Relationship of power to speaker wire size?

Jfs

Standard Member
I have a question about speaker cables and power. What size (gauge) speaker wire do I need related to power of amplifier; wouldn't wire have to be a bigger gauge for more power or distance? I will probably not need more than 200 watts. Does anyone know of a chart?

Thanks
 
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Alan Mac

Active Member
I have a question about speaker cables and power. What size (gauge) speaker wire do I need
related to power of amplifier; wouldn't wire have to be a bigger gauge for more power or
distance? I will probably not need more than 200 watts. Does anyone know of a chart?

The resistance of a wire conductor is inversely proportional to its cross-sectional-area.

The rate of energy loss [the power loss (P)] in a cable is proportional to the resistance (R) of the conductors and to the square of the current (I^2) flowing through them.

P = I^2 x R

The I^2 xR loss is of great importance for electrical energy distribution and is the reason for using as high a voltage as possible (to minimise the current required).

However, the power loss in a loudspeaker cable is not normally of any consequence.

[A 1 mm^2 copper conductor can easily carry 10 A continuously.

In a load of 8 Ω , 10 A continuous results in an energy transfer rate of 800 W.

For a typical audio signal, the continuous average power will be about 1% of the peak power. So the 1 mm^2 copper conductor can cope with the full output from an 80 kW rated amplifier when driven with a real-world audio signal.

So the amplifier power is irrelevant when deciding what gauge of wire to use]


What does matter is that the resistance of the conductors should be small compared with the impedance of the loudspeaker otherwise the loudspeaker impedance variations with frequency will cause variation in the magnitude-versus-frequency response of the overall system.

As a general rule of thumb, the loudspeaker cable conductor resistance should not exceed 5 % of the nominal impedance of the loudspeaker it is connected to.

So for an 8 Ω loudspeaker the cable conductor resistance should be less than 400 mΩ.

Here is a useful calculator relating wire gauge to resistance.

ePanorama.net


Alan
 
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