Music · Amps and speakers
Speaker impedance calculator.
List your speakers’ impedances, choose series or parallel and get the load your amplifier sees, plus how an amp’s power splits between unequal speakers.
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Combined load
Fill the form to see the result.
How do you calculate speaker impedance in series and parallel?
Speakers wired in series add: total = Z1 + Z2 + …. Speakers wired in parallel combine as the reciprocal of the sum of the reciprocals: total = 1 / (1/Z1 + 1/Z2 + …). Two identical speakers in parallel therefore halve the impedance, and two in series double it.
Worked example. Two 8 Ω speakers: in series 16 Ω, in parallel 4 Ω. Four 8 Ω speakers in parallel give 2 Ω. A 4 Ω and an 8 Ω speaker in parallel give 2.67 Ω, and with 100 W delivered into that load the 4 Ω speaker takes 66.7 W and the 8 Ω speaker 33.3 W.
Limits. Speaker impedance is a nominal figure that changes with frequency, and the results here treat each speaker as a plain resistance. The power split is a simplified model for the same reason. Always stay at or above the minimum load impedance your amplifier states, and mixed-impedance setups need extra care: run them only if the amp and speaker manuals allow it.
Frequently asked questions
What is the impedance of two 8 ohm speakers in parallel?
4 ohms. In series the same two speakers present 16 ohms.
What is the parallel impedance formula?
Total = 1 / (1/Z1 + 1/Z2 + ...). For two speakers it simplifies to Z1 x Z2 / (Z1 + Z2).
Does the louder speaker get more power in parallel?
The lower-impedance speaker draws more power in parallel, because the same voltage drives more current through it. In series the higher-impedance speaker gets more.
Can I wire a 4 ohm and an 8 ohm speaker together?
Electrically it is possible: 2.67 ohms in parallel. Whether it is safe depends on your amplifier’s minimum load, so check its manual first.
Is nominal impedance the same as resistance?
No. Nominal impedance is a rated value that varies across the frequency range, so these results are a guide to the load, not a measurement.
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Not professional advice
Electrical guide only, not professional advice. Wiring speakers to an amplifier outside its rated load can damage the equipment. Follow the amplifier and speaker manuals and use a qualified technician for installed or high-power systems.