Probably one of the things people have the most trouble with when installing multiple subs or dual voice coil subs is when it comes to wiring them to the amp. This post will explain what series and parallel wiring is, a little bit on Ohm’s law, the difference between single and dual voice coil subs, and how to wire subs to different Ohm loads.
If you don’t care about the technical stuff and just want to get to wiring, click here to be brought to the wiring diagrams page.
Series and Parallel Wiring
Series wiring for speakers means you are connecting the speakers like a chain. The positive terminal from one speaker to the negative terminal of the next speaker. Then the positive of that speaker to the negative of the next speaker. You can do this with an infinite number of speakers. In this arrangement, if one part of the circuit is removed, nothing will work.
In the case of speakers/subs, series wiring will add the impedance of each speaker together. For example: if you had three 2 Ohm speakers wired in series, the total impedance would be 6 Ohms. This will be explained in greater detail when I get to Ohm’s law.
For series wiring: Total Impedance = Sub Impedance x Total # of Subs
Parallel wiring connects all of the positive terminals together and all of the negative terminals together. This means if part of the circuit goes out, all of the rest will still be connected.
Parallel wiring of speakers reduces the resistance seen by the amp. So instead of adding all of the impedances together, the total impedance will be reduced further and further with each speaker added to the circuit. For example: if you wire two 4 Ohm subs together in parallel, you will get a total load of 2 Ohms.
For parallel wiring: Total Impedance = Sub Impedance / Total # of Subs, so if you have 4, 2 Ω SVC subs all wired in parallel, the total impedance will be 2 Ω / 4 subs = 0.5 Ω
Ohm’s law is the governing equation for all electrical circuits. The equation is: V = I x R where V=voltage, I=current, and R=resistance. For car audio, voltage is constant (12V), resistance is constant (the total impedance your speakers are wired to), and current will change depending on your impedance and the power your amp is capable of.
We can rearrange the equation to read I = V / R. Basically what this tells us is that if resistance is decreased, then the current the amp is pulling will increase, which in turn will increase the power output of the amplifier because of the power equation P = V x I. This is why wiring subs to lower impedances will get you more power out of your amp. This is also why a lot of amps don’t like seeing too low of an Ohm load since it will try to overpower the amp by pulling too much current.
This is a great Ohm’s Law chart to quickly see all the equations for power, current, voltage, and resistance:
Single vs. Dual Voice Coil
The only reason to get one over the other is for wiring options. Many people think DVC subs are more powerful than SVC or vice versa, but this is not the case. They make so many different versions of the same subs so you can get the total Ohm load you need no matter how many subs you plan on connecting together. Right out of the box, a single DVC sub has two different wiring options, whereas a SVC sub only has one.
Single Voice Coil (SVC)
Single voice coil subs are subwoofers that only have one voice coil. The impedance of a SVC sub will only be what that sub is rated at. For example, a single SVC 2 Ohm sub can only be wired to 2 Ohms.
Dual Voice Coil (DVC)
Dual voice coil subs have two voice coils. A single DVC sub can be wired to two different Ohm loads right out of the box. You can either wire it in series or parallel. For example: a single 4 Ohm DVC sub can be wired to either 2 Ohms (parallel) or 8 Ohms (series). The Ohm rating on DVC subs is actually the rating per voice coil, so you cannot wire a 4 Ohm DVC sub to 4 Ohms.
How to Wire Subs to Desired Impedance
So now that you know what series wiring will raise total impedance and parallel will drop total impedance, I will show you how this is used in subwoofer wiring. Whenever you have 2 SVC subs of the same impedance, series wiring will always double that number, and parallel wiring will always half that number. For all other cases, some math is needed especially when wiring DVC subs since you can have a mixture of series and parallel wiring in the same circuit.
For example: this circuit of two DVC 2 Ohm subs wired to a total load of 2 Ohms at the amp has the voice coils of each sub wired in series, but the two subs are then wired to each other in parallel. Wiring a DVC 2 Ohm sub in series gives you 4 Ohms. Then wiring two 4 Ohm subs in parallel will give you 2 Ohms. Hopefully that makes since.
If you have a multimeter, it is always best to double check your impedance after wiring before connecting your subs to the amp. I personally use this one from Amazon and it has worked great for me.
Here are some more diagrams for the most common wiring configurations. If you don’t see the configuration you plan on wiring, post a comment or send an email and I can help you out. Here is a link to just the wiring diagrams for easier access: http://caraudioadvice.com/subwoofer-wiring-diagrams/