Speaker Impedance
Combine speakers in series, parallel or series-parallel and I compute the total impedance, the power each one receives and whether the load is safe for your amplifier (minimum stable).
Impedance by count
| Speakers | Z total | vs minimum |
|---|
your current configuration · in parallel the impedance drops as you add speakers.
How it is computed · series, parallel and safety
1. Series: impedances add up.
Z = Z₁ + Z₂ + … + Zₙ. With n equal speakers of
Z → Z·n. Example: 2×8 Ω = 16 Ω.
2. Parallel: reciprocals add up.
1/Z = 1/Z₁ + … + 1/Zₙ. With n equal → Z/n.
Example: 4×8 Ω = 2 Ω.
3. Series-parallel: you build
G groups in parallel, each with N speakers in series.
Zgroup = N·Z and Ztotal = Zgroup / G. Example:
4×8 Ω in 2 groups of 2 in series = (2·8)/2 = 8 Ω.
4. Power: the amp delivers
P into the total impedance. The voltage across the load is
V = √(P·Z). With equal speakers the power splits evenly:
each one gets P / n.
5. Safety: if the total impedance
falls below the amplifier's minimum stable load, current rises and the
amp can overheat, go into protection or fail. Always keep the load
≥ the manufacturer's minimum.
Resistive model (nominal impedance, equal speakers). Real impedance varies with frequency; use the nominal value as a design reference.
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How it works
The calculator combines identical speakers in three topologies and returns the total impedance: in series impedances add up (n × Z), in parallel the inverses add and with equal speakers it becomes Z / n, and in series-parallel groups of N speakers in series are connected in parallel: Ztotal = (N × Z) / G. It also splits the amplifier power among the speakers (with equal units each receives P / n) and computes the voltage and current across the load.
The key output is the safety verdict: it compares the total impedance against the amplifier minimum stable load (4 Ω on typical home gear, 2 Ω on robust or class-D amplifiers). If the load falls below it, the amplifier draws more current than it tolerates and can overheat, go into protection or fail; the tool flags it in red and suggests switching to series or series-parallel. The model is resistive using nominal impedance: real impedance varies with frequency, but the nominal value is the correct design reference.
Example: 4 speakers of 8 Ω on an amplifier with a 4 Ω minimum
- In parallel:
8 / 4 = 2 Ω, below the 4 Ω minimum: dangerous load. - In series-parallel (2 groups of 2 in series):
Zgroup = 2 × 8 = 16 ΩandZtotal = 16 / 2 = 8 Ω: safe load. - With a 200 W amplifier, each speaker receives
200 / 4 = 50 Win both configurations.