Speaker impedance calculator
How many cabinets can you hang on one amp channel? Enter the wiring and check the load before you power up.
How it works
Parallel: 1/Z = 1/Z₁ + 1/Z₂ + …
Identical speakers: Z = Zeach × (in series) ÷ (strings in parallel)
Two 8 Ω cabinets in parallel make 4 Ω. Four 8 Ω cabinets as two series pairs, with the pairs in parallel, make 8 Ω again: twice the speakers at the same load.
With identical speakers the amp's power splits evenly, so each speaker gets the amp's output divided by the number of speakers. Mixing impedances doesn't split evenly. In parallel, the lower-impedance speaker takes more of the power.
Common combinations
| Wiring | 8 Ω cabinets | 4 Ω cabinets |
|---|---|---|
| 1 cabinet | 8 Ω | 4 Ω |
| 2 in parallel | 4 Ω | 2 Ω |
| 3 in parallel | 2.67 Ω | 1.33 Ω |
| 4 in parallel | 2 Ω | 1 Ω |
| 2 in series | 16 Ω | 8 Ω |
| 4 as 2 series pairs in parallel | 8 Ω | 4 Ω |
Field notes
- Nominal isn't the minimum. An "8 Ω" speaker's real impedance swings with frequency and often dips below its rating near the low end. A 4 Ω load on paper can look closer to 3 Ω to the amp, which is why the amp's minimum load is a floor, not a target.
- Daisy-chained cabinets are in parallel. A speakON or 1/4" link-through jack on the back of a cabinet wires the next box in parallel. Two linked 8 Ω boxes on one channel is 4 Ω.
- Bridged mode doubles the load the amp sees per side. Many amps that are fine at 4 Ω per channel want 8 Ω minimum when bridged. Check the bridged rating separately.
- Series wiring has a catch. If one speaker in a series string opens up, the whole string goes silent.
- 70V systems work differently. Transformer-tapped speakers are sized by watts, not ohms. Use the 70V line calculator for those.
FAQ
What happens if the load is below the amp's minimum?
The amp has to deliver more current than it was designed for. It may run hot, go into protection, or distort, and in the worst case it can fail.
Is running a higher impedance than the minimum safe?
Yes. The amp just delivers less power. An amp rated 500 W at 4 Ω typically makes somewhere around 300 W at 8 Ω.