THX is a trade name of a high-fidelity sound reproduction standard for movie theaters, screening rooms, home theaters, computer speakers, gaming consoles, and car audio systems. THX stands for Tomlinson Holman's eXperiment. THX was developed by Tomlinson Holman at George Lucas's company Lucasfilm in 1983 to ensure that the soundtrack for the third Star Wars film, Return of the Jedi, would be accurately reproduced in the best venues. The distinctive crescendo used in the THX trailers is known as the "Deep Note".
The THX system is a recording technology, and it does not specify a sound recording format: all sound formats, whether digital (Dolby Digital, SDDS) or analog (Dolby SR, Ultra-Stereo), can be "shown in THX." THX is mainly a quality assurance system. THX-certified theaters provide a high-quality, predictable playback environment to ensure that any film soundtrack mixed in THX will sound as near as possible to the intentions of the mixing engineer. THX also provides certified theaters with a special crossover circuit whose use is part of the standard. Certification of an auditorium entails specific acoustic and other technical requirements; architectural requirements include a floating floor, baffled and acoustically treated walls, no parallel walls (to reduce standing waves), a perforated screen (to allow center channel continuity), and NC30 rating for background noise.
THX sets strict standards for high quality sound and images.
According to Tomlinson Holman, the inventor of the THX system, the name of the technology was deliberately chosen because it contained both a reference to his name, and to Lucas's early film THX 1138. The original name was "Tom Holman's Crossover" (Crossover being sometimes referred to as Xover) or the "Tom Holman eXperiment."
THX Ltd., the company that licenses THX and the associated technology, is based in San Rafael, California, but has offices in Burbank and Hollywood.
THX launched a certification program for HD video products to ensure HD projectors, LCDs, plasmas and DVRs meet high standards for quality. The TiVo Series3 HD DVR and a number of projectors from Runco and Vidikron became the first THX Certified HD products.
The THX II Certified Car Audio System can be found in many Lincoln automobiles produced since 2003. The system was recently recognized among the Best Car Audio Systems of 2006 by the editors of CNET.
THX Ltd. started a licensing program for home screening rooms in 2005, which requires standards similar in concept, though not in detail, to its cinema certification program; before this happened, there was a very small number of (very expensive) home theatres which were actually constructed to THX Cinema standards, most notable of actor and comedian Eddie Murphy.
This same "Deep Note" sound effect is almost identical to the opening sound effect in the song "Countdown To Zero", by the progressive rock group Asia. It was released on their 1985 album Astra, and predates the "Deep Note" by approximately three years.
The THX broadway logo on a DVD has a lower-pitched deep note, while the VHS/Laserdisc logo had a higher-pitched deep-note that was similar to "Wings" (1983).
The first theater THX was used in was at the University of Southern California's Eileen Norris Cinema Theatre as a part of USC's acclaimed film school. The Norris Theatre's THX system is currently second-best in California to that of the Grauman's Chinese Theatre.
While distinct from the THX Certification, the 10.2 surround sound system has also been spearheaded by Holman. 10.2 includes a front-left, top-front-left, front-right, top-front-right, surround-left, top-surround-left, surround-right, top-surround-right, center, "god" (top-center, above the screen), and front and back subwoofers. A 10.2 surround system is currently installed at the Integrated Media Systems Center at USC.
Some trailers have references to, or are stylized to match, various films. Examples include:
In The Simpsons episode "Burns' Heir", the THX logo plays extremely loudly causing the ground to shake, people's teeth to shatter and one man's head to explode. Despite this, Grampa Simpson still demands that they turn the volume up. This scene was made into an actual THX trailer.
The Simpsons Movie DVD and Blu-ray Disc releases have an unauthorized parody of the THX "Tex" trailers as an easter egg, where Homer Simpson becomes annoyed by a "Tex" caricature and eventually smashes it. A disclaimer after the trailer explains that neither the trailer nor The Simpsons Movie itself involved THX's input. Because of this, an imitation of the "deep note" sound is used and the logo used in the parody reads "TH".
During the scene where the animals are in a house in the film Over the Hedge, one of the characters accidentally steps on a television remote control, turning the TV on to reveal the THX logo and the "Deep Note" crescendo.
In the Boondocks episode ...Or Die Trying, Grandpa mimics the THX deep note crescendo when reassuring Jazmin that the theater they are going to is a quality theater.
At the beginning of the video game The Curse of Monkey Island the THX logo is replaced with the letters CMI and instead of the "Deep Note" crescendo we can hear a "Monkeys Screaming" crescendo. At the end text appears on the screen reading: "The monkeys are listening".
Before each episode of the Swedish Science Fiction comedy series Kenny Starfighter there is a THX-like logo but with the letters NDE replacing the original and a caption reading "Near Deaf Experience".
In the beginning of the film Tenacious D in The Pick of Destiny, Kyle Gass emits a long fart that reproduces the THX sound, and the logo THC shows on screen. The tag line underneath has been changed from "The audience is listening" to "The audience is baking".
During a period of time a lot of the pirated DVD-rips contained a trailer with the THX crescendo but instead of the THX logo this DiVX logo would emerge and the tag line underneath would read "the audience is leeching".
In an episode of George Lopez, George is talking about his new home theater, when he imitates a sound similar to Deep Note and says, "The George is listening."