Experimentation The possibilities opened by the immersive qualities of digital surround sound are exactly the type of tools that many composers, musicians and sonic artists are seeking to influence their production process and to expand the sounds and spaces that listeners can perceive.
For many years, composers and performers have attempted to create new and interesting environments in a live performance by surrounding an audience with performers or loudspeakers and creating unusual and unique acoustic spaces. Producer Steven Epstein knows of composers who are planning to use digital surround formats to realise spatially on disc what they're achieving in a live situation. Engineer Jake Nicely is working with musician Bela Fleck to produce an album that sounds 'as if you were standing in the centre of a blue-grass jam session and all the players are around you'. Producer Chris Steinmetz identifies exactly the different approach taken to digital surround sound by popular music compared to classical music, when he describes 'building the mix from the centre - being inside the soundfield, as opposed to the live situation where they have ambience in the back and are more conservative'.
All these different approaches are valid in the context of exploring new ideas and techniques available with 5.1 surround sound delivery. Classical music production may well represent one end of a spectrum of views on digital surround sound, where the surround format is used to create more clearly the feeling of being immersed in the acoustic environment in which the performance has taken place. Mixing engineer Mick Guzauski recently completed the surround remix for Michael Jackson's Thriller album, well known to many millions of listeners worldwide for hits including Billy Jean and the title track. This was Guzauski's first experience of mixing for 5.1 and when asked for his first impressions, he replied: I actually found it easier to do than a stereo mix because you don't have the clutter that can build up just from having to put all the elements into two channels. Also, you could make the individual sounds bigger; you don’t have to filter or EQ little portions of the range up or down to make it fit into a smaller soundfield.
Many listeners are purchasing the home theatre systems required for surround sound reproduction, are discovering that the new soundfield is exciting to listen to and are demanding more material be available. They may currently be prepared to pay a premium above normal stereo CD prices for the new format, but they are now more discerning about the quality of the technology. They can hear the envelopment of the three dimensional soundfield more clearly, and can hear every little nuance of every instrument. Producer Chris Steinmetz has a focus on where the technology is leading: But when the new generation gets in tune with this new format, they're so technically savvy they're not going to be worried about it, (new mixes of old favourites). Part of what's happening now is a generational switchover: some people who are used to having things in stereo don't want to hear 5.1. But there are a lot of young people who love the home theatre experience and they're dying to hear more in surround.
Over reliance on the centre channel can cause reproduction problems when a home surround set-up uses poor quality loudspeakers or incorrect positions. If the lead vocal of a rock recording is mixed to the centre channel only, replay could become a ‘karaoke’ version with no lead vocal, or the vocal could be too loud or severely coloured through a low quality loudspeaker. Current consensus among audio producers from the pages of various industry magazines tends to favour traditional left-right phantom imaging with reduced amplitude centre reinforcement, usually only for sources that are centre panned like lead vocals, bass guitar and snare and bass drum. Chesky has been experimenting with a completely different approach. They believe that the centre and Low Frequency Effects channels are redundant in an ITU 5.1 system used for music only reproduction, and have instead repositioned the centre and LFE loudspeakers at around 55 degrees increasing the real width of the soundstage. In their recordings, they have captured acoustic reflections from these directions and reproduced it in the listening environment, with critical acclaim. This represents a departure from the ITU specification that may be difficult for many home listeners to implement physically, since it requires more amplifier channels and more loudspeakers. Chesky’s discs must also be clearly labelled so that consumers are not misled with incompatible product. Holman has also proposed delivering extra width and also height information, as the next development in aural immersion, but his system involves using ten channels for surround and height loudspeakers with two LFE sub-woofers, which is undeliverable using current technology. However, the idea of adding height information to enhance the horizontal dimension of 5.1 surround could be very exciting to sonic artists in particular, who are always seeking new opportunities to explore.
While deviations from the ITU specification for loudspeaker locations may be rich avenues for exploration, the focus of this paper has been on the possibilities offered by the original format. It is clear that there are many reasons why the chosen loudspeaker layout is not ideal for true aural immersion, with particular problems in the side and rear listening arcs. However, it is also very clear that there is now an audio standard that has been adopted by equipment manufacturers and embraced by consumers that has enormous potential to deliver an immersive and exciting aural experience. New delivery platforms including the Super Audio CD (SACD) and DVD-Audio offer improved audio quality for multi-channel reproduction. Software 5.1 encoders for DTS and Dolby Digital AC-3 are available for many music recording programs and as stand alone products. While there may be limitations, this should not deter audio practitioners from exploring the opportunities available today to expand listener’s appreciation of the aural environment. And as composer David Worrall remarked recently on an email list: For example, once one has achieved sounds whizzing around in 3D, what else is there to do with surround, compositionally speaking? The answer is: many things, beautiful, profound and delicate.
Epstein, Steven, 2000, "Orchestra Remains Up Front', Mix Magazine, August 2000, California: Primedia Inc. EQ Magazine, New York: Miller Freeman PSN, Ltd., monthly.
Mix Magazine, August 2000, California: Primedia Inc.
Holman, Tomlinson, 2000, 5.1 Surround Sound, Up and Running, Boston: Focal Press. ———, 1997, Sound for Film and Television, Boston: Focal Press.
ITU-R, 1993, Recommendation BS.775: Multi-channel stereophonic sound system with or without accompanying picture. International Telecommunications Union.
Steinmetz, Chris, "Percussion Power and Mystique", Mix Magazine, August 2000, California: Primedia Inc.
www.chesky.com