Speaker Impedance Calculator: Series, Parallel and Subwoofer Wiring
Enter your speakers and your amplifier's minimum stable impedance. The calculator shows the total load for every way to wire them, flags the ones that are too low for your amp, and shows how the power is shared.
Found on the spec sheet, e.g. “2 Ω stable”. Bridged mode usually doubles it.
Adds an ideal estimate of the power into each load.
The load that rating was measured at.
Identical speakers
Whole number, 1 to 64.
| Wiring | Total load | Your amp |
|---|---|---|
| All in series | 32 Ω | Safe |
| 2 parallel strings of 2 in series | 8 Ω | Safe |
| All in parallel | 2 Ω | Too low for your amp |
Series-parallel layouts use equal strings, so every speaker shares power equally. A layout is only listed if it divides evenly.
Check before you connect
Series and parallel speaker wiring formulas
Two rules cover almost every speaker wiring question.
Impedance, measured in ohms (Ω), is how much a speaker load resists the current an amplifier sends it. A lower impedance draws more current and works the amplifier harder, which is why the load matters more than almost any other wiring detail.
Series: impedances add
Total = Z1 + Z2 + Z3 … Two 8 Ω speakers in series present 16 Ω. The amplifier has an easier job, but it delivers less power, and one failed speaker breaks the whole chain.
Parallel: reciprocals add
1 ÷ Total = 1 ÷ Z1 + 1 ÷ Z2 + … For identical speakers this simplifies to Total = Z ÷ N. Two 8 Ω speakers in parallel present 4 Ω, and three present 2.67 Ω. Parallel is where damage happens, because it is easy to add speakers without noticing the load has dropped below what the amplifier can drive.
Common combinations
| Speakers | In series | In parallel |
|---|---|---|
| Two 8 Ω speakers | 16 Ω | 4 Ω |
| Three 8 Ω speakers | 24 Ω | 2.67 Ω |
| Four 8 Ω speakers | 32 Ω | 2 Ω |
| Two 4 Ω speakers | 8 Ω | 2 Ω |
| Four 4 Ω speakers | 16 Ω | 1 Ω |
| Two 16 Ω speakers | 32 Ω | 8 Ω |
How series-parallel wiring works
Drive more speakers without lowering the load.
Series-parallel wiring joins speakers in equal series strings, then puts the strings in parallel. A string of s speakers has impedance s × Z, and p equal strings in parallel divide that by p.
With four 8 Ω speakers you have three choices, and the middle one is the useful one: two pairs in series (16 Ω each) wired in parallel give 8 Ω, so the amplifier sees the same load as it would from a single speaker.
| Wiring of four 8 Ω speakers | Total load |
|---|---|
| All in series | 32 Ω |
| 2 parallel strings of 2 in series | 8 Ω |
| All in parallel | 2 Ω |
The calculator lists every valid layout for any number of identical speakers. A layout appears only if the speakers divide into equal strings, because unequal strings would share power unevenly.
Subwoofer wiring: single and dual voice coil
Dual voice coil subs give you a choice. Here is every result.
A single voice coil (SVC) subwoofer has one coil and one pair of terminals, so its impedance is fixed. A dual voice coil (DVC) subwoofer has two coils. Those coils are building blocks, not the final impedance: a "dual 4 Ω" sub presents 8 Ω with its coils in series or 2 Ω with its coils in parallel.
With more than one sub you make two decisions: how to wire each sub's coils, then how to wire the subs together.
| Subwoofers | Wiring | Final load |
|---|---|---|
| One single 4 Ω | no choice | 4 Ω |
| One dual 4 Ω | coils in series | 8 Ω |
| One dual 4 Ω | coils in parallel | 2 Ω |
| One dual 2 Ω | coils in series | 4 Ω |
| One dual 2 Ω | coils in parallel | 1 Ω |
| Two single 4 Ω | subs in series | 8 Ω |
| Two single 4 Ω | subs in parallel | 2 Ω |
| Two dual 4 Ω | coils in series, subs in series | 16 Ω |
| Two dual 4 Ω | coils in series, subs in parallel | 4 Ω |
| Two dual 4 Ω | coils in parallel, subs in series | 4 Ω |
| Two dual 4 Ω | coils in parallel, subs in parallel | 1 Ω |
| Two dual 2 Ω | coils in series, subs in series | 8 Ω |
| Two dual 2 Ω | coils in series, subs in parallel | 2 Ω |
| Two dual 2 Ω | coils in parallel, subs in series | 2 Ω |
| Two dual 2 Ω | coils in parallel, subs in parallel | 0.5 Ω |
The answer many people search for: two dual 4 Ω subs reach 1 Ω by wiring each sub's coils in parallel (2 Ω each) and then wiring the two subs in parallel. That is only safe if the amplifier is stable at that load.
Matching the load to your amplifier
The one rule: never go below the amplifier's minimum stable impedance.
Find the lowest impedance your amplifier is rated to drive on its spec sheet, usually written "2 Ω stable" or "minimum load 4 Ω". Enter it at the top of the calculator and every result is checked against it.
Why lower impedance is harder work
At the same voltage, current is voltage divided by impedance, so a 4 Ω load draws twice the current of an 8 Ω load. An amplifier that delivers more watts into 4 Ω is doing so by supplying more current, with more heat and more stress on the output stage. Driving a load below the rated minimum can trigger protection or destroy the amplifier.
Bridged amplifiers
Bridging combines two channels into one with roughly double the power, but each channel sees half the effective load. An amplifier stable to 4 Ω per channel usually needs an 8 Ω minimum when bridged. Enter the bridged minimum from the manual, not the per-channel figure.
Unequal speakers share power unequally
In parallel, the lower-impedance speaker takes more power. A 4 Ω and an 8 Ω speaker in parallel split the amplifier's power 66.7% to 33.3%, so the 4 Ω speaker is driven twice as hard. In series it reverses: the higher-impedance speaker gets the larger share.
Nominal impedance is an average
"8 Ω" is a nominal figure. A real speaker's impedance changes with frequency and can dip well below its rating, so leave a margin when a result lands right on your amplifier's limit.
Speaker Impedance Calculator FAQ
+ What is the impedance of two 8 ohm speakers in parallel?
4 Ω. For identical speakers wired in parallel the total is the impedance of one divided by the number of speakers. In series, two 8 Ω speakers give 16 Ω.
+ Is it better to wire speakers in series or parallel?
Neither is better in general. Parallel gives a lower load, so the amplifier can deliver more power, but only if it is rated for that load. Series gives a higher load that is easier on the amplifier but delivers less power. The deciding rule is to stay at or above your amplifier's minimum stable impedance.
+ What happens if the speaker impedance is too low for the amplifier?
The amplifier has to supply more current than it was designed for. At best it overheats and shuts down through its protection circuit. At worst the output stage fails. Always check the total load against the amplifier's minimum rating before connecting.
+ Can I mix 4 ohm and 8 ohm speakers?
It works electrically, but the power is split unequally. In parallel a 4 Ω and an 8 Ω speaker share 66.7% and 33.3% of the power, so the 4 Ω speaker gets twice as much. Matching speakers is safer.
+ How do I wire two dual 4 ohm subwoofers to 1 ohm?
Wire each subwoofer's two coils in parallel, which gives 2 Ω per sub, then wire the two subs in parallel for 1 Ω. Only do this if your amplifier is stable at 1 Ω.
Related guides
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