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When you walk into your home theatre retailer you'll see both the THX and the Dolby Surround Pro Logic logos on a broad range of equipment choices.

What do these two logos mean, and how do these two technologies work together?

It's important first to understand that Dolby and THX are not competitors. In the movie theatre, Dolby equipment is at the core of the "A" chain of a movie theatre's sound system, the equipment installed in the projection booth to read the soundtrack from the film, decode it, and process it. Lucasfilm's THX division develops technologies and sets standards primarily for the "B" or "playback" chain that is, basically, the theatre's amplification and loudspeaker system, and the acoustics of the auditorium.

The relationship between the two in a home theatre environment is much the same. Without going into the technical details available elsewhere on this Web site (see Principles of Pro Logic Decoding), the Dolby analog soundtrack information "comes along for the ride" as a movie is translated from the big screen onto laserdisc or VHS videotape. Home viewers equipped with the appropriate speakers and a Dolby Surround decoder (which may be a stand-alone component or a built-in feature on a television set or laserdisc player) can recover that information and enjoy playback through left, center, right and surround channels, just as in the movie theatre.

Home theatre equipment which has gained THX certification takes this a step further, by incorporating technologies and characteristics which allow the home theatre environment to accurately recreate the film mixing stage where the soundtrack was created, allowing you to hear that soundtrack as the filmmaker intended. A visit to the THX Web Site can tell you more about the certification process and goals of the Home THX program. But there is literally not a THX home theatre system which isn't built around Dolby Surround Pro Logic capability . . . just as by far the majority of THX movie theatres are Dolby installations.

Are non-THX home theatre systems possible?

Of course . . . and only you can determine what system will best suit your interests, space and budget. But any exploration of your home theatre options should include a look at both Dolby Surround Pro Logic and THX, since together the two can offer you a very exciting sound-with-picture experience. (You will also want to consider whether upgradability to Dolby Digital (Surround AC-3), the new digital sound technology based on the Dolby Digital movie sound format and now available for the home, is important to you.)

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