Subwoofer Wiring Diagram: SVC vs DVC Voice Coils, Series and Parallel Impedance
This is a free printable subwoofer diagram: download the diagram as SVG or open it and print to paper or PDF.
A subwoofer wiring diagram shows how to connect single or dual voice coil drivers to an amplifier, calculating the final impedance the amplifier sees.
A subwoofer wiring diagram specifies the connections between the amplifier's speaker output terminals and one or more subwoofer drivers. The critical parameter the diagram determines is the total impedance the amplifier sees, because amplifiers have a minimum stable impedance rating — operating below this damages the amplifier.
Subwoofer drivers are manufactured as either Single Voice Coil (SVC) or Dual Voice Coil (DVC) types. An SVC driver has one voice coil with two terminals and one impedance rating, such as 4 Ω. A DVC driver has two independent voice coils wound on the same former, giving four terminals and two identical impedance ratings (e.g., 2 × 4 Ω or 2 × 2 Ω).
For SVC drivers, the wiring configuration choices are limited to how multiple drivers connect. Two 4 Ω SVC drivers wired in series (positive of amplifier to positive of first driver; negative of first driver to positive of second; negative of second driver to amplifier negative) produces 4 + 4 = 8 Ω total. The same two drivers in parallel produces 4 ÷ 2 = 2 Ω total.
DVC drivers provide more flexibility because each coil can be connected independently. A single DVC 4 Ω driver can be wired with its two coils in series (8 Ω total) or in parallel (2 Ω total). Two DVC 4 Ω drivers offer four coils and several combination options: all four coils in series gives 16 Ω; all in parallel gives 1 Ω; two pairs in series, those pairs in parallel gives 4 Ω.
The amplifier's stable impedance rating guides which configuration is appropriate. A mono amplifier rated stable at 2 Ω should not see a 1 Ω load; one rated stable at 4 Ω should not be loaded to 2 Ω. Most quality car audio mono amplifiers are rated at 1 Ω or 2 Ω stable.
Phase alignment between multiple drivers is important: all drivers must be wired in phase (positive terminals following the same polarity path from the amplifier). Out-of-phase drivers partially cancel each other's output at bass frequencies.
How to wire subwoofer diagram
- Identify your driver and amplifier specifications Note the subwoofer's type (SVC or DVC), its voice coil impedance rating(s), and its RMS power handling. Note the amplifier's RMS output power at relevant impedances and its minimum stable impedance. The final wired impedance must be at or above the amplifier's minimum.
- Calculate the target impedance Choose a wiring configuration that produces a final impedance at or above the amplifier's minimum stable impedance while maximising power delivery. For a 2 Ω stable mono amplifier and a single DVC 2 Ω driver, wiring coils in parallel gives 1 Ω (too low) — wire in series for 4 Ω, or confirm the amplifier is 1 Ω stable.
- Plan the connection diagram Draw the amplifier's positive and negative speaker output terminals. For series connection: chain drivers from amplifier positive, through each driver, back to amplifier negative. For parallel: run separate branches from the amplifier terminals to each driver.
- Verify phase alignment All drivers must be connected in phase. Trace the positive path from the amplifier: it should connect to the positive terminal of every driver in the circuit (accounting for series pass-through). A driver wired out of phase cancels bass output from its neighbours.
- Select and install speaker cable Use oxygen-free copper speaker cable of adequate gauge for the current involved. Longer runs and lower impedances require heavier gauge cable to minimise resistance losses. Keep cable runs as short as practical and equal length to each driver in parallel configurations.
- Make connections at the amplifier Connect the main positive and negative speaker outputs. Ensure the amplifier's low-pass filter crossover is set appropriately (typically 80–120 Hz for a subwoofer channel). Set the amplifier gain to match the head unit's output level, not to maximum.
- Test at low volume first Power the system and play bass test tones at low volume. Check for any clipping indicators on the amplifier. Verify the subwoofer is moving in phase with the mains speakers. Gradually increase volume while monitoring amplifier temperature.
Specifications
| Series impedance (two identical drivers) | Z1 + Z2 |
|---|---|
| Parallel impedance (two identical drivers) | (Z1 × Z2) / (Z1 + Z2) = Z/2 for equal values |
| DVC coils in series | 2 × single coil impedance |
| DVC coils in parallel | Single coil impedance ÷ 2 |
| Typical subwoofer low-pass crossover setting | 60–120 Hz |
| Typical subsonic filter setting (ported box) | 5–15 Hz above box tuning frequency |
| Amplifier fuse position (from battery) | Within 45 cm (18 inches) of battery positive terminal |
| Speaker cable gauge (recommended) | 12–16 AWG for most installations; heavier for high-power systems |
Safety warnings
- Automotive audio installation involves working with the vehicle's electrical system. Always disconnect the vehicle battery's negative terminal before making or modifying any wiring connections to prevent short circuits and potential fire.
- Fit an in-line fuse on the amplifier power cable within the shortest practical distance (typically within 45 cm / 18 inches) of the battery positive terminal. An unfused power cable running through the vehicle is a serious fire hazard.
- Do not operate the audio system at amplifier clipping levels for extended periods. Clipping causes the amplifier to produce a distorted waveform that contains high-frequency energy, which subwoofer voice coils are not designed to dissipate — causing premature failure.
- Ensure all cable runs through bodywork grommets are protected with appropriate grommets to prevent cable abrasion and short circuits against the vehicle chassis.
Tools needed
- Multimeter (impedance and continuity check)
- Wire stripper and crimping tool
- Screwdrivers (flat and cross-head)
- Panel removal tools
- Cable ties and loom wrap
- Drill with step bit (for cable pass-through holes)
- Phase tester (9 V battery method) for driver phasing
Common mistakes
- Wiring drivers in a configuration that presents a total impedance below the amplifier's minimum stable rating, overheating and destroying the amplifier's output transistors.
- Connecting one voice coil of a DVC driver out of phase with the other, so the two coils work against each other on the same voice coil former — reducing output and increasing distortion.
- Running an amplifier power cable without a fuse close to the battery, creating a potential fire hazard if the cable shorts against the chassis.
- Setting amplifier gain by turning it to maximum rather than matching it to the head unit's output voltage, causing the amplifier to clip at normal listening volumes.
- Underestimating current draw and using undersized power and ground cables, causing voltage drop that reduces amplifier performance and generates heat in the cables.
Troubleshooting
- Amplifier goes into protection mode
- Cause: Load impedance below minimum stable rating, short circuit in speaker wiring, or thermal overload Fix: Measure speaker output impedance with a multimeter (unconnected from amplifier). Verify impedance is at or above amplifier rating. Check for wire short between positive and negative at speaker terminals. Check amplifier ventilation.
- Subwoofer produces weak or no bass
- Cause: Drivers wired out of phase cancelling each other, gain set too low, low-pass crossover set too low, or poor ground connection Fix: Verify all driver positive terminals are on the same polarity path from the amplifier. Check amplifier gain setting. Set low-pass filter to 80–120 Hz. Check ground cable connection at amplifier chassis point.
- Distorted or buzzing bass
- Cause: Amplifier clipping, voice coil rubbing due to mechanical damage, or port tuning issue Fix: Reduce gain until distortion stops. Inspect driver cone for physical damage. If coil rubs, the driver requires repair or replacement.
Frequently asked questions
What is the difference between SVC and DVC subwoofers?
An SVC (Single Voice Coil) subwoofer has one voice coil and two terminals with a single impedance rating. A DVC (Dual Voice Coil) subwoofer has two independent voice coils on the same former, giving four terminals. DVC drivers offer more wiring configuration flexibility, allowing series, parallel, or independent amplifier channel connections.
How do I calculate the total impedance of two subwoofers wired in parallel?
For two identical drivers in parallel, divide the single driver's impedance by two. For non-identical drivers in parallel, use the formula: (Z1 × Z2) ÷ (Z1 + Z2). For example, two 4 Ω drivers in parallel give 4 ÷ 2 = 2 Ω. Always ensure the result is at or above your amplifier's minimum stable impedance.
What happens if I wire a subwoofer below my amplifier's minimum impedance rating?
The amplifier draws excessive current to maintain the output voltage into a lower-than-rated load, causing the output transistors to overheat. The amplifier will likely trigger its thermal protection and shut down, and repeated occurrences cause permanent damage to the output stage.
Why does wiring subwoofers in series produce less bass output than in parallel?
Series connection increases total impedance, which reduces current from the amplifier for a given output voltage, lowering the power delivered to each driver. Parallel connection reduces impedance, allowing the amplifier to deliver more current and more total power — with the important constraint that the result must not fall below the amplifier's stable impedance.
Can I connect a DVC subwoofer to a two-channel amplifier?
Yes. Each voice coil can be connected to a separate amplifier channel. This is useful when bridging is not an option or when a stereo amplifier is used in two-channel mode. Both channels receive the same mono bass signal (summed from the head unit). Ensure both channels are set to the same gain and polarity.