Speaker Impedance Calculator
Calculate total nominal speaker load impedance in Ohms (Ω) for series, parallel, and series-parallel audio speaker cabinet configurations.
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How Speaker Impedance is Calculated
Impedance (measured in Ohms, Ω) is the AC electrical resistance a loudspeaker voice coil presents to an audio amplifier:
Parallel Wiring (Divides)
1 / Z_total = (1 / Z1) + (1 / Z2) + ...
Two 8Ω speakers in parallel = 4 Ohms.
Series Wiring (Adds)
Z_total = Z1 + Z2 + ...
Two 8Ω speakers in series = 16 Ohms.
The Danger of Under-Impedance
Never connect a speaker load with lower impedance than your amplifier minimum rating (e.g. connecting a 2Ω load to an amplifier rated for 4Ω minimum). Lower impedance demands excessive current from output transistors, triggering thermal protection shutdown or burning out the power supply.
Frequently Asked Questions
What is series-parallel speaker wiring?
Series-parallel combines two pairs of speakers wired in series, then connects those two pairs together in parallel. For four identical speakers, the net impedance is exactly equal to the rating of a single speaker (e.g. four 8Ω speakers = 8Ω total).
Why do tube amps have 4, 8, and 16 Ohm selector switches?
Vacuum tube amplifiers use an output transformer to match high-impedance tubes to low-impedance voice coils. Mismatching taps can damage the output transformer windings through flyback voltage spikes.
Why does a multimeter read lower DC resistance than nominal impedance?
A multimeter measures static DC resistance (DCR), which is typically 15% to 25% lower than rated dynamic AC impedance (e.g. an 8-ohm speaker typically measures 6.0 to 6.8 ohms DC resistance).