AES Section Meeting Reports

Sacramento Valley - July 22, 2009

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On 7/22/09, John Dahl of THX came to speak to us about various aspects of THX including its qualification standards.
The first thing he talked about was the making of "The Deep Note" (the THX cresendo that you hear at the beginning of a THX movie). The THX "Deep Note" consists of 30 voices over seven measures, starting in a narrow range, 200 to 400 Hz, and slowly diverting to preselected pitches encompassing three octaves. The 30 voices begin at pitches between 200 Hz and 400 Hz and arrive at pre-selected pitches spanning three octaves by the fourth measure. The highest pitch is slightly detuned while there are double the number of voices of the lowest two pitches.
John then went on to talk about THX's standard of quality including acoustic requirements, technical requirements and architectural requirements required for THX certified movie theatres. THX is not a recording technology, but a quality assurance system that guarentees that THX certified theatres 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.
John then talked breifly about how THX got its name. It has been speculated that THX stands for Tomlinson Holman's eXperiment, which is a spin off of Lucasfilm. Tomlinson Holman of Lucasfilm developed THX 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.
John then breifly talked about the applications of THX in such things as home theatre receivers, car audio, THX certified recording studios, etc.

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AES - Audio Engineering Society