Cambridge SoundWorks Speaker System manual Surround Reference, Dolby Digital, Dolby Pro Logic

Surround Reference

Dolby Digital

Dolby Digital (earlier called AC-3) delivers five discrete full-range channels (left front, center, right front, left surround and right surround) plus a separate Low Frequency Effects (LFE) channel. Many soundtracks on the latest generation laser discs, DVDs and High Definition Television (HDTV), are encoded with Dolby Digital technology.

When a 5.1 channel Dolby Digital program source is playing, such as from a Creative PC-DVD player, the Dolby Digital indicator light will illuminate automatically.

Note: Not every section of a DVD will be 5.1-channel encoded. On many DVD’s, only the main movie program will be available in 5.1 channel sound. Other supporting chapters (like a “Director’s Comment” section) may be in stereo or mono. These sections will not light the Dolby Digital indicator even though

the sound will be properly reproduced by the DeskTop Theater 5.1.

When listening to DVD movies with

5.1channel Dolby Digital sound, be sure to listen only to the digital program source and not a mix of the digital and analog signals that may be present. You can insure this by:

1)making sure all three CMSS indicator lights are off (MUSIC, MOVIE and STEREO/FOURPOINT).

2)muting the “CD” input of your computer’s software.

When playing a DVD game with a mix of Dolby Digital 5.1 sound (a digital signal at the SPDIF input) and sound card wavetable output (a signal at the analog input), be sure to en- gage one of the three CMSS settings.

Dolby Pro Logic

Dolby Surround is an earlier surround sound standard which is decoded with a Pro Logic processor in the DeskTop Theater 5.1. The Pro Logic steering circuitry derives separate center and rear channels from encoded stereo program sources.

Pro Logic processing provides a convincing movie soundfield when the material is specifically encoded for Dolby Surround. Most older stereo movie soundtracks will only be encoded for Dolby Surround, even though the program source may be a DVD’s digital output. Most DVD’s containing Dolby Surround program material will cause both the Dolby Digital and Digital Pro Logic lights to illuminate. DeskTop Theater 5.1 will decode these Dolby Surround programs through the digital Pro Logic decoder automatically.

CD-ROMs and CD’s with Dolby Surround encoding will feature the Dolby Surround logo at the beginning of the program or on the packaging. Process these programs by making sure all CMSS indicator lights are off and selecting the Pro Logic Analog Input setting of the Surround Mode button.

Do not select a Pro Logic decoding mode if the program material is not encoded for Dolby Surround. Excessive center channel output will result, and most stereo effect will be lost. Use CMSS “Movie” or “Music” modes to upmix stereo programs to a realistic 5.1 channel sound field.

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