Music CDs - Article No. 1 - April, 1996
By John Sunier
Although surround sound is today closely allied with home theater, it was, in the late 60's and 70's, strictly an audio buff's pursuit. Television viewers were buying into color and bigger screens, but the TV sound was generally limited to a single tiny speaker - usually with even less fidelity than the typical AM kitchen radio. In the meantime, hi-fi fanatics were bathing in musical sounds coming at them from all directions via the various competing quadraphonic formats on both LP and open reel tape.
Since few families can afford the space and expense of separate systems for a home theater and for strictly audio listening, an effort is being made today to convince consumers that a properly set up home theater sound system can add immensely to their music listening pleasure. Instead of the exaggerated four-cornered spatiality of both the quad equipment and most of the four channel demo recordings, we have today the more natural three-front-channels and one (or with AC-3 Dolby Digital and DTS's Coherent Acoustics, two) rear channels of Dolby Surround.
Over 15 million audio components containing Dolby Surround decoders have now been sold worldwide, and such processors are one of the biggest-selling items in home electronics. Even if music listening was not taken into consideration when a home theater system was selected and assembled, eventually the movie mavens will get around to using their system's built-in surround capabilities for straight music listening to CDs and other sources. Just about any stereo recording can provide at least some subtle surround effect, and this continuing column will be devoted to suggestions about music CDs of all sorts that will be especially enhanced via playback on a surround sound system.
The Introduction of Dolby Surround Music CDs
For some time, the Dolby personnel hesitated to license the use of their surround process - which was after all designed specifically for motion picture soundtracks - to be used with music CDs. But Producer Al Lutz, first at BMG Music and today at Delos International, persisted, and the first Dolby Surround music CDs came out on RCA Victor in l989. An initial release was "The Home Video Album" [Victor 60354-2RC]. This featured 20 selections from the Victor vaults remixed for surround effects using Dolby Surround encoding. The process is of course completely compatible for playback on standard two-channel stereo equipment. The album contains sections of studio fanfare music (a lot of nostalgic fun), intermission music, music for 40's films, for westerns, for sci-fi films, and even for silent films. Among the composers represented are Leroy Anderson, Max Steiner, Franz Waxman, Alfred Newman and Dimitri Tiomkin. There's even a discount ticket on your next purchase of popcorn (microwave type)!
Some of the most spectacular of the Victor Dolby Surround CDs are those remixed from original four-channel masters that were created with the idea of releasing on both open reel quadraphonic tapes and the long-abandoned, problematic CD-4 system (discrete four-channel sound on LPs). The best of these came from the Japanese synthesist Isao Tomita, who specialized in totally electronic versions of classical favorites. Among his surround CDs on Victor are "Holst: The Planets" [60518-2-RG], "Mussorgsky: Pictures at an Exhibition" [60576-2-RG], "Stravinsky: Firebird/Debussy: Afternoon of a Faun/Mussorgsky: Night on Bare Mountain" [60578-2-RG] and "Debussy: Snowflakes are Dancing" [60579-2-RG]. Tomita uses a fantastic variety of electronic and surround effects in these albums. Yet it's more than just the "see what I can do" stance of many of the early synthesizer albums. He has good taste mixed with a sense of good fun. Even the hackneyed "Planets" is a trip I wouldn't miss for anything. There is also a Victor surround series of new symphonic performances of great motion picture film scores by the National Philharmonic Orchestra conducted by Charles Gerhardt. Many of these also come from original four-channel quad masters. Having the pre-recorded quad open reel tapes of several of these allowed me the opportunity to make some comparisons between surround sound vintage l970 and surround sound of today.
As far as actual surround effects, there are audible losses in the transformation of the original four-channel material (with two discrete channels in the rear) into the single mono surround channel of Dolby Pro Logic Surround. This is perhaps more noticeable with the Tomita CDs since this performer used the quad layout in a creative manner, unlike most efforts at the time. However, there were down sides of the discrete quad open reel, compared to Dolby Pro Logic. First, most of the tapes were made before Dolby B noise processing was offered on open reel tape, so hiss intrudes in quieter sections. Then there was the high price of the pre-recorded tapes, and what seems today an unbelievable amount of just plain "fuss" to hear the tapes: Setting up the reel recorder, cleaning the playback heads of oxide deposits, rewinding the entire tape before you could play it (!), adjusting all the levels on your various amplifiers to match using a special test tone tape, etc. Shortly before the demise of the format, a few of the quad reel tapes came out with Dolby B encoding on all four channels. That meant two Dolby outboard decoders were required -- one for the front channels and the other for the rear!
Fortunately the Dolby surround decode circuit is a standardized thing - or at least it was until Dolby AC-3 came on the scene. In its latest version - Dolby Pro Logic - it is increasingly found as the only setting for surround sound on most surround components. I find this an unfortunate limitation of choices, since most Dolby Surround music CDs do not sound their best when played back via the full Pro Logic circuit with its electronic "steering" of sounds among the speakers. Only on some highest-end processors (in the $3000 area) have I found the steering to be accurate enough that one doesn't hear pumping or breathing artifacts when listening to Dolby Surround music CDs. (The Meridian 565 has my vote as the best decoding of music CDs.) It is also important to avoid the THX Pro Logic setting for music listening if you have a THX system. This special equalization "curve" is designed strictly for film soundtrack use and will roll off some high end on the front channels, making music sound dulled. In fact some THX home theater systems that were set up with only film viewing in mind may be extremely difficult to adjust for enjoyable surround playback of music-only CDs.
For best results with music, it is advised to select the plain Dolby Surround (non-Logic) setting if your component has one. Even better is the L - R ambience extraction setting, again if your component has one. Also known as the Haefler circuit, this may be called enhanced stereo, music surround, or something similar. Some THX processors have a Music or Stereo setting which completely mutes the center channel and the surround speakers for straight music listening, so watch out. This sort of un-enhanced stereo is fine for the audio purist who insists that "Two speakers is all I ever want," but you wouldn't be reading this if you fit that mold, would you?
The proper setting should feed only the difference information in the original signal to the rear speakers without any other processing, equalization, or digital reverberation. It would also be advantageous to have no 30ms delay signal, but some processors leave that Dolby requirement in the circuit for all the settings without the option of turning it off. The surround CDs reviewed here have been auditioned with an ambient surround sound decoder, as well as with an active music surround processor (Fosgate Model Four) using the "Classical" setting. There are three companies offering inexpensive passive or non-electronic L - R surround sound decoder boxes today. Two of them (Dynaco and the Chase Technologies HT-1) don't even require a separate amplifier, deriving that signal from your main stereo amplifier. The PhaseAround, on the other hand, has a line level in, and line level out, thus requiring another integrated or basic amp, but delivers a cleaner signal (less distortion).
A Thorough Surround Test CD
A good place to start is with a surround sound test CD. If you have even subtle level differences between the various channels - or worse yet - phasing differences, the surround effects on these CDs will be extremely useful. One of the best I've heard so far is "Surround Spectacular - The Music/The Tests" [Delos DE 3179]. This is a two-CD package, with Disc 1 presenting 21 short classical excerpts from the extensive Delos surround sound catalog. Some of the choral-orchestral selections are especially effective in surround, and even intimate instruments such as the Los Angeles Guitar Quartet benefit from the subtle feeling of the hall ambience that gives the performance in front of you an added realism and naturalness. The second, a test CD, opens with some surround sound effects that aptly fit the album's title. The steam locomotive passing in a thunderstorm was my favorite; shades of the hi-fi shows at the dawn of stereo! But the real meat of the project is the rest of the test tracks - there are 49 in total. Stereo Setup and Imaging work with the two or three front speakers. The wide and narrowband pink noise sounds are excellent for checking speaker imaging qualities and timbre differences between speakers. I was amazed at the slight timbre change from one side of my listening room to the other - due only to furniture, windows, and varying distances from the side walls - even though the speakers and their amps were identical. The closer the match of timbre and level among all the channels, the more transparent will be the surround soundfield. The timbral matching applies also to the speakers themselves. It is very difficult to get a seamless transition from your left front and right front speakers to the center speaker and to the surround speakers if all speakers do not have at least the same tweeters, and hopefully mid-range drivers too. Major differences here will stand out even more noticeably with straight music listening than they might with movie viewing.
Subwoofer Evaluation and Setup is the focus of the next part of the test CD. Achieving a smooth transition from your main speakers to the subwoofer is the purpose here, and this is not always a simple goal to achieve. An exaggerated level setting for the subwoofer may make action movies more exciting, but it can quickly make music sound ludicrous. Another useful contribution of these tests is provided by tracks with tone sweeps down to 20Hz. They can pinpoint noisy resonances at various spots in your listening room, and these objects can then be moved, tightened, or damped in some way. For example, at about the 30Hz point, the track of a lighting unit I recently installed began to buzz, and by tightening the screws I could easily eliminate the noise. Other tones pointed out that the mounting screws on all four of my subwoofer drivers had to be tightened a half turn or so.
The Surround Sound Setup and Imaging section asks you to set your processor for Dolby Pro Logic or Home THX for the tests. Again, these sounds will enable you to achieve a smoother transition and better balance between the various channels. Most processors have built-in noise generators for this purpose, but the Delos disc covers many finer points of setup. You may find you will get superior results if you try moving your speakers further out into the room away from the TV screen, or moving the left and right front speakers further apart from one another, or closer. Matching the rear speaker level to the front is another consideration. With most music listening, you should shoot for the surround speakers doing their job without drawing attention to themselves. In fact, you should really only be aware of the surround when it is turned off, unless you're listening to genuine spatial music, such as Tomita's electronics or the Berlioz Requiem. The effect should be of everything flattening out to the front of the listening area when the surround speakers are muted.
Other CD Sources of Surround Sound
It may surprise many readers that aside from the genuine multi-channel masters discussed above, most Dolby surround music CDs are produced not from three, four, or more channel originals, but from standard two channel stereo. (This is beginning to change with the advent of multi-channel DVD, and Delos new VR2 process is using up to six channels now.) The L - R difference information in the two channels is merely routed to the Dolby Surround channel of the matrix encoding process. The primary change that happens to that ambience signal occurs on playback if you use the Dolby surround setting on your processor. It is rolled off above 7 kHz in the treble and delayed about 30 milliseconds before reaching your surround speakers. If you select the Pro Logic setting, it is also steered in various ways, meaning the level is raised and lowered to pinpoint sounds more prominently either at one of the front speakers or the rear pair.
If you have a simple L - R ambience setting, you will find that although these Dolby surround music CDs sound very exciting, so do almost any standard well-recorded stereo CDs! If there is any stereo effect at all, there is some difference information in the signal. It is only some pop recordings built up from multiple "pan-potted" mono tracks or real-time pickups employing a forest of microphones that do not decode surround effects well. The LaserLight bargain label has a series of five-CD boxed sets mixing nature sounds with appropriate soft music. "Relaxation & Meditation with Music & Nature" is one of them [15 918]. The CD Caribbean Shores mixes the expected surf sounds with distant steel drums, while Amazon Rainforest has French horn and strings heard wafting through jungle bird and animal sound spectra. The ambient information on these discs provides plenty of material for your processor to chew on, and if you put your feet up and close your eyes, you will be completely bathed in the environment of your choice. An instant vacation!
Another LaserLight five-CD set is "Symphonies of the Planets" [15 925] This claims to be NASA Voyager recordings of the "sounds of the planets." They are very strong in the low-end, great for subwoofers and sci-fi fans. I can't speak for their authenticity, but these discs of 30 minutes each provide a unique alternative for those finding relaxation in such as whale songs, surf sounds, or Tibetan bowls. There has been a bit of audio trickery applied in the surround field; these recordings were processed with B.A.S.E.. This is a circuit that also plays around with L - R information, but with more gusto than a simple Haefler circuit. So the feeling of cosmic spaces and floating sounds in your listening room are further enhanced by the surround sound.
Next time we'll survey some pop and jazz CDs in surround sound.
� Copyright 1995, 1996, 1997 Secrets of Home Theater & High Fidelity
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