What is THX?

We've all, no doubt, seen equipment or places branded as THX certified, but what does having the three-letter logo actually mean?

Derek Fung
Derek loves nothing more than punching a remote location into a GPS, queuing up some music and heading out on a long drive, so it's a good thing he's in charge of CNET Australia's Car Tech channel.
Derek Fung
3 min read

We've all, no doubt, seen equipment or places branded as THX certified, but what does having the three-letter logo actually mean?

What's the difference between Dolby and THX?

THX-branded goods and services have successfully passed through particular sets of measurable and subjective tests set by the company.

Dolby, on the other hand, is a company that specialises in noise-reduction and audio-compression technologies. These, along with the appropriate Dolby logo, are then licensed to manufacturers for use in their products.

What does THX certify?

The company primarily deals with audio matters, applying its stamp of approval on home-theatre and audio equipment, as well as cinemas, theatres and car audio systems. Recently, though, the company has begun to certify televisions for visual quality.

What does THX certification mean?

In terms of audio equipment, a THX-certified amplifier, receiver or speakers, say, will reproduce sound at reference quality for a given room size. So, if the components are set up correctly, a THX-certified system will play back sound as it was heard in the mixing studio.

Keep in mind, though, that there are varying levels of certification. For example, systems that are designed to work in a living room of up to 57m3 are eligible for the Select 2 mark, while those that are meant to work in rooms of up to 85m3 can qualify for the Ultra 2 level.

Systems for smaller rooms may qualify for I/S Plus Systems certification. Controversially, the company has recently launched a Certified Multimedia Products level for PC speakers and equipment, the sound from which needn't fill an entire room, but just the area immediately around the computer.

If a cinema or theatre is to receive the THX seal of approval, it must meet certain design and engineering criteria. These include noise isolation from the outside world and reverberation control via noise-absorbing panelling. THX-certified cinemas also feature speakers placed in a baffle wall behind the screen to improve sound quality from the centre of the sound stage.

As far as televisions are concerned, the company tests for uniformity of colour, brightness and contrast across a panel, as well as anti-aliasing performance, colour temperature and other undisclosed measures.

What else does the company do?

THX also runs training programs for audio engineers, sound-system installers and the like, teaching them the basics, as well as the advanced techniques and theories involved in calibrating equipment and room layout.

From time to time, the company will also purchase randomly selected certified items from stores to ensure that the products that are on sale are exactly like those that passed through the certification process.

Who runs THX?

Since 2001, THX has been an independently run company. From standard's creation up until that point, it was a part of Lucasfilm, the George Lucas-run company behind the Star Wars films.

The initial THX specification was generated to ensure that certified cinemas would reproduce the audio track for the initial Star Wars exactly as George Lucas had intended it.

What does THX stand for?

The first two letters stand for Tomlinson Holman, the inventor of the initial standard, while X is for crossover. Neatly, THX also references the first film that Lucas directed, THX 1138.