An introduction to the Lucasfilm THX sound system, and how it is used to enhance the presentation of movies both in theatres and in the home.
INTRODUCTION
MONO
STEREO
QUAD
DOLBY STEREO
DOLBY SURROUND
DOLBY PRO-LOGIC
DOLBY DIGITAL
DOLBY DIGITAL-EX
DTS
DTS-ES
MPEG-II
SONY SDDS
THX
TIMELINE

Sound Formats

 

THX Logo  
   

THX SOUND SYSTEM

The THX logo appears on a few high-end home cinema products and software packages and many would mistake THX as a sound format, which is incorrect. THX was developed by Lucasfilm (THX means Tomlinson Holman's eXperiment) to establish a standard of quality for home cinema equipment. He became aware that the sound reproduced in different theaters using different hardware produces quite different sounds. The theory was that if cinema equipment could be produced to meet a set of standards, the sound wouldn't vary so much in different venues and the original soundtrack would be heard as closely to the original mastering as possible, as long as all the hardware components were THX certified. Many people believe that THX is a rival format, in the same way that DTS rivals Dolby Digital. In reality, THX is used as a partner to both DTS and Dolby Digital - it ensures that the best possible sound is produced regardless of the actual sound format used.

 
   
For a home cinema product (A/V amplifier, speakers, decoders, etc.) to be awarded a THX certificate, the product manufacturer has to prove that the equipment meets strict guidelines. These could be anything from the type of materials used, or the type of power transformer used, to details such as how much internal interference is created between the transformer and the audio signal. The THX certificate is awarded to products that meet these requirements and can be considered a mark of a quality. You will also see VHS Video tapes, Laserdiscs and in the future DVD, with the THX badge on the cover and a note saying 'Digitally Mastered For Superior Sound And Picture Quality'. This means that the movie has been transferred from the original print to the new format using equipment and techniques based on the THX standard and ensures that the home format has sound and picture quality as close to the original as possible. In is not necessary to playback THX software on home THX equipment, although doing so would be an advantage.  
   
The THX specification is designed for room sizes over 3000 cubic feet. A new standard of THX certification has recently been announced for the home cinema market for room sizes of 2000 to 3000 cubic feet. The new standard is known as THX Select, while the original THX equipment have been re-badged as THX Ultra.