Specifications

17
Speaker wire loss
A wire’s resistance is inversely proportional to the cross-sectional area of its conductor, but even the highest-
quality copper wire has some amount of resistance to electrical current flow. Therefore, to minimize the power
lost to speaker cable resistance, you should use the largest stranded (always stranded) copper wire that is
practical for the job. This is especially important with direct low-impedance speaker connections; e.g., a half-
ohm wire resistance would not affect a lightly-loaded 100-volt line noticeably, but it would reduce the amount of
power going to a 2-ohm load by 36%, a 1.9 dB drop. It would also reduce the damping factor to no better than 4.
If an amplifier could drive a speaker load through theoretical zero-resistance wire, no power would be lost in
the speaker cables. In the charts below we’ll compare the power delivered through real-world speaker cables
with the theoretical zero-resistance ideal and express it as a ratio called the power transfer coefficient. It is
determined by the formula
POWER TRANSFER COEFFICIENT = [R
LOAD
/(R
WIRE
+ R
LOAD
)]
2
Let’s say you have an 8-ohm speaker load. With that imaginary zero-resistance wire, all the power would be
delivered to the load, so the power transfer coefficient would be 1. If you then substituted wire with 0.2 ohm
of resistance, the load would only get 95.2% of the power it got with the zero-ohm wire, so the power transfer
coefficient would be 0.952 (a loss of 0.2 dB, by the way).