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Speaker Impedance Calculator

Total Impedance for Speakers in Series, Parallel or Mixed Wiring, Checked Against Your Amp

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How the Speaker Impedance Calculator works

This speaker impedance calculator finds the total load of speakers wired in series, parallel or series-parallel. List each speaker's impedance in ohms, pick the wiring and enter your amplifier's minimum rating, and it shows the total with the working, whether the load is safe for the amp and how the power is shared between the speakers.

Amplifiers are designed for a minimum load, usually 4 or 8 Ω. Wiring several speakers to one channel changes the load the amp sees: in series the ohms add up, in parallel they fall. Too low a load makes the amplifier deliver more current than it was built for, which can trip its protection, distort or burn out the output stage.

How the speaker impedance calculator works

The formula for series wiring is Z = Z1 + Z2 + …, and for parallel wiring 1 ÷ Z = 1 ÷ Z1 + 1 ÷ Z2 + …. Series-parallel splits the speakers into strings of equal size, adds the impedances within each string, then combines the strings in parallel. Power divides in proportion to impedance in series and in inverse proportion in parallel, so mixed impedances never share power equally.

First example. Two 8 Ω speakers in parallel give 1 ÷ (1/8 + 1/8) = 4 Ω, safe on a 4 Ω amp, with each taking half the power.

Second example. Four 8 Ω speakers as two series pairs give (8 + 8) ∥ (8 + 8) = 8 Ω, the same load as a single speaker.

How many 8 Ω speakers can go in parallel on a 4 Ω amp? Two; three would drop to 2.67 Ω.

Total impedance of identical speakers wired in series, parallel and series-parallel pairs

Speakers Each Series Parallel Series-parallel (strings of 2)
2 2 Ω 4 Ω 1 Ω Not applicable
3 2 Ω 6 Ω 0.667 Ω Not applicable
4 2 Ω 8 Ω 0.5 Ω 2 Ω
6 2 Ω 12 Ω 0.333 Ω 1.333 Ω
8 2 Ω 16 Ω 0.25 Ω 1 Ω
2 4 Ω 8 Ω 2 Ω Not applicable
3 4 Ω 12 Ω 1.333 Ω Not applicable
4 4 Ω 16 Ω 1 Ω 4 Ω
6 4 Ω 24 Ω 0.667 Ω 2.667 Ω
8 4 Ω 32 Ω 0.5 Ω 2 Ω
2 6 Ω 12 Ω 3 Ω Not applicable
3 6 Ω 18 Ω 2 Ω Not applicable
4 6 Ω 24 Ω 1.5 Ω 6 Ω
6 6 Ω 36 Ω 1 Ω 4 Ω
8 6 Ω 48 Ω 0.75 Ω 3 Ω
1 8 Ω 8 Ω 8 Ω Not applicable
2 8 Ω 16 Ω 4 Ω Not applicable
3 8 Ω 24 Ω 2.667 Ω Not applicable
4 8 Ω 32 Ω 2 Ω 8 Ω
6 8 Ω 48 Ω 1.333 Ω 5.333 Ω
8 8 Ω 64 Ω 1 Ω 4 Ω
2 16 Ω 32 Ω 8 Ω Not applicable
3 16 Ω 48 Ω 5.333 Ω Not applicable
4 16 Ω 64 Ω 4 Ω 16 Ω
6 16 Ω 96 Ω 2.667 Ω 10.67 Ω
8 16 Ω 128 Ω 2 Ω 8 Ω

Tips and pitfalls

FAQ

How do you calculate speaker impedance in parallel?

Add the reciprocals of each impedance and take the reciprocal of the total. Two 8 Ω speakers give 1 ÷ (1/8 + 1/8) = 4 Ω, and four give 2 Ω. For identical speakers you can just divide one speaker's impedance by how many there are.

How do you calculate speaker impedance in series?

Add the impedances together. Two 8 Ω speakers in series make 16 Ω and two 4 Ω speakers make 8 Ω. Series wiring raises the load, which is safe for the amplifier but lowers the power it can deliver, since a higher impedance draws less current at the same voltage.

What happens if the speaker impedance is too low?

The amplifier tries to push more current than it was designed for. It may run hot, distort, shut down under its protection circuit or, in older or cheaper designs, fail. Always keep the total at or above the amplifier's rated minimum, and give it a little margin for loud use.

Can I wire 4 speakers to a 2-channel amp?

Yes. Two 8 Ω speakers in parallel on each channel give 4 Ω per channel, which suits most home and car amplifiers rated for 4 Ω. If the amp is only rated for 8 Ω, wire each pair in series instead for 16 Ω, accepting lower volume.

Is it better to wire speakers in series or parallel?

Parallel is more common because the amplifier delivers more power into a lower load and one failed speaker does not silence the rest. Series is safer for the amplifier but quieter. Series-parallel combines both, keeping the load at the speakers' own rating while driving four or more of them.

See also: all Electronics tools, Physics, Chemistry.

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