How to Wire a 70V Speaker


A 70-volt audio distribution system is used more often in offices, churches and industry than in homes, but can be used in multi-room home systems fed by a single amplifier setup and audio feed. Speakers used with such systems are generally ceiling or wall-mounted and do not necessarily operate on 70 volts. Mounted on one leg of the speaker basket, a small matching transformer that transforms the speakers' 8 or 4-Ohm impedance to high impedance allows them to be used in large numbers attached to a special 70V distribution amplifier. Each room usually has a stepped volume control.

Things You'll Need

  • Speaker wire
  • 20-Gauge wire nuts
  • Cutting pliers
  • Wire strippers
  • Locate the black and brown primary leads coming from the speaker's transformer. These are usually pre-tinned.

  • Measure how long the speaker wire from the room attenuator to the speaker should be and leave about two feet of slack on both ends. Since current is low up to the speaker transformer, 20-gauge wire is sufficient.

  • Split about six inches of wire on both ends and strip 1/2 inch of insulation off each lead.

  • On the speaker end, use wire nuts to connect the copper-colored lead of speaker wire to the brown primary wire of the transformer, and the silver-colored lead to the black primary wire.

  • On the attenuator end, locate the "out" screw terminals.

  • Twist together the strands on each speaker wire lead and bend each end into a loop. Attach the silver-colored speaker lead under the "common out" screw terminal and the copper-colored lead under the other "out" terminal.

  • To connect the attenuator to the distribution amp, run the negative lead of the speaker wire between the amp's common output tap and the attenuator's common input terminal, and the positive lead between the amp's 70V output tap and the attenuator's input common tap. If you are attaching more speakers in other rooms, daisy-chain speaker wire between attenuator input taps. If you are installing stereo, each channel requires its own wire and attenuators.

Tips & Warnings

  • Speakers meant for 70V installation are already wired to their pre-mounted transformers.
  • Ganged stereo attenuators are available for stereo installations.

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  • Photo Credit Jupiterimages/ Images transformateur électrique image by Lounatiq from
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