Free tool
Speaker impedance calculator
Add your speakers, pick series or parallel, and get the total load in ohms. If the result dips below a safe amplifier load, the tool flags it. Free, and nothing leaves your browser.
Total load impedance
4 Ω
Assumes a nominal impedance per driver. Always check your amplifier's minimum-load rating before wiring.
Wire more than one speaker without smoking the amp
Put several speakers on one amplifier channel and the load it sees changes. Wire them wrong and the impedance drops too low, the amp overheats or clips, and in the worst case something fails on site. This calculator gives the exact total so you can match speakers to an amplifier that is rated for the load.
Series vs parallel
- Series adds up: two 8 Ω speakers in series = 16 Ω.
- Parallel divides: two 8 Ω speakers in parallel = 4 Ω; four 8 Ω = 2 Ω.
- Most amplifiers are rated to a 4 Ω minimum, some two-channel amps to 2 Ω.
For 70V/100V line systems you tally wattage taps instead of impedance. Spec'ing a full audio install? Avitly keeps speakers, amplifiers, and cable on one plan so the load you calculate here is the load you quote.
Common questions
What happens if the impedance drops below my amplifier's rating?
The amplifier tries to deliver more current than it was designed for. Best case its protection circuit engages and the channel mutes; worst case the output stage overheats and fails. Most amps rated at 4 ohms will not survive a sustained 2 ohm load. Always check the total before powering up, not after.
How do I calculate speakers wired in parallel?
For identical speakers, divide one speaker's impedance by the number of speakers: four 8 ohm speakers in parallel give 2 ohms. For mixed impedances, add the reciprocals and invert the result. Parallel is the common wiring for ceiling speakers on a low-impedance run, which is exactly why the total drops so fast.
How do I calculate speakers wired in series?
Add the impedances: two 8 ohm speakers in series give 16 ohms. Series raises the load, which is safer for the amp but costs power and means one failed driver opens the whole circuit. It is rarely used beyond pairs for that reason.
Should I use 70V/100V instead?
For anything more than a handful of speakers, yes. A constant-voltage line uses a transformer on each speaker, so you budget by wattage tap rather than impedance, and you can hang dozens of speakers on one run without the load collapsing. Low-impedance wiring is for short runs with few speakers, typically a stereo pair or a small zone.
Why is a speaker's rated impedance not what my meter reads?
Rated impedance is a nominal figure. Real impedance varies with frequency, dipping near resonance and rising with the voice coil's inductance, and a DC meter reads only the coil resistance, typically around 6 ohms on an 8 ohm driver. Use the nominal rating for load calculations; that is what amplifier ratings assume.
Can I mix speakers with different impedances on one amplifier channel?
Electrically yes, and this calculator handles it, but power splits unevenly: the lowest-impedance speaker draws the most current and plays loudest. If you need matched levels, keep impedances the same or move to a constant-voltage line where each tap sets its own wattage.
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