How Do You Wire Speakers in Series?
Series wiring adds impedances and lowers volume. Here is the wiring order, the arithmetic for two and four speakers, and when parallel is the better choice.
To wire speakers in series, run the amplifier’s positive to the first speaker’s positive, link the first speaker’s negative to the second speaker’s positive, then return the second speaker’s negative to the amplifier. Impedances add, so two 8 ohm speakers become a 16 ohm load. Series wiring raises impedance and lowers volume, which is the opposite of what most people want.
Series and parallel get mixed up constantly, and the consequence is not academic. Wire two speakers the wrong way onto one channel and you can hand your amplifier a 2 ohm load it was never built to drive. The wiring itself takes two minutes. Knowing which one you need is the part worth reading.
How to wire two speakers in series
- Run a cable from the amplifier’s positive terminal to the positive terminal of speaker one.
- Run a cable from the negative terminal of speaker one to the positive terminal of speaker two. Nothing from this link goes back to the amplifier.
- Run a cable from the negative terminal of speaker two back to the amplifier’s negative terminal.
The current now flows through both speakers one after the other, like two batteries end to end. Add a third speaker by continuing the chain: negative of two to positive of three, and negative of three back to the amplifier.
Keep polarity consistent all the way round. A single speaker connected backwards in the chain will play out of phase, and the two will cancel each other through the bass and lower midrange.
The arithmetic
In series, impedances add:
| Speakers | Series total | Parallel total |
|---|---|---|
| Two 8 ohm | 16 ohms | 4 ohms |
| Two 4 ohm | 8 ohms | 2 ohms |
| Three 8 ohm | 24 ohms | 2.7 ohms |
| Four 8 ohm | 32 ohms | 2 ohms |
| Two 8 ohm plus two 8 ohm, series pairs in parallel | 8 ohms total | |
That last row is the useful trick. Wire each pair in series to make 16 ohms, then connect the two 16 ohm pairs in parallel to come back to 8 ohms. Four speakers on one channel, and the amplifier sees the load it expects.
For parallel, the formula for identical speakers is the impedance divided by the number of speakers. For different values it is one divided by the sum of the reciprocals, which is a good reason to use matching speakers.
What series wiring does to the sound
Two things, and both are worth knowing before you commit.
Volume drops. Doubling the impedance roughly halves the power the amplifier delivers, and that power is then split between two speakers. Expect each speaker to be noticeably quieter than it would be alone.
Bass control loosens. An amplifier’s damping factor is its output impedance compared with the load, and putting a second speaker’s voice coil in the current path degrades that. The practical result is bass that sounds softer and less defined. On small speakers you may not care. On anything with a real woofer, you will hear it.
There is also a subtler issue: each speaker’s impedance curve now affects the other, since they share the same current. Two identical speakers behave predictably. Two different models interact in ways nobody designed for.
When to use series and when to use parallel
Use series when you need to raise impedance to protect an amplifier. The classic case is two 4 ohm speakers on an amplifier rated 8 ohms only: wired in series they present 8 ohms and everything is safe.
Use parallel when you need volume and the amplifier can handle the lower load. Two 8 ohm speakers in parallel give 4 ohms, which any receiver rated 4 to 16 ohms will drive happily, and each speaker plays at close to full output.
Use series parallel when you have four speakers and one channel, as in the table above.
Whichever you choose, check the amplifier’s rating first. Our explainer on what ohm means for speakers covers why too low is what damages equipment and too high is merely quiet.
The safer option for multiple rooms
If you are running speakers in several rooms from one amplifier, do not do the arithmetic and hope. An impedance matching speaker selector switch handles the load calculation internally, gives you per room volume control, and costs USD 60 to 150.
For anything beyond four pairs, the commercial answer is a 70 volt distributed system, where each speaker has a small transformer and taps a set number of watts. That is how offices and restaurants run twenty ceiling speakers off one amplifier, and it sidesteps impedance entirely.
Frequently asked questions
Does wiring speakers in series reduce the sound quality?
It reduces volume and softens bass control, which many people hear as a loss of quality. The impedance rise means the amplifier delivers less power, and having a second voice coil in the current path lowers the damping factor so the amplifier grips the woofer less tightly. With two identical, efficient speakers in a small room, the effect is minor. With mismatched or demanding speakers, it is obvious.
Is it better to wire speakers in series or parallel?
Parallel is better for volume, series is better for protecting an amplifier that cannot handle a low impedance. Two 8 ohm speakers in parallel present 4 ohms and play loud, which suits any modern receiver. Two 4 ohm speakers in series present 8 ohms and keep an older amplifier safe. Check what your amplifier is rated for and let that decide.
Can I wire two speakers to one channel?
Yes, in either series or parallel, as long as the resulting impedance is within your amplifier’s rating. Two 8 ohm speakers in parallel give 4 ohms, which most modern receivers handle. Two 4 ohm speakers in parallel give 2 ohms, which almost nothing outside professional equipment will tolerate, so wire those in series instead.
How do I calculate speaker impedance in series?
Add the individual impedances together. Two 8 ohm speakers in series present 16 ohms, three present 24 ohms, and an 8 ohm plus a 4 ohm speaker presents 12 ohms. Parallel works the other way: for identical speakers, divide the impedance by how many you have connected, so two 8 ohm speakers in parallel present 4 ohms.