Speaker Impedance Calculator
Series and Parallel Wiring Don't Combine the Same Way
Wiring two speakers to one amplifier channel changes the total impedance the amplifier sees, and the direction of that change depends entirely on whether the speakers are wired in series or parallel. Series wiring always raises total impedance; parallel wiring always lowers it. Getting this wrong risks either an underpowered pair of speakers or an amplifier load low enough to trigger thermal protection or damage.
The Formulas
Series Wiring: Z_total = Z1 + Z2
Parallel Wiring: Z_total = (Z1 × Z2) / (Z1 + Z2)
Parallel Wiring: Z_total = (Z1 × Z2) / (Z1 + Z2)
Common Speaker Pairings
| Z1 | Z2 | Series total | Parallel total |
|---|---|---|---|
| 8 Ω | 8 Ω | 16 Ω | 4 Ω |
| 4 Ω | 8 Ω | 12 Ω | 2.667 Ω |
| 4 Ω | 4 Ω | 8 Ω | 2 Ω |
Two identical speakers in parallel always halve the impedance of a single speaker; two identical speakers in series always double it.
Where This Gets Used
- Multi-speaker amp channels — car audio and PA setups routinely run two or more speakers off one amplifier channel, and the wiring scheme decides whether the amp sees 2, 4, 8, or 16 ohms.
- Matching an amplifier's minimum load — most amplifiers specify a minimum stable impedance (commonly 4 ohms); wiring speakers in parallel below that threshold risks overheating or shutdown.
- Distributed audio and 70V systems aside — for standard low-impedance runs, series/parallel math is the first check before adding a third or fourth speaker.
How to Use This Calculator
- Select the wiring configuration: Series or Parallel.
- Enter Speaker 1 Impedance in ohms.
- Enter Speaker 2 Impedance in ohms.
- Select Calculate to see the total impedance the amplifier will see.
Related Calculations
Once total impedance is known, size the cable run with the Speaker Wire Gauge Calculator, or check output level changes with the Decibel Calculator.