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The active components of an audio system (such as the tuner, amplifier, CD player, or tape deck) are directly and logically linked to its ultimate sound quality. But there has also been considerable promotion of such passive “components” as interconnect and speaker cables, including claims that they, too, have a substantial effect on sound quality. Actually, “substantial” is a rather mild adjective in the vocabulary of cable advertising. I don’t propose to get too involved in that morass. A recent announcement by Lucasfilm that it has established a set of specifications for certified Home THX interconnects and speaker cables seems to invest the subject with more authority, however, and when you examine Lucasfilm’s rationale for standardizing Home THX interconnects—to insure trouble-free connections between the components of a Home THX system—the logic is indisputable. For example, the recommended standards for a multipin, six- channel interconnection system, de signed for use with controllers, amplifiers, and equalizers, cover color coding, general electrical performance, and mechanical characteristics such as cable flexibility, insertion and removal force, connector diameter, jacket friction, and termination quality. I cannot argue with the importance of such standardization when dealing with a complex multi-component and multichannel system such as a full-blown Home THX installation. There is already a degree of standardization in the interconnection of home audio components, in the form of the phono jack and plug. There is little, if any, standardization of the cable itself, however, nor is there much need for it in a basic stereo system. Most components are designed to be relatively independent of their load impedance over a wide range of capacitance and inductance, and such deviations as may arise from the cable interface are almost never audible. Note that Lucasfilm does not mention sound quality (other than an absence of audible hum, noise, and distortion) as a benefit of adherence to the Home THX cable standards. There are a number of manufacturers of premium audio cable, and some of their products (probably most of them, in fact) are truly excellent with respect to their mechanical properties. I use them myself—not in a music system, but for testing loudspeakers, where their physical ruggedness, flexibility, and low resistance make them the logical choice. My test needs are rather special, though. What about the advantages of such high-price cables in a normal, fixed installation? If I knew of any, I would certainly speak up, but by and large they do nothing that an ordinary twin-conductor wire could not do at a small fraction of their cost. But don’t they improve the sound? That is the essence of the benefit claimed for most exotic cables—a vaguely expressed or indefinable improvement in sound quality that is said to justify an additional investment of hundreds (or thousands) of dollars. A speaker cable has only three significant electrical properties: resistance, capacitance, and inductance. For low-level interconnects, there is also shielding to be considered. That is it—absolutely nothing else can affect a cable’s operation in a properly functioning audio system, although some cable companies do try to suggest that real-world audio cables can have problems with impedance mis matching or “skin effect.” Pure nonsense! As it happens, some exotic cables actually have an excessive amount of inductance or capacitance, and some poorly designed amplifiers can become unstable when driving such a reactive load. So what about the claimed sonic improvements so often attributed to special speaker cables? When the claim is made by the cable manufacturer, the reason is obvious and re quires no explanation. In other cases, it is probably a manifestation of the power of positive thinking: people deluding themselves into thinking that they are hearing something because they have been told by an “expert” that it is there (the “Emperor’s new clothes” syndrome). Since hearing is ultimately a mental function, they are probably happy in the thought that a sizable investment in system cables can reap a harvest of improved sound. It has been said that “hearing is believing.” The reverse is often equally true, that believing is hearing. Actually, there is one way that a cable can affect the sound without magic or hypnosis. All amplifiers have an internal resistance (their “source impedance”) that is effectively in series with the loudspeaker load. Though normally negligible, the source impedance can combine with the load impedance to modify the system’s frequency response by impressing the shape of the speaker’s impedance curve on its frequency response. Except with tube amplifiers, which have output transformers that raise their source impedances relatively high, this effect is almost always small, but critical listening can reveal it. Just re member: This effect is normally only a minute change in frequency response—hardly a matter to be concerned about unless you are the type who agonizes about how many angels can dance on the head of a pin. Source: Stereo Review (Jan. 1994) by Julian Hirsch |
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