While car speakers today are better than ever, nothing really does the job of digging deep like a subwoofer. Subwoofers are specially designed speakers dedicated solely to reproducing low frequencies – also known as bass. Adding a subwoofer to your car sound system is one of the most straightforward and significant improvements you can make to bring music to life in your car.
No matter what kind of music you like, or how softly or loudly you like to listen, a powerful subwoofer can reveal layers of sound that a typical “full-range” speakers are simply not equipped to handle.
Car subwoofers are manufactured with either a single voice coil (SVC) or dual voice coil (DVC). If you’re shopping for the best subwoofer for your car, you’ve probably wondered what the differences are between dual voice coil and single voice coil.
The basic distinctions here boil down to the number of voice coils a subwoofer has. A single voice coil has one winding coil, while a dual voice coil has two separate windings.
Dual voice coil subs are slightly more expensive than single voice coil subs, however, they offer more wiring options to better match and take advantage of your amplifier.
What is a Voice Coil?
The voice coil component of a speaker is just an electromagnet. And just like its name suggests, a voice coil comprises of a coiled wire wrapped around cylindrical shaped former made of magnetic metal, and is attached to the apex of the speaker cone and connected to the speaker driver terminals.
The voice coil moves in the gap of a permanent magnet and provides the motive force to the cone by the reaction of a magnetic field to the time-varying current that’s flowing through the coil. In other words, by running an electrical current through the wire, a magnetic field surrounding the coil gets generated; this field magnetizes the metal in the middle creating north and south polar orientations.
The cone of a loudspeaker moves with the coil, converting the electric current in the coil into linear cone motion, the latter produces a pressure wave.
Simply put, a voice coil is what makes a speaker a speaker. It puts up the electrical resistance and performs the work. Its resisting property is referred to as impedance and it’s measured in ohms. The lower a speaker’s impedance, the easier it is for an amplifier to supply power to it.
Subwoofer Voice Coils: Dual Vs Single
Technically speaking, the only difference between a single voice coil and a dual voice coil is that the former has one winding coil while the latter has two separate windings. And since both coils are energized, they perform the same as one with no difference other than wiring connection options.
Speaking of which, the multiple wiring options DVC subs offer make them a popular choice among car audio enthusiasts who want more freedom and flexibility in wiring their sound systems.
Parallel wiring means that the terminals of each sub are connected to the same things — plus to plus, and minus to minus. When multiple subwoofers or coils are wired in parallel, the formula for their total impedance is a bit complicated. When the impedances of all the drivers are the same, their total impedance, when wired in parallel, is that impedance value divided by the number of devices. For instance : four 4-ohm speakers wired in parallel have a total impedance of 1 ohm.
A dual 4-ohm voice coil subwoofer wired in parallel presents a 2-ohm load to your amplifier. Since an amplifier produces more power output at a lower impedance, the parallel wiring ensures you’ll get the maximum output out of your amplifier. In the same way, if you have an amp and two dual voice coil subs, wire both subs for 2-ohm impedance (one per channel) for maximum output.
Series wiring means that the subs are wired one after the other — a plus of one to a minus of another. To determine the overall impedance load of multiple subs wired in series, you simply add their impedances together. For example: Two 4-ohm subwoofers wired in series have a total impedance of 8 ohms.
Series wiring lets you configure multiple subwoofers to one amplifier at an acceptable impedance. Say for example you have two DVC subwoofers, wire both voice coils in series for an 8 ohm impedance, and then wire the two 8 ohm subs together in parallel for 4-ohm total impedance (perfect for bridging a two-channel amplifier). Another example: if you have a powerful 2-channel amp, wire four 8-ohm subs per channel (each amp channel is presented with a 2-ohm load).
If you have a dual voice coil subwoofer, and you prefer not bridge your amp, you can wire each voice coil to a separate channel of your amp. Independent wiring is a great option if you’re wiring two dual voice coil subwoofers to a 4-channel amplifier — one voice coil per channel. This should be taken with caution.
If a dual voice coil subwoofer must be wired to two independent amp channels, make sure the signal going to each coil is exactly the same, or the differences will cause distortion.
It must be noted that the voice coil differences have no direct effect on the subwoofer performance, frequency response, or power handling. A dual voice coil subwoofer does not directly perform better than the same subwoofer with a single voice coil.
A dual voice coil subwoofer performs the same whether it’s wired in series or parallel. Its power handling, frequency response, and other specifications do not change — the only difference is the impedance presented to the amplifier. As a result, you’ll need to use the enclosure that’s recommended for your sub, no matter how it’s wired.
DVCs and High-performance Amplifiers
Some power amplifiers are designed with an unregulated power supply. Because these amps have significantly different power ratings with different battery voltages, they’re the best way to go if you have a solid voltage source, and your electrical system can maintain a solid voltage at 14V or more.
This type of amplifiers are favored by car audio competitors for their impressive performance. An unregulated amp’s power output will significantly increase when it’s presented with a lower impedance load.
For example, an amplifier rated at 75 watts RMS x 2 channels at 4 ohms would double its power to 150 watts x 2 with a 2-ohm load. Therefore, Dual voice coil subs (particularly the dual 2-ohm models) give you the flexibility to wring every bit of power out of this type of amplifier.