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10 Matica 500/900 Reference Manual
multiple loudspeakers or systems to any amplifier, care should be taken that the
actual load impedance does not drop below the amplifierÕs rated output load.
Alesis amplifiers will not be damaged by excessively low output load impedances,
but they will not be able to provide full output power and their protection circuits
may automatically cut off their outputs until the low load condition is removed.
Gauge Diameter DC Resist./ Cable Length Resulting in a 1 dB Power Loss
(AWG) (Solid) 30 m (100Õ) 4 W Load Impedance 8 W Load Impedance
6 4.12 mm 0.08 W 366 m 1200Õ 740 m 2400Õ
8 3.26 mm 0.13 W 244 m 800Õ 488 m 1600Õ
10 2.59 mm 0.20 W 145 m 475Õ 290 m 950Õ
12 2.05 mm 0.32 W 91 m 300Õ 182 m 600Õ
14 1.63 mm 0.52 W 58 m 190Õ 116 m 380Õ
16 1.29 mm 0.82 W 37 m 120Õ 74 m 240Õ
18 1.02 mm 1.32 W 23 m 75Õ 46 m 150Õ
20 0.81 mm 2.08 W 15 m 50Õ 30 m 100Õ
22 0.64 mm 3.30 W 9 m 30Õ 18 m 60Õ
Table 2: Speaker Cable Losses. Values are calculated based on the sum of the length of both
conductors. Note that a 1 dB power loss is equivalent to 12% of the amplifier power.
The wire thickness or gauge should be chosen according to the load impedance and the
length of the wire run from the amplifier to the loudspeaker terminals. See Table 2.
Because the wireÕs resistance to the flow of current is in series with the
loudspeaker, a wire with lower resistance will deliver more power to the
loudspeaker; also, the amplifier will be able to control the loudspeakerÕs
movement betterÑthis latter is called Òdamping factor.Ó
ItÕs interesting to observe that an amplifierÕs rated damping factor is essentially
unrealizable unless the loudspeaker is connected directly to the amplifierÕs output
terminals without any interconnecting cables. For example, a typical installation
using 20 feet (6 m) of 16 AWG wire connecting an amplifier and an 8 ohm speaker
will result in a damping factor of 23.5 with a perfect amplifier; with a real world
amplifier, the damping factor will be even lower.
Many special cables are sold for use with audiophile and studio loudspeakers. We
make no recommendations for cables other than that there be sufficient copper in
them to keep the total resistance acceptably low.
Loudspeaker outputs for both channels are on heavy-duty five-way binding posts
which can accept single or dual banana plugs, bare wire or terminals. See Figure 2
above. Note the unique in-line configuration of these binding posts.