Philosophical and Pragmatic
Approaches to Stereo
The first three chapters have focused on the various physiological, acoustical, and psychoacoustic parameters that form the basis of stereophonic perception. The technical procedures employed to produce today’s stereo sound recording and reproduction process will be discussed in subsequent chapters. All of these are tangible elements involved in the creating the stereophonic illusion and all are solidly grounded on scientific principles of physics, acoustics, and biophysics.
Before any recording project can begin, however, certain fundamental decisions need to be made — decisions that will indicate the format, style, and even the procedures implemented during the recording process. Some of these decisions are dictated by the content or style of the subject to be conveyed, for example: music, speech, sound effects, etc. Other, more pragmatic factors considered at this stage include: whether the recording/reproduction process is intended to be solely an auditory experience, or will it combine sound with picture; the medium of the recording — commercial record release, radio or television broadcast, film, etc.; the mode of the project (entertainment, documentary, sports or news, etc.); and the anticipated reproduction or listening environment.
These fundamental decisions will determine how a recording project is to proceed, and many of them will be based on more intangible factors such as mood, feeling, and intuition than on scientific fact. Thus science and philosophy must go hand in hand in the creation of the stereo illusion.
The Five W’s
All writers know that for any idea to be communicated effectively The Five W’s should be addressed: Who, What, When, Where, and Why. These five considerations are equally important to the process of making a recording. After all, sound recording is really just another medium of communication — a means of expressing an idea aurally rather than visually.
• Who is the listener? Is he/she experienced in the subject of the recording? Is he/she a “critical” or a “casual” listener?
• What is the medium? Is it a purely auditory one such as a cassette, compact disc, or the radio, or does it also involve pictures, such as film or television, multi-media, or DVD?
• When is he/she listening? Does the listening experience occur in the background or foreground of the listener’s attention?
• Where is the listening environment? Is it at home, at work, in an elevator, a theatre, while jogging, or in a car?
• Why is he/she listening? Is it for the pleasure of the experience, for information content, or simply for entertainment?
The answers to each of these questions contribute significantly to the determination of how the recording should proceed. Some factors can be complementary, while others prove to be mutually exclusive. The technical procedures employed, however, must be compatible with all of these dictates. A producer even might decide that more than one answer is appropriate to each of the questions, possibly forcing a compromise between various technical procedures.
Recreating an Event
To initiate the decision-making process, the flavor of the recording first must be determined. This “flavor” establishes the essential listening experience that the producer, performer, and/or engineer wants to convey to the listener. A recording is, by its very nature, an artificial substitute for a “live” experience — reality — and can never be expected to equal the essential qualities inherent in “being there.” The best any recording can attain is a reasonable simulation of the live experience; this simulation can be derived from two related, although nonetheless quite different, philosophical approaches to the recording process: “Recreative” and “Creative.”
As the term “recreative” implies, this philosophy of recording intends to recreate a sonic experience for listeners in their own environment. The purpose is to make listeners feel that they are listening to a real event — something that actually happened, or could have happened — that has been transferred in time and/or space and transported into their presence via the recording process. This requires that all sense of the event’s realism must be captured and retained, so that listeners will feel as though they are participants at the event. Concerts, sporting events, news and documentaries are among the sonic events most appropriate to this recording philosophy.
Technical procedures for recreative recordings generally involve what are sometimes called “purist” microphone techniques (as will be discussed in Chapters Five, Six, Seven, and Nine) and uncomplicated recording methods to try to maintain the original ambience of the sonic space. These generally offer minimal alteration of the sonic perspective of the original event.
Creating a New Event
“Creative” recording brings to the listener an experience which never happened in “real time,” but which the creators of the sonic illusion would like to have happened. As before, the intent is to make listeners participants at this sonic event — even though this might be impossible to achieve in the “real world.”
When creating a listening experience, applicable recording techniques allow considerably more experimentation, so that multi-microphone, multi-track procedures are more commonly utilized. Significant signal processing, synthesis, and artificial ambience are also employed to create a new, unique listening experience.
Some believe that these two approaches to expressing a sonic image — “Creative” or “Recreative” — are one and the same. This stems from the concept that the two are merely alternate means of observing an event and conveying its essence. The fundamental belief here is that the illusion can never equal the reality, because the only true reality is being there. In the context of recorded sound, however, reality is what you make of it.
The Listener’s Perspective
The listener’s aural “viewpoint” of the recording also can be described by two contrasting sonic perspectives, which are often called “You Are There” or “They Are Here” (In this context, “you” refers to the listener and “they” are the performers.) When considering the listener’s perspective, the differences between the approaches are more distinct than the styles of creating a listening experience.
With “You Are There,” the intent is to generate an aural perspective which will transport the listeners into the same sonic environment as the event — to put the listeners into the audience, as it were. This approach is appropriate to almost any form of real sonic event, and lends itself particularly well to concerts, certain sporting events, dramatic or documentary presentations, environmental scenes, and the like.
On the other hand, “They Are Here,” as the name implies, attempts to bring the sonic event directly to the listener, and reproduce it in the listening environment. This approach is only plausible when the sonic “illusion” could logically be happening in this listening space. Hence, a major league ball game, large symphony orchestra, or recreation of “the Battle of the Bulge” would not be convincing, whereas a ping-pong match, a string quartet, or even a fist fight between two individuals might be.
The “Two by Two” Matrix
The style of the reproduction can be correlated with the viewpoint by placing them both into a simple two-by-two matrix. If the top is labeled according to philosophy and the sides according to perspective, it is possible to derive four distinct approaches to the recording and reproduction of a sonic experience. These prove to be the logical result of the experience itself. (Table 4-1)
Both “You Are There” and “They Are Here” recordings can be either recreative or creative, depending on the sonic illusion desired. The various technical means to accomplish these styles can differ from one to another, which can be shown by expanding the contents of the matrix to include some of the relevant production techniques employed for each approach. (Table 4-2)
The matrix implies that although there are four initial directions a recording project can pursue, within each are several “alternate routes” which the producer or engineer also could follow. Once the primary course has been determined, however, it should be followed to its final destination. Sudden or abrupt deviations from the chosen course might distract the listener or lead to confusion — whether conscious or subliminal — and thereby destroy the illusion. If the listener becomes aware of the techniques employed to make the recording, the program content will be pushed into the background, rather than remain the focus of attention. (Similarly, in the theatre, if the lighting effects or staging draw the attention of the viewer away from the story line, the essence of the play will be lost.)
Various technical constraints inherent to the recording and reproduction medium also play an important role when determining the processes to be used. These considerations are not only the practical limitations of the recording format (such as amplitude, dynamics, phase, spectrum, and distortion), but also such factors as the number of transmission channels, the placement of loudspeakers in the listening environment, etc.
The amplitude limitation relates to the absolute signal level inherent with the recording and playback medium. Recording techniques intended for digital audio production allow significantly greater freedom of choice to the recording engineer than techniques used for cassette or AM radio broadcast, where the signal level and dynamic range are significantly more restricted.
Related to amplitude, the dynamic range of a recording defines the extremes between loud and soft. Like the absolute limit on amplitude, these extremes also must be considered in context with both the sonic material and the listening environment. For a recording to equal the impact of a live concert, for example, the playback must be at a sound pressure level near to what the listener would experience in the concert hall. This has obvious limitations in the practical world where the problems of home playback equipment, consideration for the neighbors, and other factors will restrict the playback volume to a more conservative level. (This relates back to the where and when discussed under “The Five W’s.”) Nonetheless, a recording must be able to preserve the impression — even if not the full extent — of the dynamic range of the original, or the emotional impact will be diminished. After all, a full symphony orchestra, a heavy metal band, or even a competent singer can easily overpower the acoustical capacities of a small apartment.
In Chapter Two, listening cues exhibiting interchannel amplitude and time-of-arrival (i.e. phase) differences between the two stereo channels were shown to be crucial to determining our perception of stereo space throughout the entire frequency spectrum. Thus, when considering the integrity of the stereo image, a critical technical factor is phase coherency between the channels. If the production introduces contradictions between the amplitude and phase cues in the stereo signal, serious image confusion could result. Therefore it is of primary importance to retain consistent amplitude and coherent phase response throughout the entire recording/reproduction process, regardless of the ultimate medium of distribution.
Although relative amplitude, spectrum, and dynamic range all can be compromised to some degree without causing serious deterioration of the stereo image, improper attention to phase coherency during the original recording process will produce a flawed recording from the outset, which cannot be corrected later. Therefore, the implementation of proper microphone techniques is crucial during the original recording stages, and these must be chosen to be complementary to the style of the recording and the demands of the distribution medium.
Spectrum is a technical term which describes the texture of the waveform of all individual sounds — defining their “sonic identity.” Timbre is another, more musical name for spectrum. Although the two terms are not identical (spectrum represents the physical attributes of a sound, while timbre generally refers to the more subjective perceptions of these attributes), they are closely related because the preservation of spectrum is essential to the accurate reproduction of timbre. Throughout the recording and reproduction process, careful preservation of the spectral integrity of the sound is necessary to maintain the proper illusion for the listener.
Distortion is the primary enemy of spectrum because distortion generates unwanted alterations to the sonic fidelity of the audio chain. It can affect any or all of the previous technical factors, and its insidious effects can be introduced anywhere in the long progress from performance to listener.
Distortion can take two forms: linear or nonlinear. Linear distortion simply produces changes in the amplitude and phase response of the audio signal, but without adding anything else to it. Nonlinear distortion, however, creates new, unwanted components and adds them to the audio signal. These components can be either harmonically or non-harmonically related to the original signal, and are quite audible even at relatively low levels compared to the original signal. Thus, nonlinear distortion is generally considered much more annoying to the listener than linear distortion.
Although these technical considerations are not inherently part of the philosophy of the recording process, they must, nonetheless, be considered during the earliest planning stages because they interact with the philosophical factors. A comparison of the technical parameters with the various distribution formats can be shown by placing them into two columns, as in Table 4-3. (Please understand, however, that these are not meant to imply directly parallel comparisons.)
Each of the different recording formats listed in Table 4-3 imposes its own technical limitations on the recording/reproduction process. As an example, the cassette format places greater constraints on the recording process than does a compact disc or even a phonograph record. All technical parameters — amplitude, phase response, dynamic range, distortion, and spectral content — have fairly narrow limits and should be considered carefully when producing an original recording intended specifically for cassette distribution.
However, if the same recording is to be released as a compact disc (a medium which does not pose these same restrictions) should the original recording be compromised for the sake of the cassette? Of course not. The proper procedure is to make the initial recording suitable for the compact disc and then use this full range recording to produce another, more controlled master suitable for cassette duplication. The rule of downward — or upward — compatibility is to preserve the absolute integrity of the original material as far into the recording/reproduction process as possible.
A similar comparison can be drawn when considering, for example, a compact disc recording which will subsequently be broadcast. Usually, the constraints necessitated by the broadcast medium are imposed by the radio or television facility itself, whose signal chain incorporates special signal processing devices to restrict dynamic range, spectrum, etc. With many radio stations, such manipulation of the original program signal is determined as much or more by their own “on-air sound” (philosophical considerations) as by fundamental technical constraints.
Next, suppose a recording is to be made by the broadcast facility’s own production staff, perhaps initially for air, but reserving the option for subsequent release as a compact disc or other format. Should the recording be made preserving full spectrum, with maximum separation and dynamic range, or should the recording team constrain these factors to suit the limitations of the broadcast medium or the station’s particular “sound”? Ultimately, this decision will be made by the program’s producer, who might choose to tailor the original recording to suit the station’s particular sound, thereby limiting further use of the material. Alternatively, he/she could retain full options for future use of the recording and leave any technical constraints subsequently in the hands of the broadcast engineer. Both attitudes are valid, but the decision must be made at the outset.
Sonic and Visual Images
When assessing the impact of television on the dwindling radio audience, someone once quipped: “Yes… but radio has better pictures.” While this implies the importance of the listener’s imagination, this also is a direct reference to the concept of the Sonic Illusion. The point is that the visual images presented by television (or film) dictate to us precisely what we, the viewer, will see, and therefore constrain our imaginations.
When producing sound with pictures (television or film) severe restraints are placed on the sound department to maintain a sonic perspective that will complement the visual image. (Chapter Thirteen discusses more fully the various perspectives available for sound with pictures.) If the sound editor wishes to withhold editorial decision over the sonic image until the picture has been cut, this dictates certain microphone and recording techniques which can afford this degree of flexibility during the rerecording mix.
The introduction of visual images introduces media-imposed restraints on the purely audio component of the program, because the pictures dictate just what the sonic perspective must be. The recording engineer is no longer free to create an autonomous sonic image. “You Are There” becomes the only possible attitude, and you, the listener, are limited to being a spectator of the event, rather than a participant.
The “Law of Compromises”
It is important to reemphasize that the basic approach to making a stereo recording must be decided at the outset of the project, and this will be determined by the several, often competing, technical and philosophical factors involved. This decision process acknowledges the Law of Compromise inherent throughout the world of audio.
This law, although not written anywhere is universally imposed nonetheless. It dictates that any decision with regard to the production or reproduction of a recorded experience must result from a choice among compromises. Simply, this means that what is best for one set of circumstances likely may sacrifice others. It is the charge of the producer to select from among these compromises those that will be the most beneficial — or, stated another way, the least damaging — to the final product. Although this may seem a rather cynical viewpoint, it is merely simple pragmatism.
In the end, the choice is between illusion or reality… you can’t have both.