First Impressions Of DolbyÆ Surround Pro Logic II

By Perry Sun, Movie Sound Editor

2-Jan-01

In Issue 41, we presented a special interview with surround sound extraordinaire Jim Fosgate on his latest, and purportedly his greatest achievement for surround sound, which is being licensed by DolbyÆ Laboratories under the name Dolby Surround Pro Logic II. Widescreen Review is now pleased to provide you an exclusive, firsthand evaluation. Dolby and Jim Fosgate were particularly generous to provide us with a working prototype of this latest matrix decoder, in its digital form, and to allow WSR to be the first publication to give Pro Logic II an intimate test drive. Additionally, WSR and a selection of members of the media were recently invited to visit Dolby's headquarters in San Francisco to audition Pro Logic II (as well as the company's other consumer-relevant licensing technologies and applications).The major contribution of Pro Logic II is unprecedented channel separation and soundstage stability, through what is known as feedback logic. Essentially, servo loops have been incorporated around the traditional logic steering process for Pro LogicÆ. The end result is a substantial improvement in matrix decoding performance through feedback-controlled steering, which is dynamically adjusted according to conditions imposed by the input signals into the decoder.In addition to the improved performance with separation of channels, Pro Logic II offers left-right surround capability. Therefore, a greater sense of expansiveness and envelopment should be perceptible and similar to what can be experienced with discrete 5.1-channel digital sound.At the outset, what I discovered with Pro Logic II was the creation of a soundfield that was undeniably wide, articulate and perhaps most importantly, stable. In other words, I was immersed within a soundstage that had uncanny openness, while directional placement of sounds were definite, and there was little or no detectable collapsing of the spaciousness that sometimes occurs with Pro Logic processing.With music recordings that had quite a bit of atmosphere to them, such as those from Enya, Enigma or Jean Michel Jarre, the Pro Logic II decoder predictably rendered holosonic soundstages with immense depth. With material exhibiting both ambience and sonic directivity, Pro Logic II seemed to be able to deliver both effortlessly, and seemingly without compromise of one or the other.What about Pro Logic II's performance with movie soundtracks? One particular movie that was found to be useful for this evaluation was ""Star Trek: First Contact."" The opening scene, Captain Picard's ""nightmare"" of being assimilated into the Borg collective, offered a wonderful opportunity to test this new matrix decoder's ability to generate and maintain wide, cohesive imaging. And indeed, this is what I encountered with Pro Logic II. The soundfield was certainly impressive, with ample split surround activity that at times convincingly tracked on-screen events.When I listened to Pro Logic II for the second time at Dolby Laboratories, what I found reaffirmed my initial observations at our facility. In addition to the expansiveness and sonic placement, I also was able to detect, rather interestingly, some side-wall imaging. Perhaps most significantly, comparisons with existing surround sound schemes strongly indicated an improvement in performance for Pro Logic II.All in all, what I heard was certainly impressive, and I am absolutely convinced that Pro Logic II is truly something different, and to my ears, a substantial advancement over other matrix-based processing approaches. I""m certainly looking forward to the first products next year with Pro Logic II, and the earliest possible opportunity to again enjoy very fine matrix surround sound.(A complete report on our Dolby Pro Logic II impressions, as well as more detailed information will be available in Issue 45 - January/February 2001.)