Voice Coils

• In electrodynamic speakers, the voice coil is a length of wire wrapped around a cylinder. The cylinder is positioned beside a magnet. When an electrical audio signal from an amplifier runs through the coil, it creates a magnetic field that changes depending on the sound the signal represents. This changing field reacts against the field from the stationary magnet. The coil moves as a result, pushing the cone of the speaker and reproducing the desired sound. Single voice coil speakers have a single wire wrapped around the cylinder, while dual voice coil speakers have two, giving them double the wiring terminals.
  
  

Parallel

• Unlike a single voice coil speaker, a dual voice coil speaker can be wired in parallel. This presents a lower impedance to the amplifier, which increases the power to the speaker. This is beneficial because sound systems run at their best efficiency when amplifiers provide a little more power than speakers require. One problem with this method is that some amplifiers are not designed to run at a lower impedance and may be damaged if wired in this way.
  
  

Series

• Dual voice coils can also be connected in series. This presents a higher impedance to the amplifier and provides less power to the speaker. The benefit of this method is that the speaker operates with less distortion, which improves overall sound quality. It also means that you can connect a second identical dual voice coil speaker in series and run both speakers on the same amplifier without presenting the amplifier with too low of an impedance to cause damage.
  
  

Independent

• It is also possible to connect each terminal of a dual voice coil speaker to the amplifier independently. This allows a single speaker to connect to both the right and left channels of the amplifier. The main advantage of this is that it enables you to connect a single subwoofer to your audio system and improve the quality of bass sounds without having to purchase two subwoofers. It is not advisable to leave one terminal disconnected from a dual voice coil speaker as this results in a drop in power efficiency.