Speaker Impedance Wiring Calculator (Series, Parallel & Amp Load)

How it works

series: Z = Z₁ + Z₂ + … · parallel (equal): Z = Z₁ ÷ n; unequal: 1/Z = 1/Z₁ + 1/Z₂ + … · series-parallel (pairs): Z = 2 Z₁ ÷ (n/2) · equal speakers share amplifier power equally · never load an amplifier below its minimum rated impedance

Every speaker connected to an amplifier changes the load it sees: wiring in series adds impedances, wiring in parallel divides them, and the combination decides both whether the amplifier is safe and how much power it can deliver, since solid-state amps push more current — and more watts — into lower impedances until they hit their limit. Below the rated minimum the output stage overheats or shuts down, so multi-speaker rigs are arranged in series-parallel groups that land back near a comfortable four or eight ohms. When the speakers match each other, the power divides equally among them whichever way they are wired, which makes the per-speaker figure easy to check against their ratings.

Worked example

Four 8 Ω speakers on an amp rated 300 W at 8 Ω and 500 W at 4 Ω: wired series-parallel they present 8 Ω — safe for a 4 Ω-minimum amp — and take about 300 W, 75 W each, comfortably under a 150 W rating. All in parallel they would be 2 Ω, below the amp's minimum; all in series 32 Ω, safe but only about 75 W in total.

Frequently asked questions