Dolby Digital Surround EX With A ProLogic Receiver?
Dear Gary: If I were to run the left and right surround channels of a Dolby Digital receiver into the left and right analog audio inputs of a Dolby ProLogic receiver and hook up all five speakers from the ProLogic receiver, to where would the "EX center surround channel" be extracted? The center channel speaker of the ProLogic receiver, the surround channels of the ProLogic receiver, or a combination of both? If I only hook up the left, center, and right channel speakers from the ProLogic receiver and play it in Dolby ProLogic, will it extract the "EX center surround channel" only? What would be extracted for the surround channels if I were to hook them up? Is it actually better (and cheaper) to use a ProLogic-capable receiver for extracting the "EX center surround channel" instead of purchasing a separate processor and amplifiers? Both would work virtually the exact same way and sound really no different, right? Would there be time alignment problems when using a ProLogic-capable receiver to extract the center surround channel? If so, how can the time alignment issues be solved?
Jason Steg
Editor Gary Reber Comments:
Jason, to clear up your perspective of "Surround EX" pretend your back surround hemisphere is your front soundstage hemisphere. Now then, use a ProLogic-capable or Circle Surround-capable processor to "decode" the otherwise phantom "center" image just as the processor decodes and generates a hard center front soundstage channel from the in-phase and equal amplitude signals present in the two-channels processed by the matrix decoder. In short, use only the "center" output of the processor to derive the "Surround EX" signal. You may use a Dolby Surround or ProLogic receiver or processor, a Circle Surround processor, an adapter such as the ADA 6.1 or the SMART Circle Surround EX (CS EX, Jr.), or simply experiment with a "Hafler" surround circuit that requires no additional power amplifier to support the derived center back surround channel. Of course, you could always invest in the new Lexicon MC-1 with certified "THX Surround EX" built-in processing or next-generation receivers and surround processors with "Surround EX" processing to be introduced in early 2000. To ensure proper time positioning of the center back surround speaker(s) physically locate the speaker(s) on the equal time-distance arc, thus not in a straight line across the back with your left and right surround speakers.
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