What is THX, and how does it relates to Surround Sound and Movie Pictures?

THX Home Cinema - An Overview

Not a standard by itself, THX Home Cinema aims at delivering cinema-quality picture and sound to the home. At the same time…

Many do not have a true understanding of what the THX certification system and related technology is all about, nor what the different labels found on home theater THX certified gear really mean, yet to the 'everyday consumer', the 'THX' label signifies that the highest standards have been used.

and Home Entertainment

THX. Ltd was established in 1983 by George Lucas company. It started out as a program to correct inadequacies in film playback, ensuring that surround sound in theaters meets the standards set by filmmakers.

It then expanded into the home theater arena through its THX Home Cinema with product certification that makes it possible to implement Dolby and other surround sound formats in a uniform manner in the home.

The THX Home Cinema program, like its cinematic counterpart, ensures that the home entertainment consumer, experience movies as the director intended.

In other words, THX Home Cinema is not some surround sound format, but a quality assurance program that works in conjunction with the different surround sound formats, to deliver superior-cinema experience via quality picture and sound presentation, in the home.

Expressed differently, the THX Home Cinema certification program has been designed such as to fit the different surround sound technologies in their totality, into high-end home theater systems.

This means that THX is all about the technically competent and correct reproduction of any video and audio content - one that closely replicates the monitoring environment in the studio.

THX Home Cinema is able to achieve this through a double front approach:

	It defines precise specifications for hardware, e.g. THX certified main front channel speakers have to meet very specific design goals in terms of their horizontal and vertical radiation patterns.
	It also makes use of proprietary technologies and processes that form an integral part of the whole system.

This means that THX Home Cinema product certification programs and associated technologies are capable of delivering the ultimate home entertainment experience - thus providing superior playback of movies, music and games by ensuring accurate overall system response, intelligible dialog, pinpoint localization of sounds, and an accurate enveloping soundfield in which every seat is a good seat.

Further more, THX Home Cinema technology is designed to improve the interoperability of home entertainment products and applications. This does not mean that THX certified equipment works only with other THX equipment; rather any THX component can work with non-THX certified  gear, though in these circumstances, one may end up not enjoying the full benefits of THX-certified equipment all the way along the audio/video playback chain.

THX Home Cinema product certification covers speakers, AV receivers, DVD players, projection screens, room acoustic characteristics, and even interconnects. Lately, we have also started to see the first THX certified home theater projectors and DVR. Rigorous performance standards are used in the certification process to ensure the highest possible quality in home cinema and home entertainment. These standards cover all items in the audio/video chain and include also the source content material such as film-to-DVD and film-to-VHS transfers.

All THX Home Cinema certified products are labeled as 'THX' certified. In the case of DVD and VHS titles, the certification label may state 'THX Digitally Mastered for superior sound and picture quality', or simply THX DVD.

It is important to understand here that a THX DVD is not some proprietary format or content but a DVD that has been mastered to the industries highest standards under THX supervision.

In the case of system components, THX Home Cinema offers two main levels of certification - 'Select' and 'Ultra', which are further sub-divided according to the category of the different system components, while a third type of certification is also available for multimedia products.

Today, there are thousands of commercial cinemas, post-production studios, home entertainment products, DVDs and even games that have been designed according to THX rigorous standards and certified accordingly.

Major aspects of the THX Home Cinema certification program include:

• Re-equalization to compensate for the differing tonal balances that are appropriate in home theaters versus movie theaters, thus reducing the normally higher treble associated with the latter.

• Timber matching to complement the tonal qualities of the front and rear speakers to create a more uniform surround soundstage.

• Decorrelation of the surround channels in Dolby Pro Logic surround systems. The scope is to introduce minor diversity to the mono-surround channel serving the two rear speakers in this surround format, thus leading to a more diffused feel. This helps avoid the collapse of the centered rear soundfield produced by this monaural signal to the speaker closest to the listener. The latest THX Home Cinema certified receivers include adaptive decorrelation that automatically switches off the related circuitry when not required e.g. in Dolby Digital.

• Bass management based on a precise crossover cut-off point at exactly 80Hz, and a defined sub-woofer ‘sloop’ driver response. While THX recommends using a sub-woofer and setting all other speakers to 'small' to be able to place the subwoofer at the best sounding position in the room, at the same time, it also supports other options, including that of mixing the bass information from the left and right channels with the sub woofer channel.

• Amplifier Specs that are much tougher than on non-THX certified gear; these include the ability to drive low impedance (3.2Ohms) speakers while still producing a volume level of 105dB.

• A THX reference level (of 75dB) that aims at reproducing the same level, at which the movie was mixed in the studio.

• THX Optimizer or Optimode for DVD movie releases. This places a set of test patterns on the disc to enable the home theater enthusiast to tweak the video display to the same settings as used during the production stage.

THX Home Cinema Certification Levels

THX Home Cinema product certifications - 'Select', 'Ultra', and 'Certified Multimedia', and related sub-categories, are engineered to enable the certified component to perform best under specific room environments, usage conditions, and room size. Why?

Room size, room acoustics, and overall system design are all critical factors that will eventually determine your viewing and listening experience when watching movies, playing games, and listening to music in the home.

This means that the different THX certified product logos can help you choose the products that work best for your needs.

THX Select and THX Select2 Certified Products

THX Home Cinema certified products within the Select/Select2 categories are designed to deliver optimal quality audio and video presentations in small to medium sized home theater rooms.

More specifically, these are designed for a viewing distance of approximately 10 feet / 3 meters from the display to the listening position, and an overall room volume of circa 2,000 cu. ft.

THX Select2 specifically addresses receivers, incorporating new features and improved noise floor performance. Based on the same values and principles of THX Ultra2, THX Select2 Certified Receivers deliver higher quality to smaller home theater environments.

THX Select addresses the performance of speakers and DVD players. THX Select Certified Products complement the presentation of the THX Select2 category.

THX Ultra and THX Ultra2 Certified Products

The THX Home Cinema 'Ultra' and 'Ultra2' certifications are designed to ensure that certified products within these categories deliver top quality audio and video presentations in large home theater rooms.

More specifically, these are geared for a viewing distance of approximately 13 feet / 4 meters from the display to the listening position, and an overall room volume of around 3,000 cu. ft. room.

THX Ultra2 is considered as the benchmark for home theater products in that it offers uncompromised playback of multi-channel movies, music and games. The Ultra2 incorporates new features such as EX auto-detection and switching, high-bandwidth video switching, adaptive side-surround decorrelation, and boundary gain compensation. In addition, it also includes more power requirements for premium home theater receivers, pre-amplifiers, power amplifiers and speakers, to ensure the optimal distribution of a wide enough soundstage across the whole viewing area in the larger dedicated home theater room.

THX Ultra brings high-end performance to interconnects, equalizers, projection screens and DVD players, thus complementing the THX Ultra2 category. Unlike THX Ultra2 Certified Products, which are dependent on the room size, THX Ultra Certified Products are not.

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Theoretically, THX Home Cinema certified products within the THX Select/ Select2 and THX Ultra/ Ultra2 certification categories should deliver about the same level of immersive performance as long as your home theater environment falls within the specified room volume and viewing distance requirements as detailed by these different THX product certifications.

This means that if your home theater room is 2,000 cubic feet or less, THX Home Cinema Select2 certified receivers and THX Select certified loudspeakers should deliver about the same quality standards as the higher-end THX Ultra and Ultra2 components deliver in the larger environment.

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THX Certified Multimedia

The THX certification for multimedia products aims at delivering cinema-quality picture and sound to the desktop by ensuring that multimedia products comply with the THX rigorous standards.

While computer speakers and systems have the potential to deliver high quality pictures and sound, compatibility problems, non-standard set-ups and even complicated user controls may limit a potentially 'great' immersive experience.

For this purpose, THX have created performance standards specific to the challenges associated with Multimedia systems. The THX Multimedia certification program requires stringent specifications for the display, sound system, audio/video processing and even user controls. When you purchase computer systems or components carrying the THX logo, you are assured that special effects, graphics, and robust audio intended by film producers, musicians, and game developers, are accurately reproduced on your desktop.

In other words, the THX Certified Multimedia stamp is a guarantee that your computer setup is capable of delivering the highest possible fidelity for your MP3s, CDs, DVDs, games, and other digital audio sources, through cinema-quality audio and visual experience.

This also means that, as with other THX product certifications, THX Certified Multimedia is also associated with the viewing distance requisite; in this case, certified Multimedia products are designed for an optimum viewing distance of approximately 28 inches / 0.7 meters.

Interesting to note that in addition to product certification, THX has also come with THX Certified Home Theater Technicians.

Designing home theaters that are capable of duplicating the same audio and visual quality-performance as enjoyed in movie theaters and professional studios isn't always easy. For this purpose, THX Certified Home Theater Technicians are trained by THX to provide additional support on THX certified products and home theater room design.

THX Home Cinema Product-Certification Summary Guide

THX Home Cinema Logo	Certification Description	Product Types
	THX Ultra Certified Products are designed for top-performing products that are not dependent on room size.	Interconnects Equalizers Projection Screens DVD Players
	THX Ultra2 Certified Products are designed for large home theaters with a viewing distance of approximately 12 feet / 4 meters.	Speakers Receivers Pre-Amplifiers Power Amplifiers
	THX Select Certification relates to superior performance and complements the presentation of THX Select2 Certified Receivers.	Speakers DVD Players
	THX Select2 Certified Products are engineered and designed for the small to medium sized home theater with a viewing distance of approximately 10 feet / 3 meters.	Receivers
	THX Certified Multimedia Products are engineered for products with approximately a 28 inch / 0.7 meter viewing distance from display - namely the desktop.	Desktop Speaker Systems Soundcards

For more information on THX Home Cinema, please visit the THX website; there you will also find a complete list of THX Certified Products available from leading consumer electronics manufacturers.

More on THX Home Cinema and related technology will follow soon.	Last updated on: 18th Dec. 2006
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