70-Volt Systems Cable Size, Length
2 min readCable Size / Length vs Power and dB Loss
When deciding on which speaker cable type to use for your application you will need to consider the cables “guage” and “distance” requirements. The chart below shows Cable sizes vs. Power and dB losses in the cable.
Let’s look at an example using the chart below:
- At 4-ohms / 18-gauge cable can be run 120 feet and will realize a 50% / 3dB loss on the line.
- At 8-ohms / 18-gauge cable can be run 235 feet and will realize a 50% / 3dB loss on the line.
- 70 Volt Systems have very high impedances, so at 70-Volts an 18-gauge cable can be run 5600 feet in order to realize a 50% / 3dB loss on the line. This is one of the main advantages of using a 70V system – being able to run a cable a couple hundred feet away and not realizing any significant loss on the speaker line.
- Reminder: The calculations in the chart below are not exact (only approximated for demonstration).
Looking at the chart above you can see that 70 Volt speaker lines have very little Power / dB loss over longer distances than those of 4-ohm or 8-ohm speaker line distances. This is one of the advantages of Constant Voltage Systems. Using 14AWG size cable can function properly up to 15,000 feet (not sure how many systems run a cable this long but it’s interesting to note.
In my experience, we mainly used 70V systems since our installations were mostly on Rides / Large outdoor spaces. Ex: We would install 70V speakers every 8-10 feet all the way up a 200-foot lift, and it worked great every time.
