How to wire speakers in series and parallel

Why the wiring changes the load

Impedance, measured in ohms (Ω), is the load your amplifier sees. When you connect more than one speaker, or more than one voice coil, to the same amp output, the way you wire them changes that load. Kicker’s tech paper on speaker wiring notes that the math is the same as for resistors, and that you must observe polarity in both series and parallel wiring. One caution before the math: an “8 ohm” speaker is not 8 ohms at every frequency. The rating is a nominal number, and the real load rises and dips (speaker impedance curves, explained). The figures below use nominal ratings.

Series: impedances add

How to wire it (Kicker): amp positive to the first speaker’s positive. First speaker’s negative to the second speaker’s positive. Second speaker’s negative back to the amp’s negative. For more speakers, keep chaining negative to the next positive. The math: add the impedances.

Kicker says the coils do not have to match, but mismatched coils change how much power each speaker gets.

Parallel: impedance divides

How to wire it (Kicker): all the positive leads to the amp’s positive terminal, all the negative leads to the amp’s negative terminal. The math, equal speakers: divide one speaker’s impedance by the number of speakers. Kicker says this shortcut only works when every coil has the same impedance.

Mixed speakers: Kicker gives the general formula 1/Rtotal = 1/R1 + 1/R2 + 1/R3. Its example, two 4 Ω speakers and one 8 Ω speaker, works out to 0.25 + 0.25 + 0.125 = 0.625, so Rtotal = 1.6 Ω. Kicker warns that the formula gives the right load, but the speakers will not get equal power.

Series-parallel: four drivers, one driver’s rating

With four identical speakers, wire two pairs in series, then wire the two pairs in parallel. Kicker’s example with four 4 Ω speakers: each series pair is 4 + 4 = 8 Ω, and 8 Ω // 8 Ω = 4 Ω (the “//” means “in parallel with”). The total equals one speaker’s rating. Kicker notes you need at least four single-coil speakers for this. A pair of dual voice coil drivers works out the same way. With identical speakers, the power splits evenly. Amplified Parts’ four-speaker example gives each speaker one fourth of the amp’s output. Mixing values breaks that balance. Kicker’s example: put two 4 Ω speakers in series (8 Ω) and wire that pair in parallel with one 8 Ω speaker. The amp sees 4 Ω, but the 8 Ω speaker gets double the power of each 4 Ω speaker, and Kicker says there is no way to balance power across all three on the same amp output. Use identical drivers when you wire them together.

Check the result against your amp

Compare the total with your amplifier’s stated minimum load. The real impedance can dip below the nominal figure, and a lower impedance draws more current from the amp. Check the minimum, not just the label (matching amp power to DIY speakers). If you are choosing an amp module, see class-D modules that do not fight your layout. Two identical woofers in one cabinet is the common DIY case. Kicker’s math gives 4 Ω for two 8 Ω drivers in parallel, and 16 Ω for the same pair in series. If a crossover feeds them, design it for the combined load (how to choose a crossover frequency).

Before you power up

• Every wire marked + and −, and polarity matched at each speaker (How to check speaker polarity)
• Total impedance worked out from the nominal ratings
• Total checked against the amp’s minimum load, with dips in mind
• Only identical drivers wired together
• Impedance measured after the build if you can (REW basics)

What gauge speaker wire? See what gauge speaker wire for DIY speakers?.