Part 6: Bi-Wired Loudspeaker Cables

Bi-wiring is running two lengths of cable between the power amplifier and loudspeaker. This technique usually produces much better sound quality than conventional single-wiring. Most high-end loudspeakers have two pairs of binding posts for bi-wiring, with one pair connected to the crossover's tweeter circuit and the other pair connected to the woofer circuit. The jumpers connecting the two pairs of binding posts fitted at the factory must be removed for bi-wiring.

In a bi-wired system, the power amplifier "sees" a higher impedance on the tweeter cable at low frequencies, and a lower impedance at high frequencies. The opposite is true in the woofer half of the bi-wired pair. This causes the signal to be split up, with high frequencies traveling mostly in the pair driving the loudspeaker's tweeter circuit and low frequencies conducted by the pair connected to the loudspeaker's woofer circuit. This frequency splitting reportedly reduces magnetic interactions in the cable, resulting in better sound. The large magnetic fields set up around the conductors by low-frequency energy can't affect the transfer of treble energy. No one knows exactly how or why bi-wiring works, but on nearly all loudspeakers with bi-wiring provision, it makes a big improvement in the sound. Whatever your cable budget, you should bi-wire if your loudspeaker has bi-wired inputs, even if it means buying two runs of less expensive cables.

You can bi-wire your loudspeakers with two identical single-wire runs, or with a specially prepared bi-wire set. A bi-wire set has one pair (positive and negative) of terminations at the amplifier end of the cable, and two pairs at the loudspeaker end of the cable. This makes it easier to hook up, and probably offers slightly better sound quality.

Loudspeakers can also be connected with a single bi-wire set in which a single cable with multiple internal conductors has two pairs of terminations on one end and a single pair of terminations at the other end. Although this approach is much less expensive than two runs of cable, you lose the benefit of magnetically isolating the low- and high-frequency conductors from each other.

Most bi-wired sets use identical cables for the high- and low-frequency legs. Mixing cables, however, can have several advantages. By using a cable with good bass on the low-frequency pair, and a more expensive but sweeter-sounding cable on the high-frequency pair, you can get better performance for a lower cost. Use a less expensive cable on the bass and put more money into the high-frequency cable. If you've already got two pairs of cable the same length, the higher-quality cable usually sounds better on the high-frequency side of the bi-wired pair. If you use different cables for bi-wiring, they should be made by the same manufacturer and have similar physical construction. If the cables in a bi-wired set have different capacitances or inductances, those capacitances and inductances change the loudspeaker's crossover characteristics.

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