How to Wire a Dual Voice Coil Subwoofer (Series vs Parallel)
Wiring a subwoofer is where a lot of otherwise solid builds go wrong. Get the impedance wrong and you either leave power on the table or push your amplifier below its stable limit and cook it. Dual voice coil (DVC) subwoofers add flexibility - and one more chance to get it wrong - because you choose the final impedance by how you connect the two coils.
This guide covers what the coils actually are, the exact ohm loads for series and parallel wiring, how to match the result to your amplifier, and what wiring does (and does not) change about your sound.
What a dual voice coil is
A standard single voice coil (SVC) subwoofer has one coil and two terminals. A dual voice coil subwoofer has two electrically separate coils wound on the same former, giving four terminals: a positive and negative for each coil.
The two coils are mechanically identical and move the same cone. They exist purely to give you wiring options. By connecting them in series or parallel, you set the impedance the amplifier sees - without changing anything about the driver's mechanical behaviour or the box design.
A DVC sub is specified by its per-coil impedance: a "DVC 2-ohm" sub has two 2-ohm coils, a "DVC 4-ohm" sub has two 4-ohm coils, and so on.
Series vs parallel: the two rules
There are only two rules to remember.
Series: connect the positive of coil 1 to the negative of coil 2. The remaining two terminals go to the amp. Impedances add.
- Two 2-ohm coils in series = 4 ohms
- Two 4-ohm coils in series = 8 ohms
- Two 1-ohm coils in series = 2 ohms
Parallel: connect both positives together and both negatives together, then to the amp. Impedance halves.
- Two 2-ohm coils in parallel = 1 ohm
- Two 4-ohm coils in parallel = 2 ohms
- Two 1-ohm coils in parallel = 0.5 ohms
That is the entire decision for a single DVC sub. Series for the higher load, parallel for the lower load.
Single DVC sub: the full table
| Sub | Series | Parallel |
|---|---|---|
| DVC 1-ohm | 2 ohms | 0.5 ohms |
| DVC 2-ohm | 4 ohms | 1 ohm |
| DVC 4-ohm | 8 ohms | 2 ohms |
Two DVC subs: more combinations
With two DVC subs (four coils total) you have more ways to reach a target load. The two most useful for a pair of DVC 2-ohm subs:
- Each sub's coils in series (4 ohms each), the two subs in parallel: 2 ohms total
- Each sub's coils in parallel (1 ohm each), the two subs in series: 2 ohms total
- All four coils in parallel: 0.5 ohms total
- All four coils in series: 8 ohms total
The "series-parallel" combinations that land on 2 ohms are popular because 2 ohms is a common amplifier sweet spot, and they keep both subs at matched, balanced loads.
Single voice coil subs for comparison
If you have SVC subs, the wiring is simpler because each sub has only one coil:
- Two SVC 4-ohm subs: series = 8 ohms, parallel = 2 ohms
- Two SVC 2-ohm subs: series = 4 ohms, parallel = 1 ohm
Matching the load to your amplifier
This is the part that actually matters for reliability. Every amplifier has a minimum stable impedance - the lowest load it can drive safely. A "1-ohm stable" monoblock can drive a 1-ohm or higher load. Wire a 0.5-ohm load onto it and it will run hot, drop into protection, or fail.
The goal is to wire your sub (or subs) to a total impedance at or above the amp's rated minimum, and as close to that minimum as practical, because amplifiers make their rated power at their minimum stable load.
Worked example: you have a DVC 2-ohm sub and a monoblock rated 1000W at 1 ohm, 600W at 2 ohms.
- Wire the coils in parallel for a 1-ohm load and the amp delivers its full 1000W.
- Wire them in series for a 4-ohm load and the amp delivers far less than 600W (most class-D monoblocks roughly halve output for each doubling of impedance).
So with this amp, parallel wiring is the correct choice to get rated power. Never go below the amp's minimum - chasing more power by wiring below 1 ohm on a 1-ohm-stable amp is the most common way people destroy amplifiers.
What wiring does NOT change
Voice coil wiring changes the electrical load and therefore the power transfer, but it does not change:
- The box design. Volume, tuning, and port dimensions are unaffected. A sub needs the same enclosure whether its coils are series or parallel.
- The driver's mechanical behaviour. Xmax, cone area, and moving mass are fixed.
- The acoustic output for a given input power. At the same delivered watts, series and parallel produce the same SPL. The wiring only changes how many watts the amp can deliver into that load.
In other words: design the box around the driver, then wire the coils to extract the right power from your amp. The two decisions are independent.
How RokketBox models wiring
For multi-driver builds, RokketBox lets you model series and parallel wiring topology and shows the resulting system impedance curve across the frequency band. Because amplifier power scales with the load it sees, the impedance curve is what determines how much power actually reaches the cones - and the simulator plots it so you can see the load your amp will be driving at every frequency, not just the nominal rating.
Design your enclosure first in RokketBox using the driver's Thiele-Small parameters, confirm the response and excursion are where you want them, then use the wiring rules above to match your amplifier. If you are running multiple drivers, model the series and parallel topologies and compare the impedance curves to see which load best suits your amp's stable minimum.
For the parameters that drive the box design itself, see understanding Thiele-Small parameters, and for how power turns into heat and compression at the coil, see voice coil heating and power compression.