We Don’t All Listen The Same Way
Dear Gary, I have been a subscriber and enthusiastic supporter of Widescreen Review for several years but only now feel compelled to write. The reason I am writing is to express my frustrations concerning your position on some of the characteristics of Dolby Digital, DTS Digital Surround and matrix PCM surround sound, which I feel are misleading. I have a home theatre setup which I have upgraded over the years and now includes Dolby Digital and DTS Digital Surround capability from both DVD and LaserDisc via a Sony E9000ES AV preamp/processor. Although I consider my system excellent, I realize your evaluations utilize systems costing many thousands of dollars more than mine, and we don’t all listen the same way. However, consider the following. I was not aware of your comparative review of the Dolby Digital and DTS versions of the Dances With Wolves DVDs until I had occasion to peruse a copy of WSR at a local book store. I had already purchased the Dolby Digital version, and was not aware until then that a DTS version was also available. As the only DTS software I owned up to that time was the Jurassic Park DTS LaserDisc, I was anxious to see how a DTS DVD performed, and since this would now enable me to make my own comparisons, I purchased the DTS version also. At first I was blown away until I realized that it was about 6dB louder than the DD version. So I made the necessary adjustments and came to some conclusions: perceived differences were minor or non-existent; or to take a word from your own reviews, subtle (which you used four times). Therein lies my complaint: your enthusiastic support of, and position on the superiority of DTS is obvious, and yet your reviews are also sprinkled throughout with the word subtle when describing those differences. I find that somewhat inconsistent, if not ambiguous. Also, I do not feel that DTS DVDs warrant a premium price. Another issue I would like to raise is that of the apparent differences in ambience or surround information. The difference between Dolby Digital/DTS and matrix PCM decoding is that the former formats are discrete and the latter is not; i.e., in the discrete formats, sounds generated in the surrounds are those placed there by the sound designers; whereas in a matrix system any sounds placed there by the sound designer as well as any miscellaneous, out-of-phase signals will appear in the surrounds. As proof of this, any music CD, whether labeled Dolby Surround or not, when played back with ProLogic decoding, will exhibit notable “ambience” in the surrounds whenever there is activity in the front channels. Therefore, I find your comparisons concerning the above somewhat misleading. By the way, your oft stated resulting in improper playback can be ameliorated by using Pro Logic decoding which will result in the proper mono sound from only the center channel. Also, I can empathize with you about your desire for a “holosonic” soundfield representation but I really don’t think motion picture sound designers share your ideal. They place sounds in the soundfield to match the action on the screen, and sometimes don’t even do an adequate job of that. And yet, a great sound design can transcend the method used; e.g., the Dolby Digital DVD of Air Force One stands out in my mind as a particularly excellent example. Lastly, I have some questions for which you might provide insight: 1. On DVDs of older movies in Dolby Surround, why are they mastered in 2-channel (compressed) Dolby Digital instead of uncompressed stereo PCM, which is one of the mandatory standards? 2. Why can’t studios/distributors issue DVDs with both DTS and DD soundtracks so that stores do not have to stock dual inventory and consumers who are DTS supporters do not have to make an additional purchase after the DTS version becomes available?
Bill Goldman, Playa del Rey, California
Editor Gary Reber Comments:
My personal sonic requirements are very high and our principal reference systems at the magazine reflect the pursuit of purist-level audio performance from DVDs, LaserDiscs and CDs. “Subtle” is often the name of the game, if not the norm when it comes to achieving purist-level audio performance, and no two people will always agree on the significance of the “subtle” characteristics of sound performance delivered from a similar performance class of components. I personally prefer the resolution and subtle, though at times dramatic, low level ambience recreation and improved harmonics of DTS Digital Surround to that of Dolby Digital. There are numerous nuances that are revealed when one compares the two digital audio formats using capable high-end components. For a large segment of our readers, subtle perceptions in sonic performance will be important and will justify their pursuit of the “very best it can be.” For other readers, the subtle differences will not be significant and they will be just as thrilled listening to low bit rate Dolby Digital-encoded digital audio. Still others will insist on very high bit rate encoding using higher sample rate (higher frequencies) linear PCM (pulse code modulation) and Meridian Lossless Compression (MLP), or the Sony-Philips single-bit/high frequency sampled Direct Stream Digital (DSD) encoding technology used in the Super Audio Compact Disc format. These purist audiophiles will swear allegiance to those audio encoding technologies and argue that such will more faithfully reproduce subtle overtones and harmonics. I happen to agree. But whether one’s system can resolve such subtleties is the question. If not, there is obviously no point in paying more for performance you can not recreate, unless, of course, you plan to upgrade the performance of your components. You know, if people could not hear or appreciate sonic subtleties then there would be no high-end audio market and all of us could save a lot of money and be happy with the mass-produced mainstream Japanese-Asia-manufactured components. I agree with you that most people can’t tell the difference between the two data reduced compressed Dolby Digital and DTS Digital Surround formats, nor for that matter, between an uncompressed PCM signal and a lossy compressed one. In such cases, lossy compressed low bit rate Dolby Digital is perfectly adequate. Since Dolby Digital was introduced, Dolby Labs has claimed that their lossy encoding scheme is transparent to the original master recording quality. Thus, why should there be a case made for DVD-Audio using Dolby-licensed MLP if there is no point to the merits of high bit rate linear PCM sonic performance? While you did note “minor” differences heard when comparing Dolby Digital to DTS Digital Surround on the Dances With Wolves DVD (I presume in favor of DTS), you do not feel that studios or distributors should be charging more for the DTS versions. I completely agree and we have advocated our position to the parties who control pricing. I also agree with your unstated but clearly implied feeling that while DTS has been touted as sounding superior, you are disappointed that the differences are relatively small. And by way of extension, your respect for Dolby Digital has increased, a respect that I have always shared with our readers, though often taken out of context as a negative position by some readers and outside critics who complain about my enthusiastic support of, and position on the superiority of DTS. I have based my position on years of critical listening experiences in numerous comparative reviews of Dolby Digital and DTS Digital Surround soundtracks. This has not been an easy task, as there are numerous variables to achieving a fair comparative A/B, which is virtually impossible to implement without special setup considerations, among which are a processor that can defeat Dolby Digital dialnorm, short for a Dolby encoding feature called “dialogue normalization.” This feature is supposed to maintain approximately the same level for dialogue as a listener switches among multiple Dolby Digital program sources such as DVD, HDTV, DTV, LaserDisc and DBS. The control data in the Dolby Digital bitstream of each particular program dictates the volume at which all channels will be calibrated. As a result, all DTS Digital Surround program material, whose signal’s dynamic level is unaltered from the printmaster soundtrack, will always sound 4dB to 6dB louder than the Dolby Digital soundtrack version, and at times vary during particular segments. To properly compensate for level differences one needs a processor with defeatable dialnorm or an accurate and calibrated level-matching setup to control the volume of all six channels. An interested home listener cannot simply drop in a DTS DVD/LaserDisc, then a Dolby Digital DVD/LaserDisc (various combinations) and accurately experience the sonic impression difference attribitual to the two coding schemes. As to the issue of the apparent differences in ambience or surround information between Dolby Digital/DTS and matrix PCM decoding, Dolby Surround is a three channel matrix with out-of-phase information directed to the mono surround channel. The Dolby ProLogic decoder recovers the out-of-phase information as a mono surround signal and the in-phase information as a center channel signal. In our reviews we focus on the subjective emotional impact of the soundtrack to deliver a holosonic™ experience, meaning scene-specific three-dimensional sonic envelopment throughout the soundtrack presentation. Often times the matrix PCM version achieves such satisfaction better than the discrete version(s), which tend to have less surround envelopment impact except at full scale signal during intense sonic descriptive scenes. It’s not that the discrete sound design cannot achieve holosonic impact as well as the matrix derived version with added surround “leakage,” but not often enough is the surround dimension paid enough attention to produce a more satisfying sonic experience. Interestingly, some of the new DTS DVDs have about 3dB less surround level compared to the same soundtrack released on DTS LaserDisc. This so-called corrective measure on the part of DTS to deliver the soundtrack with the “Dolby-reduced -3dB” level has resulted in a less enveloping experience. The older DTS soundtracks sounded more similar to the matrix PCM version than do some of the new DTS versions with the reduced -3dB surrounds. As you point out, we often state that DVD, not LaserDisc, monaural soundtracks are not coded properly to engage the Dolby Pro Logic decoding on all processors, resulting in improper playback. But more alarming is the trend toward purposeful dual-mono, which results in what we term “big fat mono,” a distasteful distraction. As to the answer to Question 1, I don’t know. As a purist I would want to see the very best transparent coding used. The answer to Question 2 is they can if they want, especially since higher capacity DVD-9 single-side, dual layer discs are now becoming the standard issue. It’s politics as usual, not common or good business sense that puts the consumer’s consideration first.
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