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THX Select and THX Ultra2 Certification General Questions

by August 30, 2004
Q: Please provide a brief historical perspective of THX.

A: In the early 1980s, many commercial cinema auditoriums in the U.S. suffered from poor acoustics and had inadequate audio systems. Cinema loudspeakers hadn't seen improvements since World War II, audience viewing angles were poor, and outside noise interfered with the on-screen presentation. As new technology was revolutionizing the art of filmmaking, the cinema environment was being left behind.

George Lucas felt that he and his fellow filmmakers were wasting their time perfecting sound in the professional mixing room, when the audience would never experience their true vision the way it was intended. Because the filmmaking and presentation processes are so highly technical and have so many variables, Lucas believed that the cinema industry could benefit from a quality control system to deliver a consistent level of performance, across all theatre venues.

Lucas hired Tomlinson Holman, an audio scientist and now USC film school professor, to study cinema sound and construct the technical building and Stag Theatre at Skywalker Ranch. Holman's work would eventually lead to the first THX specs for commercial cinemas and, much later, for home theatre components. The new company was named after Lucas' first film "THX 1138" and Tomlinson Holman's eXperiment. THX was launched in 1983 to coincide with the premiere of "Return of the Jedi."

Today, THX Ltd. provides products and services that provide consumers with an experience "as the director intended." We also provide exclusive technologies and quality control services for companies in all aspects of the creation and presentation of entertainment content. Our customers are Hollywood studios, professional mixing facilities, video game developers, software duplication companies, theater owners, consumer electronics manufacturers, automobile manufacturers and home theater equipment manufacturers.

Q: What does it mean to be THX certified?

A: A mark of excellence in the entertainment industry, THX Certification promises consumers and media professionals that the certified venues they visit, and the certified products they purchase, have been evaluated and tested to meet the highest standards for picture and sound performance. THX is the only third-party company specializing in quality assurance programs and technologies for home theatre component manufacturing. The company's Home Theatre Certification programs provide consumer electronics manufacturers with independent analysis of home theatre products, as well as additional expertise for their design and engineering efforts. It ensures manufacturers' systems and components meet or exceed the industry's highest levels for performance-long before they make it into the hands of consumers.

To achieve THX Certification, home theatre products must meet or exceed our performance requirements under "normal" playback functions. For receivers and controllers, we also add patented post-processing features such as ReEQ, Timbre Matching, Adaptive Decorrelation, Adaptive Speaker Array and Boundary Gain Compensation. When a product switches video, we test it to guarantee that it does not degrade the signal. If a manufacturer claims that their product can switch HD, we test that, otherwise we test it for SD signals. THX Ltd. does not test for product longevity and we do not test "custom" or "DSP" modes such as Cathedral, Sports and room compensation.

Q: What exactly does THX qualify electronics for (IE. Electrical parameters, processing capabilities, functional, etc)?

A: All of our electronic specifications are what would be described as "good engineering practices." Taken one at time, none of our specs are too difficult to achieve by the manufacturer. However, the value to consumers is that we insure that all THX products interact properly with all other THX products. Because today's home theatre products are so extremely complex, THX always finds a way to help licensees make a better product and improve the consumer experience.

Q: Everyone is familiar with the buzz phrase "THX Certified" but we want to bring this mystery down to an easy-to-digest level. Can we talk about first, the different levels of THX certification, and then speak as specific as possible about what types of criteria are involved in achieving such certifications?

A: THX Select is a more affordable version of THX Certification. It is designed to play at reference levels in rooms of approximately 2,000 cubic feet,. THX Ultra2 is a 7.1-speaker extension of the original Ultra spec. Ultra2 is designed to work well with multi-channel music and movie presentations playing up to reference levels in rooms of 3,000 cubic feet or larger. Each certification requires components to produce high volume levels, to play at a low level of distortion, and to disperse sound in specific ways, as well as to have extremely low noise and behave in a stable and predictable way.

We have worked with most of our licensees for many years and on numerous products. When working on a product from a company accustomed to our requirements, we typically invest 40-60 hours in testing and correspondence before issuing certification. When working with a new licensee, we often invest 120-200+ hours per product before granting certification. What all this means is that the product performs and performs well. A $500 THX Certified receiver will have a very high level of performance, while a $4,500 THX Certified receiver will have even higher level of performance and will include whatever additional features the manufacturer chooses.

Q: Please fill in and/or update/expand the table below that compares all commercial levels of THX certification for receivers/processors, amplifiers, loudspeakers and audio/video cables.

A: My answers are only generalizations because THX licensees pay for these specifications, and company policy refrains me from providing more detailed information.



THX Select

THX Ultra2


Current Technology

Receivers / Processors

5.1 Format


7.1 Format



Cinema Modes

THX Cinema

THX Cinema

Music Modes

THX Music

Bass Management



Video Bandwidth

As Claimed

As Claimed

Receivers / Amplifiers

Amplifier Current Capability

Sufficient for Program

Sufficient for Program

Signal to Noise Ratio






Phase Margin


On-Axis Frequency Response

Off-Axis Frequency Response

Impulse Response

Power Response



Audio/Video Cables

Lumped Parameters


Characteristic Impedance (video)

Insertion Loss

RFI/EFI immunity

Shielding methods

We were disappointed THX wouldn't share more specifications on their requirements for the metrics tabulated above due to their proprietary nature. However they assured us these are critical specifications they consider when certifying products.

Q: Does THX have minimal standards for the following metrics in home theater processors/receivers?

  1. Signal to Noise Ratio (SNR) ***Yes
  2. Channel trim tracking error ***Yes
  3. Bass management filter performance and functionality. ***Yes

Editor's Note: Bass management is one area where many licensees have difficulty getting it right the first time. By "right" we mean consistent across all combinations and functions.

Q: Something that is often talked about by consumers is whether or not THX Certification really has any relevance to the performance of a product. We'd love to have you talk a bit about how you perceive THX certification to impact a device's ability to accurately reproduce the movie-going experience.

A: Every THX Certified component is guaranteed to add to a system's ability to accurately present movies the way they were mixed by the filmmaker on the dubbing stage. Any piece of certified gear works perfectly well when used with non-certified gear. An image I like is one of a set of audio video windows between the consumer and the director sitting in the dubbing stage experiencing his finished work. Our job is to ensure each window in the chain is completely transparent.

The consumer experiences the work exactly as it was created. Some would say that their system is "better." We would say that a system can't present the content better than how the artist intended. This isn't to say that the consumer will like it or that they would prefer more bass or brighter colors.

The advantage of THX is that you can always go back to the original. Having the original as a reference gives the changes consistent meaning. THX doesn't care if you want more bass, you paid for the system and should listen to it in whatever way suits you. We do believe, however, that you deserve a consistent point of reference from which to depart. And that's what we provide.

Another way to say this is, that if something seems wrong, it's probably not the THX Certified component. This is a key and often overlooked point because, with modern high quality gear used within its designed limits, the room itself, the equipment setup and the calibration have much more influence on the sound than the inherent character of the equipment. This is not to say that the gear doesn't matter at all, it does, but a mediocre room or system setup will invalidate judgments about the gear by masking those differences.


About the author:

Gene manages this organization, establishes relations with manufacturers and keeps Audioholics a well oiled machine. His goal is to educate about home theater and develop more standards in the industry to eliminate consumer confusion clouded by industry snake oil.

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