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DVD Between the Lines

The Sound of DVD: 5.1 Mixing Opinions Part 1

Mark Waldrep

With the advent of the DVD format, it seems the record industry is once again getting excited about multichannel audio playback. Any DVD-based digital system can reproduce five full-frequency channels and a dedicated Low Frequency Enhancement (LFE) channel, which account for the ìfiveî and the ìpoint oneî extension in the familiar 5.1 naming convention. But enabling a single component of the hardware necessary for DVD-Audio is only one of the challenges to delivering on its promises. The next challenge: to educate and demonstrate to musicians, producers, and consumers the richness of a listening experience that has been conceived, realized, and delivered in 5.1-channel surround sound.

First, it is important to distinguish the ideal listening environment, speaker, and subwoofer arrangement for music, as opposed to the audio element of video-oriented titles. Consumers that already own a surround sound system are probably not adequately prepared to handle the requirements of multichannel music deliveryóand millions are already installedóbecause the parameters for making a motion picture sound good in multiple speakers are somewhat different from the needs of a dedicated music experience. Firstly, all of the speakers need to be identical (direct reflectors, not dipoles) and capable of full-frequency reproduction, due to the complexities of DVD-Audio machines and the lack of bass management in current A/V receivers. Speaker placement is also critical [see sidebar in ì24-Bit Beethoven,î this issue, pp. 30-36óEd.]. An ideal music system should locate the sweet spot in the middle of a circle, with the speakers arrayed around the perimeter.

Now that the speakers are correctly arranged, the real question of how to use the speakers comes into the equation. Should music mixers use the center speaker? For engineers mixing audio for movies, itís a no-brainer. The majority of the dialogue comes from the center and demands that a clear, well-focused middle image be established. In fact, thatís why the center speaker was added to the quadraphonic arrangement that was worked out in the 1980s. Music, on the other hand, successfully creates a phantom center by sending the same signal to both the left and right sidesóno need for a separate middle speaker.

At Surround 2001 and other music-related conferences, many recording engineers and producers have stated their unwillingness to employ the center speaker and have demonstrated compelling mixes in the left and right fronts and surrounds. According to producer/artist/engineer Alan Parsons, a complete surround image can be produced by using each pair of speakers as a sort of stereo setup capable of having its own phantom center. His argument is based on principles that have worked within the stereophonic world for decades. Besides, he adds, if the lead vocal is placed solely in the center speaker then, by simply turning off that channel, consumers have the perfect clone for the karaoke circuit. He played a mix from Al Stewartís Year of the Cat and invited the audience to drift around the space to gain a greater appreciation for the quality of the presentation. It worked very well.

Some in the audiophile pressóand certainly in the equipment manufacturersóhave presented another viewpoint: the more speakers, the better. The standard 5.1-channel surround setup has been installed in a surprising number of households (over 20 million at last count), and has convinced consumers that sound is a major part of the home-viewing experience. If the center speaker is used for all of their television and movie watching, then why not use it for music playback? Several new extensions to the 5.1 standard are being promoted by DTS and Dolby Labs, which would place an additional speaker in the rear-center position to ìsolidifyî the rear sound. High-end 6.1 receivers, with the ability to extract the added channel, have begun to appear in the market. And the more-is-more notion can be taken to extremes, as shown by Tomlinson Holman of TMH Labs, who demonstrated a 10.2 playback system at CES. He believes that a better sound environment can be realized with channels for height in addition to more speakers placed around the periphery. I heard a mix of a Herbie Hancock tune and was very impressed. It does beg the question about how many speakers would ultimately be enough. An automobile at the same show had 16 speakers strategically placed around the interior, but it was only playing a stereo CD!

AIX Media Group is working with electronic music pioneer Mort Subotnick on a DVD-Audio/Video project for Mode Records. Two seminal quadraphonic works, Touch and A Sky of Cloudless Sulfur, have been digitally remastered from the source tapes and prepared for the release in 5.1. Though the original composition was designed for four speakers, the new release will employ the center, though not in a substantial way because of an unfortunate experience that another label had with a four channel-only product. It seems that consumers thought something was wrong with their equipment because no sound came from the middle. My own mixes follow this compromise approach; I use the center channel, but allocate most of the sound to the left and right to reinforce a center image.

Of course, the only way to decide what you like is to hear releases that embrace these two points of view. There are many multichannel titles from DTS, and other DVD-Audio releases are becoming available. But, as more titles reach consumers, a more fundamental question remains: what musical decisions should be taken into consideration when mixing 5.1-channel surround sound? Stay tuned.


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