70 Volt Speaker Load Calculator
Find your 70V system’s load & amp size
Use a 1kHz impedance reading if you’ve got a meter for it, or just add up your speaker tap settings if you don’t — either way, get the total connected wattage and the amplifier size you need.
Why 1kHz: every tap on a 70V transformer is rated in watts at 1kHz, so a 1kHz impedance reading converts straight to the total wattage every speaker on the line is set to draw.
Worth knowing: transformer impedance typically drops at lower frequencies, so bass-heavy program material can pull more current than this number suggests — that’s why the headroom below matters. A standard ohmmeter (DC resistance) is not an accurate substitute for a true 1kHz reading; it reads much lower and can mask real problems like a shorted line.
How to use this
- If you have a 1kHz impedance meter: measure across the line at the amp end (amp disconnected) and enter the reading.
- If you don’t: read the wattage tap each speaker is set to and how many are set to each value, and add a row per tap setting.
- Compare the suggested amp size to what you’re planning to install — if your amp is smaller than the total connected load, some taps won’t get full rated output.
Need a hand with the install?
Sound Solutions Inc. handles AV design, installation, and system tuning across southern West Virginia.
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