Speaker Cable White Paper

by: Michael Weizer, Director of Marketing, Accell Corporation

Introduction

When Accell set out to design our line of speaker cable products, we had two things in mind: Performance and Price. Our goal was to design a speaker cable that (1) would pass the critical listening tests of audio enthusiasts and (2) could be offered at prices that would make the cable accessible. To begin the study, the Accell team collected volumes of scientific data to develop a comprehensive understanding of the physical principles that govern human hearing. As experts in cable design, we then went straight to work to develop our family of UltraAudio speaker cables. In the following pages, we have provided a discussion of the most critical parameters and considerations in speaker cable design.

Human Hearing

The physics of human hearing can be distilled into a few guiding principles that relate to the audible frequency range and sensitivity of the human ear. Humans can generally hear sounds with characteristic frequencies between 20 Hz and 20 kHz (20,000 hertz). Bass frequencies lie at the low end of the frequency range (250 Hz and below). Instruments like the bass guitar and the bass drum put out the majority of their energy in this range. Instruments like the cymbal and flute, however, put out the majority of their energy at the high end of the frequency range (6 kHz and above). Frequencies within this range are commonly referred to as treble frequencies. Middle-frequency sounds (250 Hz to 6 kHz), also known as the midrange, are what most of us experience in our everyday lives. The most common examples of midrange sounds in music are vocals and guitars. In regards to loudness and hearing sensitivity, it is commonly known that except in carefully controlled laboratory experiments, the human ear cannot perceive a change of 1dB. Outside of the laboratory, a 3dB change is considered a just-perceivable difference. It is possible for an experienced listener to hear subtle sonic differences at or below 1dB, but the majority of listeners will not hear a difference.

What Makes A Good Speaker Cable

The "perfect" speaker cable is one that imposes no sonic signature on the audio signal that it carries. Because the laws of physics dictate that speaker cables cannot act absolutely neutral, good speaker cable design hinges on achieving as close to neutral performance as possible. The three most important factors to consider in cable design are copper quality, strand count, and insulation material. Discussions of each of these factors appear below.

1. Oxygen-Free Copper (OFC) - Copper wires are not all equal. Speaker wire conductors are commonly made of copper wire. Copper, although an excellent conductor, is prone to corrosion. Poor quality copper can corrode and deteriorate rather quickly to the point that it becomes noticeable in the speaker's performance. Just because your existing speaker cable hasn't turned green doesn't mean that your cable is safe. The effects of oxidation begin at the microscopic level and progressively deteriorate with time. Melting copper in an oxygen-free environment produces oxygen-free copper (OFC), which is ideal for use as a conductor in high-quality speaker wire. OFC resists corrosion and provides superior, long-term performance. Accell UltraAudio speaker cables use only high-purity 99.997% OFC cable.

2. Strand Count - Higher strand count leads to higher quality sound. Speaker cables typically consist of a twisted bunch of small wires. The reasoning behind this architecture relates to the fact that electrons in conduction travel at the surface of wires. Increasing the number of strands within a speaker cable increases the effective surface area for electrons to flow and decreases the probability of signal loss and saturation. Accell UltraAudio speaker cables use a high, 102-strand count OFC conductor that provides exceptionally low signal loss and excellent sound reproduction, even over long cable runs.

You may hear some cable companies argue that solid core conductors are superior to stranded core conductors because they eliminate "strand jumping", also known as the "strand effect". The strand effect occurs when electrons, while traveling in one single strand of a multi-strand cable, jump to another strand due to slight differences in electrical potential. Though the strand effect is indeed a measurable physical phenomenon, it is only a consideration at very high frequencies that are well beyond those of audio applications. In practice, stranded wire offers added benefit in that it is much more flexible than solid core wire making it more durable over time.

3. Insulation - A speaker cable's insulation (jacket) provides the cable with structural support while preventing a short between conductors. Cable companies use a variety of hydrocarbon-based materials and other synthetics for their insulators. Some use a fluorinated ethylene propylene (FEP) outer jacket (more commonly known as Teflon) that they claim provides significant improvements in performance. Be wary of cable companies selling you speaker wires with FEP jackets. Our studies show that the improvement in performance from using FEP jackets is negligible, often measuring less than tenths of 1dB. That level of improvement doesn't justify the premium price charged for these cables, particularly when the average listener considers a 3dB change just perceivable. Accell UltraAudio speaker cables use soft, transparent Polyvinyl Chloride (PVC) insulators that provide excellent flexibility and outstanding price-performance.