Parallel vs. Series Impedance Loads

Power comes out of the amp from the positive terminal, connects to the speakers, then returns to the negative terminal. The ohm load is how much resistence the current encounters in the circuit. When shopping subwoofers, the “ohm” spec of the voice coils is very important.

The greater the impedance, the less voltage is reaching the voice coils. The less voltage that is reaching the voice coils, the lower the total output of the system is.

Series Circuits

In a series circuit, the current encounters one speaker after another in a series. The impedance load of each speaker is summed. With three single 4 ohm voice coil speakers wired in series, the impedance load is 4 + 4 + 4, or 12 ohms.

A basic series circuit where the amp positive is connected to the positive of the first speaker. The negative of that speaker connects to the positive of the next speaker, and so on until the last negative connects back to the amp’s negative terminal.

Parallel Circuits

In a parallel circuit, the current is connected to each positive terminal of the speakers, then travels back along the negative terminals. It’s a more complicated calculation than series. Luckily, for speakers of the same impedance, you can divide the impedance by the number of speakers.

So with two 4 ohm single voice coil speakers wired in parallel, the net load is 4 ohms ÷ 2 speakers or 2 ohms.

A basic parallel circuit where all positives are connected, and all negatives are connected. Notice the positive and negative flow in parallel to one another in the diagram.

Combining Series and Parallel Wiring

Things get a little more tricky when you have a circuit with both series and parallel wiring. Don’t worry! It’s just a matter of treating the series “branches” as a single speaker, then calculating the load of the parallel circuit.

Let’s say every speaker in this diagram has a single 4 ohm voice coil. First add the impedance for each series of 3 to get 12 ohms (4 + 4 + 4). If you think of each series group as a single speaker connected in parallel, that makes the parallel calculation 12 ohms ÷ 3 or 4 ohms.

In this example, if your amp puts out 900 W RMS with a 4 ohm load, the 900 W will be distributed among all the speakers.

Takeaway: The number of speakers, their impedance, and power handling determines your options for wiring to a certain impedance load.

Dual Voice Coil Subwoofers

Dual voice coils have double the winding length of single voice coils. That gives the speaker greater motor force and power handling. Most car audio subwoofers are dual voice coil.

Single voice coil subwoofers have 1 set of leads, which limits wiring options. Each of the two coils in a dual voice coil has its own leads.

With dual voice coil subwoofers, your wiring options open up. You can wire voice coils on the same sub in series or parallel. You can then wire the subs in series or parallel. This leaves you with 2 load options for most subwoofer configurations.

Notice the two sets of terminals at the top and bottom of the frame in this photo.These are the terminals for each separate voice coil.

Amplifier Stability

Now that you have a pretty good idea of how wiring works for dual voice coil subs, let’s add the amp into the mix.

You may have noticed the phrase “1 ohm stable” when reading about an amplifier. This tells you the lowest impedance load that is safe for the amplifier.

Before buying an amp, you will need to know your power needs at a specific load to get the best performance out of your system.

Subwoofer Wiring

How to Wire Dual Voice Coil Subwoofers in Series

1 Dual 2Ω Subwoofer wired to 4Ω

Wiring in series combines the coils to increase impedance. The flow of voltage in series connections is the sum of the impedance of each component, as they are connected in a single circuit.

Like old Christmas lights, when one component was removed, all of the lights down the line would turn off because the lights rely on the precedent light to pass voltage along the circuit.

Need to wire a dual voice coil subwoofer in series?

  • First, connect the positive lead from Voice Coil 1 to the positive speaker output from your amplifier.
  • Next, connect the negative lead from Voice Coil 1 to the positive lead on Voice Coil 2.
  • Finally, connect the negative lead from Voice Coil 2 to the negative output of the amplifier.

Need to wire more than 2 dual voice coil subwoofers in series?

2 Dual 1Ω Subwoofers wired to 4Ω

If you are wiring two or more dual voice coil subwoofers in a series, wire as described above, adding the next voice coil by connecting the negative lead of Voice Coil 1 to the positive lead of Voice Coil 3 and so on.

To determine the impedance after wiring voice coils in series, just add the impedance of the loads together.

How to Wire a Dual Voice Coil Subwoofer in Parallel

1 Dual 2Ω Subwoofer wired to 1Ω

Parallel wiring reduces impedance. When subwoofers are wired in parallel, they are connected to the amplifier in parallel paths and the voltage is split up so the same voltage is sent to each driver.

Need to wire a dual voice coil subwoofer in parallel?

  • Connect the positive voice coil leads together and wire them to the positive output terminal of your amplifier.
  • Next, connect the negative voice coil leads together and wire them to the negative output terminal of the amplifier.

Need to wire more than 2 dual voice coil subwoofers in parallel?

2 Dual 4Ω Subwoofers wired to 1Ω

Simply repeat the process described above, connecting the positive leads and negative leads.

To determine impedance after wiring voice coils in parallel, divide your subwoofer’s impedance by the number of subs you are using. For instance, if you have (2) 4Ω DVC subwoofers wired in parallel, 4Ω divided by 2 Subwoofers provides a 2Ω load.

Series and Parallel Wiring

2 Dual 2Ω Subwoofers, voice coils wired in Series, Speakers wired in Parallel to 2Ω

If you have (4) 4Ω dual voice coil subwoofers, you may need to wire the voice coils in parallel and the subwoofers in series to achieve optimal impedance.

Wiring these voice coils in series would increase the impedance of each subwoofer and then wiring the subwoofers in parallel would then reduce the impedance as it is spread across the drivers.

Depending on your amplifier’s stable impedance, the impedance of your voice coils, and the number of subwoofers in your build, you may need to wire in series and in parallel.

If you only have one dual voice coil subwoofer, you will either use series or parallel wiring.

When using a single 2Ω dual voice coil, wiring in parallel will reduce the impedance of the driver to 1Ω. Our amps are 1Ω stable.

While some individuals will wire Q Series amplifiers lower than 1Ω, doing so increases the likelihood of amplifier failure and is not covered under the warranty terms.

Need help wiring your dual voice coil subwoofers? Use our handy Online Wiring App.

Wiring batteries, circuits, or other electronics? The wiring practice will be fundamentally the same.

Next time, we will cover some of the more common reasons why subwoofers can break.