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Loudspeaker cables live in a strange electrical environment. Low impedance rules. They connect the low output impedance of a power amplifier often in the range of 0.1Ω or less to a still low impedance load. This speaker load is variable with frequency but rarely exceeds 30Ω. Though this impedance window is low, transients particularly in the bass can draw good current.
When using loudspeakers of average sensitivity whilst playing a highly dynamic piece of music, currents of 30 amps are no exception. From these working conditions it is clear that for a speaker cable resistance and inductance constitute the most important figures. With the low output impedance of the amplifier driving it, the cable’s capacitance is not really an issue. In general when a cable induces voltage loss due to excessive resistance or inductance, the sound quality goes down. The sound becomes dull and lifeless.
Cable resistance can be minimized by using multi-stranded conductors whose combinant surface area is neither too small nor large. Aside from wire geometry, termination factors into total resistance. A fine cable terminated with highly resistive connectors or equivalent solder can ruin the end result. Twisting wires and using half of them for the hot and the other half for the return is one way to exploit the magnetic field between the twisted wires to lower the cable’s inductance. Another is to use separate wires altogether which are of the best suited gauge for the job.
A conductor that grows too thick suffers from the negative influence of the skin effect where lower frequencies use the core of the conductor whilst higher frequencies migrate to the outer skin of the wire. When a single wire gets too thick to shift into the skin-effect zone, its total surface area is still smaller compared to a multi-stranded wire’s surface with the same cross-sectional area. Multi-stranded wire has simply more skin and a better skin-to-core ratio. With the wrong ratio, phase distortion enters due to impedance differences for the frequency ranges that use the core versus more of the skin. There thus should be the correct balance between cross-sectional and skin-surface areas.
Nanotec now have combined all the experiences of their ongoing development in the latest loudspeaker cable named SP#777 Great. Next to measurements a great part of the final development was carried out by the Golden Ears club where Takeshi Hayashi is a card-carrying member.
