Speaker Impedance Calculator
Enter the nominal impedance of each speaker (in ohms) to get the combined impedance in series or in parallel. The result is an estimate from nominal values and does not say whether an amplifier can drive it.
Formulas
- Series: combined impedance = Z₁ + Z₂ + … + Zₙ (the sum of the impedances).
- Parallel: combined impedance = 1 ÷ (1/Z₁ + 1/Z₂ + … + 1/Zₙ) (the reciprocal of the sum of the reciprocals). For two speakers this is Z₁ × Z₂ ÷ (Z₁ + Z₂).
A parallel combination is always lower than the lowest single impedance, and a series combination is at least as high as the highest. These are the same formulas as for resistors in series and in parallel. The calculation uses exact fractions, so there is no rounding error. A value that divides exactly is shown as an "exact value", and one that does not is shown as a "rounded value (7 significant digits)".
This is an estimate from nominal impedances
- Nominal impedance is the typical value the manufacturer gives for a speaker (8 Ω, 4 Ω and so on). The real impedance changes with frequency. This tool uses only the size of the nominal value; it does not handle changes with frequency or phase.
- It does not judge whether an amplifier can drive the combined impedance. Minimum load impedance, output power and protection differ between amplifiers, and the tool gives no rule-of-thumb figure either. Check the amplifier's specifications.
- Mixed series-and-parallel wiring is not handled. To connect two speakers in series and then wire that pair in parallel with another, first find the series result and then enter it as one row of the parallel calculation.
- The power or voltage each speaker receives is not calculated (speakers with different impedances share power differently when wired in parallel).
Examples
- 8 Ω + 8 Ω in series = 16 Ω.
- 8 Ω ‖ 8 Ω in parallel = 4 Ω.
- 4 Ω ‖ 8 Ω in parallel = 8/3 Ω (about 2.667 Ω, a rounded value).
- Three 8 Ω speakers in parallel = 8/3 Ω (about 2.667 Ω).
- 4 Ω + 8 Ω in series = 12 Ω.
Notes
- Enter each nominal impedance as a number greater than 0 (up to 9 digits before the decimal point and 6 decimal places). Use a period as the decimal separator; commas are accepted only as thousands separators.
- For voltage, current, power and resistance, see the Ohm's Law Calculator. For converting voltage and power ratios to decibels, see the Decibel Calculator.
Frequently asked questions
What is the impedance of two 8 Ω speakers in parallel?
4 Ω (1 ÷ (1/8 + 1/8)).
What if they are wired in series?
The impedances add. Two 8 Ω speakers in series give 16 Ω.
Can I tell whether my amplifier supports the combined impedance?
No. The tool does not judge this, because minimum load impedance differs between amplifiers. Check the amplifier's specifications.
Is the nominal impedance the same as the real impedance?
No. The nominal impedance is a typical value given by the manufacturer. The real impedance changes with frequency.