Speaker Impedance Calculator
The load an amplifier sees from several drivers wired in series, in parallel or series-parallel, with the current and voltage.
Results
Impedance the amplifier sees
8.0000
Ω
Power each driver gets
50.000
W
Current the amplifier must supply
5.0000
A
Voltage across the load
40.0000
V
Branches
2
Drivers in each branch
2.00
Load for the amplifier
4 Ω or more — most amplifiers are happy
Does the wiring work?
Yes
What this tool does
Wiring speakers in parallel halves the impedance each time you double them, and an amplifier that is happy into 8 ohms can overheat into 2. Series-parallel exists to avoid exactly that: four 8-ohm drivers in two series pairs, paralleled, come back to 8 ohms. The page gives the load, the current the amplifier has to deliver, and a warning when the wiring needs an even number of drivers and you have an odd one.
Formula
series: Z = n Z₁ · parallel: Z = Z₁ ÷ n · series-parallel in two branches: Z = Z₁ n ÷ 4 · I = √(P ÷ Z)
Variables
| Symbol | Meaning | Unit |
|---|---|---|
z1 | Impedance of one driver | Ω |
n | How many drivers | — |
wi | How they are wired | — |
pw | Power the amplifier delivers | W |
ZT | Impedance the amplifier sees | Ω |
PD | Power each driver gets | W |
CU | Current the amplifier must supply | A |
VO | Voltage across the load | V |
BR | Branches | — |
PB | Drivers in each branch | — |
SF | Load for the amplifier | — |
EV | Does the wiring work? | — |
Worked example
- Impedance of one driver8 Ω
- How many drivers4
- How they are wired3
- Power the amplifier delivers200 W
- Impedance the amplifier sees8.0000 Ω
- Power each driver gets50.000 W
- Current the amplifier must supply5.0000 A
- Voltage across the load40.0000 V
- Branches2
- Drivers in each branch2.00
- Load for the amplifier4 Ω or more — most amplifiers are happy
- Does the wiring work?Yes
Limitations
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.
- Mixing units is the most common source of error. Convert every input to the units shown next to each field before calculating.