Why the total impedance matters
An amplifier is designed to drive a minimum load, often 4 Ω or 8 Ω. Connect speakers whose combined impedance is lower than that, and the amplifier tries to push more current than it was built for: it runs hot, distorts, or goes into protection. Wiring several speakers to one channel therefore starts with one question: what impedance does the amplifier see?
The formulas for identical speakers
- In series (one after the other), impedances add: two 8 Ω speakers give 16 Ω.
- In parallel (all on the same terminals), the impedance is divided by the number of speakers: two 8 Ω speakers give 4 Ω.
- Series-parallel: you build chains of speakers in series, then connect the chains in parallel. Total = impedance × speakers per chain ÷ number of chains.
Four 8 Ω speakers wired as two chains of two give 8 × 2 ÷ 2 = 8 Ω, a safe load for almost any amplifier. Four in parallel would give only 2 Ω.
| Speakers (8 Ω each) | Wiring | Total impedance |
|---|---|---|
| 2 | Series | 16 Ω |
| 2 | Parallel | 4 Ω |
| 4 | 2 × 2 series-parallel | 8 Ω |
| 4 | Parallel | 2 Ω |
| 3 | Series | 24 Ω |
How the power is shared
With identical speakers, each one receives the same share of the amplifier’s output. The calculator estimates the power per speaker, the amplifier’s output voltage at its rated power (V = √(P × R)) and the current it delivers into your load. A higher total impedance draws less power from a solid-state amplifier: at 16 Ω, a 100 W at 8 Ω amplifier delivers roughly half its rated power.
Practical tips
- Mix only identical speakers: different impedances or sensitivities share power unevenly.
- Respect polarity on every speaker, or the cones will move in opposite directions and cancel the bass.
- Long cable runs add resistance; use thicker wire for low-impedance loads.
- For background music with many speakers, commercial installers use 70 V or 100 V line systems with transformers instead of impedance matching.