaker locations (up to 7.1.2 in Dolby Atmos). An audio object is a mono source carrying x, y, z position and size metadata that a renderer maps onto whatever speakers exist. A Dolby Atmos master holds up to 128 channels, a 7.1.2 bed plus 118 objects, which home delivery squeezes into 12 or 16 spatial-coding elements for streaming.

Auro-3D is a layer-based immersive audio format from Belgium's Auro Technologies that stacks a height layer, and optionally a top speaker, on a 5.1 or 7.1 surround layer. Its home layouts run from Auro 9.1 to Auro 13.1, with height speakers elevated about 30 degrees, and native content is packed into a standard PCM carrier by the Auro-Codec. Auro 9.1 uses the same speaker count as Atmos 5.1.4.

AV1 (AOMedia Video 1) is an open, royalty-free video codec from the Alliance for Open Media, finalized in 2018 as the successor to VP9. Netflix reports that AV1 now carries about 30% of its on-demand viewing and uses one-third less bandwidth than both H.264 (AVC) and HEVC, with 45% fewer buffering interruptions. A TV or streamer needs a hardware or software AV1 decoder to play it, and Netflix says 88% of large-screen devices certified from 2021 to 2025 have one.

PCM is an uncompressed audio format where the source device decodes audio before sending it to the receiver; bitstream bypasses source decoding and sends compressed audio directly to the receiver for decoding. Bitstream is required for object-based spatial formats like Dolby Atmos and DTS:X, while PCM simplifies receiver requirements but loses height-channel metadata.

Blu-ray region codes are a three-region playback lock (A, B and C) that the Blu-ray Disc Association requires players to enforce, while studios may leave any disc unflagged. A disc with no flags, or all three set, is called region free, and about 70% of major-studio Blu-rays are estimated to be. Ultra HD Blu-ray does not officially use region coding, but 1080p Blu-rays and DVDs still do on UHD players.

DD+ JOC is the lossy transport that streaming services use to deliver Dolby Atmos. It combines a conventional Dolby Digital Plus channel bed (5.1 or 7.1) with a Joint Object Coding side-data payload that lets the decoder reconstruct the Atmos object scene from that downmix. It is what you are almost always hearing when an app says 'Dolby Atmos' over the internet rather than off a disc.

Dialnorm is a metadata parameter embedded in Dolby Digital (AC-3), Dolby Digital Plus (E-AC-3), and AC-4 audio bitstreams that tells a decoder how loud the dialogue content is, enabling automatic playback attenuation for loudness consistency. The decoder attenuates the audio in the digital domain before D/A conversion to normalize dialogue loudness to a reference target, preventing volume jumps between programs and advertisements.

Disc bitrate and streaming bitrate both measure how much data carries each second of a picture, but the ceilings differ. The Ultra HD Blu-ray specification allows disc read rates up to 144 Mbit/s, with Blu-ray Disc Association video maximums of 108 Mbps on 66 GB discs and 128 Mbps on 100 GB discs, while Netflix recommends only a 15 Mbps connection for its 4K tier. More bits per second means less compression for the same title.

Dolby AC-4 is a lossy audio codec standardized by ETSI as TS 103 190 and selected for North America as the ATSC 3.0 broadcast audio system through ATSC A/342 Part 2. Dolby recommends 144 kbps for 5.1 where AC-3 needed 448 kbps, adds dialogue enhancement, and carries channels or Dolby Atmos objects. Its AC-4 IMS variant is how Tidal and Amazon Music deliver Atmos music to headphones and virtualized stereo speakers.

Dolby Atmos is an object-based immersive audio format from Dolby Laboratories that authors individual sounds as positioned audio objects in 3D space rather than as fixed channel feeds. The renderer in your AVR or soundbar then maps those objects onto whatever speaker layout you have, from headphones to a 24.1.10 home theater.

Dolby Atmos Height Virtualization is Dolby's processing that creates the sensation of overhead sound from listener-level speakers only, with no ceiling or upward-firing drivers. Per Dolby, it applies height-cue filters to the Atmos overhead audio, then mixes the result into 2 to 7 listener-level channels to suggest either 2 or 4 overhead speakers. It is a different method from Dolby Atmos enabled speakers, which bounce sound off the ceiling.

Dolby Atmos Music is music mixed as Dolby Atmos audio objects and streamed by services such as Apple Music, Tidal and Amazon Music. Speaker playback uses Dolby Digital Plus with Joint Object Coding (384 kbps minimum with 12 elements, 448 kbps with 16), while headphone and virtualized stereo playback can use AC-4 IMS. It is lossy: studios mix against a 13,824 kbps PCM render that listeners do not receive.

Dolby Cinema is Dolby's premium theater format, pairing Dolby Vision dual 4K laser projection with Dolby Atmos sound in purpose-built auditoriums. Christie's figures put the projection at up to 31 foot-lamberts (about 106 nits) in 2D, roughly twice a standard 14 fL screen. Dolby reported over 250 sites in 14 countries in 2020. It is a cinema brand; Dolby Vision on a home TV is a separate HDR format.

AC-3 is a lossy audio codec using Modified Discrete Cosine Transform (MDCT) compression with perceptual audio coding to remove inaudible information. Standardized as ATSC A/52, it became the mandatory surround codec for DVD-Video, ATSC digital television, and cable/satellite broadcasting, supporting up to 5.1 discrete channels plus a low-frequency effects subwoofer channel.

Dolby MAT (Metadata-enhanced Audio Transmission) is a transport wrapper, not a codec, that carries Dolby TrueHD or decoded Atmos audio over HDMI as PCM audio plus metadata. MAT 2.0 carries up to 31 objects plus LFE and metadata, works over HDMI 1.4 and higher and over eARC, and Dolby says every Atmos TV, soundbar and AV receiver shipping in 2021 included it, so you rarely choose it yourself.

Dolby Surround Upmixer is Dolby's latest surround sound expansion technology that converts stereo, 5.1, 7.1, and 9.1 channel content to support any speaker configuration, including overhead channels. It operates in the frequency domain to analyze and steer individual frequency bands into surround and height speakers. An evolution of Dolby Pro Logic IIz, it shipped with Dolby Atmos-enabled receivers starting in 2014 to render non-Atmos source material across modern speaker layouts.

Dolby TrueHD is a lossless, multi-channel audio codec built on the Meridian Lossless Packing (MLP) compression layer, used principally in Blu-ray Disc and UHD Blu-ray. On UHD Blu-ray it serves as the carrier for Dolby Atmos object metadata. No major streaming service delivers TrueHD — streaming Atmos uses lossy Dolby Digital Plus instead.

Dolby Vision is Dolby Laboratories' proprietary HDR format, introduced in 2014, that augments a base video stream with dynamic per-scene or per-frame metadata standardized as SMPTE ST 2094-10. It is mastered with up to 12-bit per-channel color and a 10,000-nit reference ceiling, and it is delivered through a small set of distribution profiles that differ in base codec, color space, and backward compatibility.

Dolby Vision 2 is Dolby's successor to Dolby Vision, announced 2 September 2025, that adds a new image engine, Content Intelligence (Precision Black, Light Sense, sports and gaming optimization, bi-directional tone mapping) and Authentic Motion, a creator-guided judder control. It ships in two tiers: Dolby Vision 2 for mainstream TVs and Dolby Vision 2 Max for premium sets. Hisense turned it on first, on 6 August 2026, and Dolby says Authentic Motion only works on newly authored titles.

Dolby Vision Profile 5 (dvhe.05) is a single-layer 10-bit HEVC stream in Dolby's proprietary IPTPQc2 color space with no HDR10 fallback, used for streaming. Profile 7 (dvhe.07) is the dual-layer Ultra HD Blu-ray profile: an HDR10-compatible base layer plus a minimal (MEL) or full (FEL) enhancement layer. Profile 7 falls back to HDR10 on non-Dolby displays; Profile 5 does not, which is why most Dolby Vision files shared on home servers are converted to Profile 8.1.

Dolby Vision Profile 8.1 is a single-layer 10-bit HEVC stream whose base layer is a standard HDR10 signal (cross-compatibility ID 1) with Dolby's dynamic RPU metadata alongside it. A Dolby Vision display applies the RPU; any other HDR display shows plain HDR10, so there is no washed-out fallback like Profile 5. Profile 8.1 is the common target when Profile 7 disc rips are converted for wide device support.

Downmixing folds a 5.1 or 7.1 mix into two channels. Lo/Ro (Left only/Right only) sums center and surrounds in phase at about -3 dB and survives a mono sum; Lt/Rt (Left total/Right total) puts the surrounds in opposite polarity so a Pro Logic decoder can recover them, but the surrounds cancel completely in mono. ATSC A/52 defines both, and the stream metadata can flag the preferred mode.

DTS Digital Surround (also called DTS Coherent Acoustics) is a lossy 5.1-channel surround-sound codec that serves as the backward-compatible core layer within DTS-HD Master Audio. On Blu-ray, the DTS core operates at 1.5 Mbps, enabling older AV receivers to decode the lossy stream while newer systems can access optional lossless extensions stored in the same bitstream.

DTS Neural:X is a DSP upmixer, not a codec, that extends stereo, 5.1 or 7.1 sources onto height and wide speakers in an AV receiver. DTS lists it at up to 5.1.4 channels, and testers found receivers that cap it at 7.1.4. In High-Def Digest measurements it ran 2 to 4 dB hotter in the height speakers than the Dolby Surround upmixer, and it pulls discrete effects upward while leaving ambience low.

DTS Virtual:X is a virtualization technology, not a soundtrack format. It processes any input from stereo up to 7.1.4 (11.1 channels) and uses psychoacoustic Virtual Height and Virtual Surround processing to suggest overhead and rear speakers that are not there. It is licensed to makers of soundbars, AV receivers and TVs, and it runs after decoding, so it works on Dolby, DTS and plain stereo content alike.

DTS-HD Master Audio is a hybrid lossless audio codec for Blu-ray that pairs a lossy DTS core substream (1.5 Mbps, backward-compatible) with a supplementary correction layer (up to 24.5 Mbps total), enabling bit-identical reconstruction of the original studio master. It supports up to 7.1 channels at 96 kHz/24-bit or stereo at 192 kHz/24-bit, with lossless quality equivalent to uncompressed PCM on the same source.

DTS:X is DTS's object-based immersive audio codec, designed to place sounds where they would occur naturally in space rather than locking them to fixed channels. On UHD Blu-ray it rides inside a lossless DTS-HD Master Audio bitstream; for streaming, a separate lossy DTS:X variant delivers the format at roughly 448 kbps. Unlike Dolby Atmos, the consumer codec is explicitly speaker-layout-agnostic, with the renderer mapping objects to whatever speakers the listener actually has.

DTS:X Pro is DTS's decoder and renderer package for home cinema that handles up to 30 connected speakers plus 2 subwoofers, a total of 32 output channels (written 30.2). It is the same DTS:X soundtrack format with more output capacity, built on the DTS:X decoder with the Neural:X spatial remapping engine and an object renderer. Before it, home DTS:X topped out at 11 main channels plus LFE, typically 7.1.4.

Dynamic range compression (DRC) narrows the gap between loud and quiet passages by lifting low levels, leaving mid levels alone and cutting peaks. In Dolby Digital it is metadata: ATSC A/52 defines dynrng gain words of plus or minus 24 dB and compr words of plus or minus 48 dB that a decoder may apply, scale or ignore. A receiver's night mode is the user switch that applies them, and it works only on the device that decodes the stream.

Eclipsa Audio is the brand name Google and Samsung use for 3D spatial audio built on IAMF (Immersive Audio Model and Formats), an open container specification from the Alliance for Open Media released under the AOM royalty-free license. IAMF carries channel-based layouts such as 5.1.2 and 7.1.4 or scene-based ambisonics inside a container that can hold Opus, AAC, FLAC or PCM audio. It is the royalty-free rival to Dolby Atmos, with YouTube uploads and Samsung hardware as its main footprint so far.

Filmed For IMAX is IMAX's filmmaker partnership program, launched in September 2020 as 'Filmed in IMAX' with six certified digital cameras. A title qualifies when it is shot on an IMAX-certified digital camera or an IMAX film camera and finished through IMAX's own post-production, so it can use the 1.90:1 or 1.43:1 expanded frame. The certified list reached ten cameras by March 2026, including ARRI, Sony, RED, Panavision and Fujifilm bodies.

HDR10 is an open high-dynamic-range video standard announced on 27 August 2015 by the Consumer Electronics Association (now CTA), built on the ITU BT.2100 family. It pairs 10-bit color, the BT.2020 wide color gamut, and the SMPTE ST 2084 Perceptual Quantizer transfer function with a single set of static metadata that travels with the title.

HDR10+ is a royalty-free, open dynamic-metadata HDR format announced on 20 April 2017 by Samsung Electronics and Amazon Video, then formalized as the HDR10+ Technologies, LLC joint venture by Samsung, 20th Century Fox, and Panasonic at IFA 2017. It is standardized as SMPTE ST 2094-40 and sits on top of the HDR10 base layer, adding per-scene or per-frame statistical metadata so a display can apply scene-by-scene tone mapping rather than HDR10's single static curve.

HDR10+ Adaptive is an extension of the HDR10+ dynamic-metadata format, announced by HDR10+ Technologies, LLC in January 2021, that uses a built-in ambient light sensor to adjust tone mapping to the brightness of the room in real time. It needs sensor hardware, so older HDR10+ sets cannot gain it by update. Its closest rival is Dolby Vision IQ, and its successor tier, HDR10+ Advanced, adds an HDR10+ Bright layer for higher peak brightness.

HDR10+ ADVANCED is an extension of the HDR10+ dynamic-metadata format, unveiled by HDR10+ Technologies LLC on 10 December 2025 and licensed from 2026. It adds six features: enhanced overall brightness, intelligent motion smoothing, local tone mapping, genre-based optimization, advanced color control and adaptive cloud gaming. By 2 September 2026 it was certified on nearly 500 devices and offered on thousands of Prime Video titles.

HDR10+ GAMING is a gaming HDR standard from HDR10+ Technologies LLC, unveiled at CES 2022, that combines variable refresh rate, automated HDR calibration between game and display, and source-side tone mapping for low latency. As of September 2026 the HDR10+ Technologies site counts 18 supported games, and the feature runs only on PCs with NVIDIA or Intel graphics connected over HDMI to a certified TV or monitor. Consoles are not supported yet.

HGiG (HDR Gaming Interest Group) is a volunteer cross-industry group that publishes best-practice guidelines for HDR gaming, organized by Microsoft Corporation and Sony Interactive Entertainment Inc. It is explicitly not a standards body — it does not write specifications, run compliance testing, license trademarks, or operate a certification program.

HLG (Hybrid Log-Gamma) is a broadcast-oriented HDR transfer function jointly developed by the BBC and NHK and standardized in ITU-R BT.2100 alongside PQ. It is scene-referred and carries no metadata, and the lower half of its signal range uses a conventional gamma curve so the same stream remains watchable on legacy SDR displays.

IMAX is a proprietary large-format cinema system that pairs a tall, steeply raked screen with its own projection and sound chain, sold in four projection tiers: 15/70mm film and dual-4K IMAX with Laser GT (both able to show the full 1.43:1 frame), then single-projector laser and older xenon digital (both 1.90:1). IMAX Corporation counted 1,876 systems in 91 countries at June 30, 2026, but only 52 of them were film-projection locations at the end of 2025.

IMAX 15/70 is the 15-perforation, 70mm film format: cameras expose 65mm negative horizontally, prints are made on 70mm stock, and the frame measures about 69.6 × 48.5 mm, nearly ten times the area of a 35mm frame. A print runs at 337 ft/min and weighs about 600 lb for just under three hours. IMAX listed 52 film locations at the end of 2025, and 41 venues could show The Odyssey on film.

IMAX Enhanced is a home-entertainment certification program run by IMAX and DTS that covers remastered titles, DTS:X sound and certified TVs, projectors, receivers and soundbars. Disney+ has offered IMAX's expanded 1.90:1 picture, up to 26% more image, since November 12, 2021, and added a DTS:X soundtrack option on May 15, 2024. Certified devices are recommended but not required to see the expanded frame.

IMAX's expanded aspect ratio is the taller picture frame IMAX uses instead of the 2.39:1 scope frame: 1.43:1 on 15/70mm film and dual-laser GT screens, and 1.90:1 on single-projector laser and digital screens. At equal screen width, 1.90:1 shows up to 26% more image than a conventional screen and 1.43:1 up to 67% more. On Disney+ the expanded scenes arrive as a 1.90:1 option under the IMAX Enhanced label.

IMAX with Laser replaces the xenon-lamp 2K projectors of IMAX Digital (introduced in 2008) with 4K laser-illuminated projectors, higher contrast, a wider color range and a 12-channel sound design. At the end of 2025 IMAX counted 757 laser systems against 1,089 xenon systems and no longer sells xenon for new signings. 'LieMAX' is forum slang, not a specification, for small 1.90:1 multiplex IMAX rooms.

Infinity Vision is The Walt Disney Company's certification for premium large format (PLF) movie theaters, announced at CinemaCon on April 16, 2026. It is a quality label, not a projector or sound format: an auditorium qualifies with a screen at least 45 feet wide, laser projection reaching 14 foot-lamberts in 2D or 6 in 3D, and 7.1 or immersive audio such as Dolby Atmos. More than 5,000 screens worldwide carried it by October 2026.

Low-Latency Dolby Vision (LLDV) is the player-led form of Dolby Vision, in which the source does the Dolby Vision tone mapping against the brightness the display reports in its EDID and sends a finished 12-bit YCbCr 4:2:2 PQ signal. Standard TV-led Dolby Vision instead hides a 12-bit picture and its metadata inside an 8-bit RGB container and lets the TV do the mapping. LLDV is what consoles use, and it is how Dolby Vision reaches HDR10 displays through an EDID-rewriting box.

LPCM is uncompressed multichannel digital audio in which amplitude is sampled at a fixed clock rate and quantized onto evenly spaced steps. Its bit-rate is simply sample rate multiplied by bit depth multiplied by channel count, which is what determines whether a given LPCM payload fits down an HDMI or eARC link.

MaxCLL (Maximum Content Light Level) is a static metadata value that specifies the nit value of the brightest single pixel used anywhere in HDR10 content. Displays use this value to inform tone mapping—compressing highlights to fit the display's peak brightness when mastering peaked higher than the TV can deliver. Unlike dynamic metadata formats such as HDR10+, MaxCLL applies uniformly to an entire content piece rather than adapting scene-by-scene.

MaxFALL (Maximum Frame-Average Light Level) is the HDR10 static metadata value, defined with MaxCLL in CTA-861.3, that records the highest frame-average brightness found anywhere in a title, in nits (cd/m2). It is stored once for the whole stream as a 16-bit number, is generally smaller than MaxCLL, and tells a display how bright the brightest whole frame gets, not the brightest single pixel. Published examples run from 22 to 500 nits.

PQ (Perceptual Quantizer) is the HDR transfer function published by SMPTE as ST 2084 in 2014, titled "High Dynamic Range Electro-Optical Transfer Function of Mastering Reference Displays." It replaces the gamma curve used in SDR and maps a normalized 0–1 signal to absolute luminance from 0 to 10,000 nits. PQ is the EOTF underneath HDR10, HDR10+, and Dolby Vision.

Premium Large Format (PLF) is the cinema industry's label for an auditorium sold at a higher ticket price than the standard screen, usually with a bigger screen, brighter projection, immersive sound and better seats. It is a price tier, not a standard: IMAX, Dolby Cinema, 4DX and ScreenX are licensed brands, while Cinemark XD, Regal RPX and AMC PRIME are exhibitor-owned. Comscore counted more than 950 North American theaters with PLF screens in 2024.

SMPTE ST 2094 is the family of standards defining dynamic metadata for color volume transforms (DMCVT), published from 2016 as six parts: ST 2094-1 (core), -2 (KLV encoding) and four application parts, -10 (Dolby), -20 (Philips), -30 (Technicolor) and -40 (Samsung). ST 2094-10 underlies Dolby Vision and ST 2094-40 is the basis of HDR10+. The four methods are not interchangeable, so a display must implement the one the content carries.

Sony 360 Reality Audio is an object-based music format built on MPEG-H 3D Audio that places vocals and instruments at positions in a sphere around the listener. 360 Spatial Sound Mapping is a different thing: Sony's speaker-virtualization and room-calibration processing in soundbars such as the BRAVIA Theater Bar 8 and Bar 9, which builds phantom speakers and plays Dolby Atmos and DTS:X. One is a content format for music; the other is a way a soundbar renders any content.

Static metadata (HDR10) is a single set of luminance and color values applied to an entire program, generating one tone-mapping curve for every scene. Dynamic metadata (Dolby Vision, HDR10+) instead carries per-scene or per-frame data, letting a display adjust its tone-mapping curve as brightness demands change throughout a title.

Visible defects created when video is compressed with lossy codecs that discard data to reduce file size and bitrate. Common artifacts include blocking (tiled appearance), banding (color bands in gradients), ringing halos around edges, and mosquito noise in smooth regions, all more prominent at low bitrates and in dark scenes.

HDR tone mapping is the process of adjusting HDR content's brightness values to fit a display's actual capability range without crushing detail. Streaming services increasingly use dynamic per-scene metadata to optimize this mapping moment-by-moment, while older HDR10 formats (on disc or stream) apply a single static curve to the entire piece of content.

UHD Blu-ray (Ultra HD Blu-ray) is a physical disc format that stores 4K video (3840x2160) encoded with HEVC/H.265 on 50GB, 66GB, or 100GB discs, with data rates up to 144 Mbit/s. It carries lossless audio formats like Dolby TrueHD and DTS-HD Master Audio that compressed streaming services do not offer.

Ultra Panavision 70 is an anamorphic 65mm film format that squeezes the image 1.25x horizontally in camera so a 2.2:1 frame projects at about 2.76:1 from a 70mm print. Used for Ben-Hur (1959), The Hateful Eight (2015) and Sinners (2025), it is the widest mainstream film ratio. On a 16:9 TV, 2.76:1 fills only 64.4% of the screen height, leaving bars that total 35.6%, and Panavision's current lens sets squeeze 1.3x rather than the original 1.25x.

VistaVision is Paramount's 1954 widescreen process that runs 35mm film sideways through the camera, exposing eight perforations per frame (37.72 x 24.92 mm by Kodak's figure) instead of four. The negative has about twice the area of a standard 4-perf 35mm frame, which is why directors revived it for The Brutalist and One Battle After Another. Most prints were reduced to 4-perf, and only four venues could project One Battle After Another in 8-perf.