70V Line Speaker Wiring: Difference between revisions

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Similarly, we can apply a high voltage audio signal to a speaker line as long as there is a transformer at the speaker end to reduce the voltage to appropriate values for the drivers. Usually this system is used to distribute audio to a large venue with many speakers. In some cases, a constant voltage system is used to save money on speaker wire.

The reason the North American audio industry settled on 70 Volts is so all audio wiring can be installed without conduit. Many electrical codes of the time stipulated that voltages of 100 or more Volts must be installed in conduit. Modern codes break audio and signaling voltages into various classes. Class 2 covers typical speaker wiring installations. The main implication is that primary wiring and Class 2 wiring must never be placed in the same conduit or junction box. Note that the voltage is not ''constant,'' as its name seems to imply, but does actually fluctuate with the audio signal. The tapped transformer Power to the speaker voice coil reaches its rating when the speaker line Voltage reaches 70.

== Loudspeaker connection ==

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*Cost: The addition of transformers increases the cost of these speakers

*Frequency Response: Inexpensive transformers may have poor low and high frequency reproduction.

*Frequency Response: Inexpensive transformers may have poor low and high frequency reproduction. Primary applications for constant voltage systems are low fidelity paging and background music systems.

*Insertion Loss: As much as 20% of the amplifier's power is wasted through the transformers. This figure should be accounted for and compared to when calculating the losses encountered through various sizes of low impedance wiring.

*Capacitance: To handle higher powers, transformers have to be scaled up in size. The added capacitance begins to attenuate high frequencies.

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 Similarly, we can apply a high voltage audio signal to a speaker line as long as there is a transformer at the speaker end to reduce the voltage to appropriate values for the drivers. Usually this system is used to distribute audio to a large venue with many speakers. In some cases, a constant voltage system is used to save money on speaker wire.
+The reason the North American audio industry settled on 70 Volts is so all audio wiring can be installed without conduit. Many electrical codes of the time stipulated that voltages of 100 or more Volts must be installed in conduit. Modern codes break audio and signaling voltages into various classes. Class 2 covers typical speaker wiring installations. The main implication is that primary wiring and Class 2 wiring must never be placed in the same conduit or junction box. Note that the voltage is not ''constant,'' as its name seems to imply, but does actually fluctuate with the audio signal. The tapped transformer Power to the speaker voice coil reaches its rating when the speaker line Voltage reaches 70.
 == Loudspeaker connection ==
@@ Line 33: / Line 35: @@
 *Cost: The addition of transformers increases the cost of these speakers
-*Frequency Response: Inexpensive transformers may have poor low and high frequency reproduction.
+*Frequency Response: Inexpensive transformers may have poor low and high frequency reproduction. Primary applications for constant voltage systems are low fidelity paging and background music systems.
 *Insertion Loss: As much as 20% of the amplifier's power is wasted through the transformers. This figure should be accounted for and compared to when calculating the losses encountered through various sizes of low impedance wiring.
 *Capacitance: To handle higher powers, transformers have to be scaled up in size. The added capacitance begins to attenuate high frequencies.