Installation manual

Community S-Series - Operation and Installation Manual - Page 29

Below is a table that gives a quick look at the effect of wire size on line loss. These

numbers assume that the amplifier is producing a constant 48 Volts at its output terminals,

which is equivalent to 288 watts into 8Ω or 576 watts into 4Ω:

Size Length Load Z Loss in dB

#10 AWG 100’ 8Ω -0.42 dB

#10 AWG 200’ 8Ω -0.83 dB

#10 AWG 100’ 4Ω -0.83 dB

#10 AWG 200’ 4Ω -1.58 dB

#12 AWG 100’ 8Ω -0.66 dB

#12 AWG 200’ 8Ω -1.28 dB

#12 AWG 100’ 4Ω -1.28 dB

#12 AWG 200’ 4Ω -2.39 dB

#14 AWG 100’ 8Ω -1.03 dB

#14 AWG 200’ 8Ω -1.95 dB

#14 AWG 100’ 4Ω -1.95 dB

#14 AWG 200’ 4Ω -3.55 dB

The worst-case scenario shown above is the 200’ run of #14 AWG into a 4 ohm load. This

will result in a staggering loss of -3.55 dB, or more than half of the amplifier’s total power

output. Use of wire that’s one size smaller, #16 AWG, would cause a power loss of -5.11

dB. As you can readily see, it’s very important to use the largest gauge wire that you

possibly can, particularly when long lines are unavoidable. NL4-compatible connectors can

easily accept #12 AWG.

C-TIP: When choosing cable for a situation that requires only two conductors, consider

using 14/4 (that is, #14 AWG with 4 conductors) and wiring each pair of conductors in

parallel, at both ends of the cable. This will provide the equivalent conductance of #11

AWG, but in a cable that’s more easily obtainable and smaller in diameter.

The Effect of Wire Gauge on Damping Factor

As significant as power loss can be, the effect of wire resistance on the damping factor of

the loudspeaker/amplifier network is even greater for a given resistance value. (For a

description of Damping Factor, see page 32)

Amplifier designers intend for the output impedance of their amplifiers to be as low as

possible, in order to achieve a high damping factor. However, the laws of physics dictate

that a very low output impedance will cause the resistance of the speaker cable to have a

significant effect on the amplifier/speaker network. Unfortunately there’s no way to get

around it.

Example: With five feet of #10 AWG feeding a 4 ohm load, a given amplifier exhibits a

respectable 100:1 damping factor. With fifty feet of #10 AWG feeding the same 4 ohm

load, the damping factor decreases to 10:1, which is likely to be audible as a loss of ‘punch’

and tightness in the low frequencies.

Unless the power amplifiers are located directly alongside the loudspeakers (a good design

technique to consider when possible), it will be difficult to maintain a high damping factor

without using impractically large conductors. Therefore, keeping cable lengths as short as

possible, is the most practical and cost-effective way to maintain a respectable damping

factor without incurring undue difficulties.