Series vs Parallel Speakers and How Each Changes Impedance

Choose around the amplifier’s capabilities

If you’re putting two passive speakers on one amplifier channel, we’d check the amp’s specifications before choosing the wiring, because the lower load from parallel wiring puts greater demand on the amplifier. That gives you a useful decision point before you connect any terminals.

These calculations concern passive speakers, which need a separate power amplifier, and speaker voice coils. Active or powered speakers contain their own amplifiers, so linking their signal inputs is a different connection task.

• connecting speakers to a TV

Calculate the load for one channel

Use the speakers’ specified impedance for your calculation. An ohmmeter reads static resistance, while speaker impedance changes with frequency, so a resistance reading isn’t the number to substitute for the speaker’s impedance specification.

For series wiring, add the impedances of every speaker in the chain. For parallel wiring with equal-impedance speakers, divide one speaker’s impedance by the number connected to that channel. The parallel shortcut applies only when all those impedances are equal.

The same arithmetic extends beyond two speakers. Three 8-ohm speakers in series total 24 ohms; three in parallel total about 2.67 ohms. Adding that third parallel speaker lowers the load again, so speaker count belongs in the calculation every time you expand the setup.

With two 4-ohm voice coils, series gives 8 ohms and parallel gives 2 ohms. Four equal 4-ohm coils in parallel give 1 ohm, while four equal 8-ohm coils give 2 ohms. These are calculated loads to compare with your amplifier’s capabilities.

Match both impedance and power

Match the amplifier to the speaker specifications, including impedance and power rating. A speaker’s power rating describes how many watts it can accept, while amplifier output changes with the connected load. Read those specifications together when deciding whether a connection suits your gear.

For a Yamaha P3500S, two 8-ohm speakers connected in parallel make a supported 4-ohm load. In its stereo output example, the P3500S delivers 350W + 350W with 8-ohm loads and 450W + 450W with 4-ohm loads. That illustrates why changing impedance also changes the power question.

Keep those model names separate when checking your equipment: the supported 4-ohm example is P3500S, and the 2-ohm prohibition names P3500. Use the specifications for the exact amplifier you have to choose its load.

For a QSC cinema system, the DCA 1222 provides a different, model-specific example: it can drive up to five 8-ohm speakers per channel in parallel, totaling 1.6 ohms. If you’re unsure whether your QSC configuration is suitable, contact QSC Application Engineers before ordering or installing the amplifiers and speakers.

• 4-ohm and 8-ohm speakers

What changes in the sound

QSC recommends parallel wiring when multiple cinema surround speakers share an amplifier channel, citing sound quality, reliability and dynamic headroom. That recommendation concerns cinema surrounds with suitable amplification; your connection still has to fit your amplifier’s supported load.

The electrical distinction is voltage sharing. In QSC’s cinema comparison, parallel speakers receive the same applied voltage. Series speakers divide the voltage, and the split is equal only when the two loads are perfectly equal.

Speaker impedance varies with frequency, and two speakers’ impedance curves can differ. In a series connection, those differences change how the speakers share voltage across the frequency range, affecting their frequency response. Matching the printed ohm ratings gives you the load calculation, while the changing impedance curves explain the performance tradeoff.

QSC’s series example also shows reduced amplifier control over cone motion, described as damping. Each speaker has the other speaker’s impedance between it and the amplifier’s output: an illustrative damping factor of 250 falls to slightly below 1, with cable resistance reducing it further.

For an output decision, look at the amplifier’s power specification at the proposed load and the speakers’ power ratings. The P3500S example shows increased amplifier output at the lower supported impedance; QSC’s comparison explains why sharing voltage in series can affect what reaches each speaker.

What happens if one speaker goes open circuit

An open circuit interrupts the shared current path through series speakers. If a speaker or its protection fuse opens that path, the whole series chain stops playing.

In QSC’s parallel comparison, the remaining speakers keep operating at their previous level when one speaker’s path opens. This is specifically an open-circuit comparison, so use it to understand that failure pattern rather than every possible speaker fault.

Keep mixed impedances out of these connections

Keep the speakers or coils at equal impedance for the calculations and connections below. Kicker advises against mixing speaker impedances on the same amplifier terminals in car audio, because different impedances affect how much power each speaker receives.

That power distribution matters even when a mixed parallel load totals an impedance the amplifier can handle. The speakers receive unequal power, so a suitable total load alone does not establish a suitable mixed-speaker arrangement.

If you’re working with individual voice coils, use each coil’s impedance and count each coil in the calculation. Kicker’s speaker and voice-coil wiring reference (opens in a new tab) is useful alongside the terminal connections.

Connect a series chain

Once the calculated series load matches your amplifier’s specifications, follow the terminal markings carefully. The link between speakers goes from negative to positive; that link is part of the series path, so keep its polarity distinct from the connections at the amplifier.

1. Connect the amplifier channel’s positive terminal to the first speaker’s positive terminal. The first connection is positive to positive.
2. Connect the first speaker’s negative terminal to the second speaker’s positive terminal. For additional speakers, continue negative to the next positive, leaving the last speaker’s negative terminal for the return.
3. Connect the last speaker’s negative terminal to the same amplifier channel’s negative terminal. You now have one path through the speakers and back to that channel.

You can identify an existing series connection by tracing that terminal-to-terminal path: it passes through one speaker before reaching the next. The intermediate negative-to-positive links distinguish it from a parallel connection.

Connect parallel speakers and check the pattern

Before adding a parallel speaker, recalculate the total impedance and compare it with the amplifier’s supported load. Each added equal-impedance speaker lowers the total, which is why the original connection’s suitability has to be checked again when you expand it.

Connect every speaker’s positive terminal to the amplifier channel’s positive terminal, and every speaker’s negative terminal to that channel’s negative terminal. Keep polarity consistent throughout: all positives share one connection, and all negatives share the other.

Cable routing can look different from the electrical connection. On a Yamaha CBR12, a dedicated speaker cable carries the amplifier output into one input connector, and another dedicated speaker cable carries it from the other connector to the second speaker. That arrangement is parallel even though the cables run from one cabinet to the next.

When identifying your finished wiring, follow the terminal connections rather than the physical line of cabinets. In parallel, every speaker connects across the same amplifier positive and negative terminals; in series, the path continues through negative-to-positive links between speakers.