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Where No Radio Has Gone Before

A Look Back at Surround's Development While Radio Was Avoiding the Technology

A Look Back at Surround’s Development While Radio Was Avoiding the Technology

(click thumbnail)Last issue we began a review of surround sound’s history, under the premise that understanding past processes is useful in predicting future outcomes. Today we’ll consider the helical road that surround sound technology has taken to arrive at today’s status, and how radio has been left out of the picture to date.

Remember that what we now call surround sound began life as quadraphonic sound, with its first incarnations appearing in the music industry, as described in the previous column. (For those really keeping historical score, the first “quad” music actually appeared in the soundtrack of the movie “Fantasia,” released by Disney in 1940, but this so-called Fantasound system used synchronized projectors – one for image, the other for sound – with three audio tracks sent to five speakers, three in front, two in the rear. It was never really commercialized beyond this single movie’s application.)

The death of quad

When we last left our heroes, they were valiantly engaged in a format war among three different quadraphonic release formats: SQ, QS and CD-4. The elegance of the 4-2-4 matrix approach shared by SQ and QS was a great advantage, but CD-4’s discrete quad technology was more impressive, at least under optimum conditions. This stimulated the matrix camp toward improved performance.

Next steps from these purveyors included smarter decoders such as Sansui’s Variomatrix for QS, and the Tate (or Fosgate) matrix for SQ, which sensed dominant signals in the program and reacted adaptively. These techniques, later generically referred to as “steering,” improved the effective separation between channels in matrixed signals during playback.

Even though these enhanced matrix decoders still didn’t match the separation of CD-4, the latter’s extreme demands on the vinyl medium and its less forgiving nature overall ultimately outweighed its potentially greater performance, and matrixed systems took the lead. UD-4, a “successor” to CD-4 developed by Denon and released briefly in Japan, never appeared in the United States.

The alliances formed by each record label choosing a quad format also played an important role in the format battle, with RCA being the only major label supporting CD-4 (remember it was developed by the associated JVC). While a few smaller labels supported the QS format, Columbia Records’ support of its affiliated CBS Labs’ SQ system, along with that of several other labels, allowed it to predominate.

Nevertheless, by the late 1970s consumer interest in quad overall had waned to the point that the form stagnated, and when the industry moved into digital technology with the launch of the CD format in the early 1980s, stereo was the only mode supported.

The post-mortem for quad cited numerous reasons for its demise. Most plausible were consumer confusion, lack of critical mass from the existence of multiple formats and the relative lack of quad content. Even the most supportive labels produced quad remix versions of only their most successful records in their catalogs, and released new quad recordings from just the most high-profile of their artists. At the height of the quad era, the vast majority of records were still produced and released only in stereo.

Another reason occasionally referenced for quad’s failure is its lack of any real traction in the radio business (remember FM stereo was itself still fairly new to many stations and listeners), and the fact that no broadcast technology specifically supporting quadraphonic reception was ever deployed.

Of course, matrixed quad could be passed through a stereo FM broadcast chain, and relatively successfully decoded by listeners equipped with the proper matrix decoder in their home listening systems; but there was never more than lukewarm support for this in the consumer electronics industry. Aside from a few “quad receivers” briefly marketed by a couple of manufacturers, listeners who wanted quad reception from matrixed content generally had to “roll their own” systems, using the fairly unwieldy arrangement of feeding a stereo tuner’s outputs to an outboard matrix decoder and then on to four channels of amplification and speakers.

The supersonic carriers on CD-4 records prevented passing their quad content through the ~15 kHz-limited FM system. Moreover, DJs disliked the format because of the audible sweep tone that its 30 kHz subcarriers produced as turntables came up to speed. These carriers also made CD-4 discs difficult to cue – almost impossible on songs that started quietly – because they were generally “on” throughout the disc even though they had no modulation during silence.

These issues, coupled with the overall dearth of quad LP releases, failed to stimulate radio broadcasters to air much quadrophonic content, which indeed may have assisted in escorting the form to an early exit.

Shifting the space

As we all know, however, matrixed quad resurfaced successfully in the cinematic environment.

In fact, for the next 20 years or so, the technology developed within the movie and TV-audio industries, not the music or radio environments. Quad became surround, and has only recently begun to reappear in the music and radio worlds.

This movement began in earnest as Dolby Labs licensed the same Scheiber matrix used by quad formats, adding its own twists for application to sound-for-picture in movie-theater sound systems, which began to appear in the mid-1970s. Instead of quad’s four-cornered box, Dolby reshaped the four channels as left, center, right and surround (L, C, R & S), where L, C and R speakers were all set as “front” sources placed behind the cinema screen, and the S channel was reproduced by multiple speakers distributed around the rear and sides of the theater, producing a diffuse effect from what was actually a single audio signal.

Dialog generally was assigned to the C channel to keep it centered to the picture, while music and sound effects were generally assigned to L and R (plus C when appropriate), with only ambience and reverb – and the occasional sound effect – assigned to S.

Dolby accommodated the relatively low level of audio in the S channel by band-limiting the high end of the S channel and adding Dolby-B noise reduction to it. (Remember that this was still deep in the analog era, and film sound generally was carried on optical stereo tracks printed in the same photographic process as the picture onto release prints.)

The results were welcomed warmly by the cinema industry and theater goers alike, and Dolby Surround, as the format was called, soon became the norm for major motion picture sound in theaters and 35 mm release prints. It also didn’t hurt that one of the first pictures released in Dolby Surround was “Star Wars,” and that film’s surprise runaway success, including its notable soundtrack and SFX, helped in the early establishment of the format.

Meanwhile, Dolby also developed a discrete six-channel magnetic audio format for theater sound, but this was limited to occasional blockbuster releases on 70 mm prints (which included a magnetic tape stripe coating alongside the film’s optical image area). This arrangement added a second surround channel (i.e., left surround and right surround channels, each still intended for reproduction via multiple speakers, but now wired as two separate sets on opposing sides of the theater’s side and back walls), and a dedicated “boom” channel for low-frequency effects (LFE, sent solely to subwoofers). Thus the channel lineup in this format was L, C, R, LS, RS and LFE.

This was the genesis of what we today call “5.1 surround,” which has since become standard in digital audio for video formats and is gradually working its way into the audio-only environment via such formats as DVD-A and SACD. (The six-channel format was ultimately renamed “5.1” because the LFE channel required only the lowest octave – occupying about one tenth the bandwidth – of the other full-range channels. More on digital surround next time.)

The much higher cost of 70 mm release prints and projectors relegated the six-channel discrete format to few films and theaters, so the matrixed optical Dolby Surround format became the method of choice for film soundtrack sound of the day. Its backward compatibility to legacy optical-projection and mono- or stereo-sound systems in theaters only increased its speed of adoption by filmmakers.

TV adopts what radio ignores

The popularity of matrixed cinematic surround meant that nearly all major motion pictures released since the late 1970s included such a soundtrack. Thus when Beta and VHS videocassette formats added stereo capabilities with their respective “Hi-Fi” upgrades in the early 1980s, video rentals and sales of movies began to include stereo soundtracks, which in turn included matrixed surround information.

This was not really an intentional feature, but simply occurred because the release prints used to master videocassette releases happened to include this encoding already in their optical stereo soundtracks.

The consumer electronics industry took great advantage of this circumstance, however, and consumer surround decoders began to proliferate. So began the home theater revolution, with easy access to the same Dolby Surround soundtracks that were once the sole province of movie theaters. As matrixed quad had done earlier, Dolby soon updated its consumer decoder designs with adaptive steering under the name of Dolby Pro-Logic, which provided much-improved imaging. A derived subwoofer output also was provided for more elegant bass management in home surround systems.

All the while, radio remained unaffected by this activity, and to this day lingers staunchly as a mono or stereo medium. In fact, Dolby Labs has placed limits on the licenses for its matrixed surround decoders intended to inhibit their use with integrated FM receivers, including all car audio systems. (To wit, while Dolby Surround does appear in some factory-installed automotive sound systems, it generally is limited to use with local playback sources, and is defeated when the tuner is selected.)

And even as radio broadcasters have considered their own conversion to digital broadcasting, the audio systems involved have been designed for stereo or mono use. Whether this will change is an item of ongoing current discussion.

Next time we’ll pick up the story of surround sound’s development with the entrance of digital audio and data compression systems, and take things to the current day’s consideration of a possible surround capability for radio at last.