**Topic: Understand Ohm's Law for Car Audio**

**Click here to view our subwoofer wiring diagrams.**

# Wiring Car Subwoofers & Car Speakers Ohm's Law

It seems like one of the most common questions we
receive is: **What are Ohm's?** And how do it relate to a car audio system? The
most basic definition of Ohm's law states that the current through a
conductor between two points is directly proportional to the potential
difference (i.e. voltage drop or voltage) across the two points, and
inversely proportional to the resistance between them. Well what exactly
does all that mean?

I find that the easiest way to understand Ohm's law is
by a visual image. So lets say the diagram below represents a circuit.
First you would look at **potential voltage** which is represented as a body of water
in the diagram.
The voltage will always be the same in a car audio application. Twelve volts
would be your potential for any circuit in a standard car audio system. Next
the two different pipes represent resistance, notice they are different
sizes. The resistance
can greatly vary and that will determine how much current (amperage) can
flow though any given circuit. Resistance is measured in Ohm's. A very **high
resistance** allows a **small amount of current** to flow. A very **low resistance**
allows a **large amount of current** to flow. The larger pipe represents a lower
Ohm load than the smaller pipe. Next you can see the water flowing though
the pipes. That represents current (amperage). The larger pipe is able to
carry more amperage than the smaller pipe since it is rated at a lower
resistance. As pictured you can see much more water coming out of the larger
pipe. That is representing power which is measures in watts.

These are only the basics but for most car audio
applications it is enough to understand how and why you should wire an
amplifier or sub in a certain configuration. In a car audio application
you should **always run your equipment at the lowest possible Ohm load that an
amplifier, head unit or speaker can safely handle.** All amplifiers will
feature a rating which will usually look something like this.

- 500 Watts x 1 @ 4 Ohm
- 1000 Watts x 1 @ 2 Ohm

Now this is really important when purchasing equipment. To get the maximum output
out of the amplifier rating listed above you want to
make sure it is wired at a 2 Ohm load, running the same amplifier at a 4 Ohm
load will result in a **50% loss in potential power.** The same applies the other way around. You would not want to run
this amplifier lower than a 2 Ohm load otherwise you can potentially **burn it
up** since it would be running at twice the recommended power rating and
capabilities. Most amplifiers have a thermal protection
circuit however, it is still possible to damage the amplifier. Now if you look at my
diagram above you can really see how it works. The larger pipe
above would represent a 2 Ohm load whereas the smaller pipe would be 4 Ohm.
Every time an Ohm load is divided by 2 the current will double in amperage.
Every time an Ohm load is multiplied by 2 the current will be cut by half.

Next we will look at subwoofers and how to wire them
properly to the amplifier. Using the same amplifier ratings from above we now
know that we want to wire the amp at a 2 Ohm load. So how do we do that?
This is where things tend to get a little trickier however it is not as hard
as it may seem. There are two terms that you will need to know when wiring
subs or speakers, __Parallel__ and __Series__. Lets look at each
example before we figure out exactly how to wire our amplifier example from
above. Just remember **wiring in
series it is used to INCREASE the Ohm load** and **parallel is used to DECREASE
the Ohm load**. So an example of a series circuit can be viewed
below.

When wiring in series you are increasing the Ohm load by hopping from one voice coil to the next. So as you can see pictured the positive hops to negative on the opposite voice coil. To add this up you take the 4 Ohm load of each coil and add them together. So if you are wiring two Single 4 Ohm subs together you would add the two voice coils together sp 4 Ohm + 4 Ohm equals an end result of 8 Ohm. Moving on an example of a parallel circuit can be seen below:

When wiring in parallel you are decreasing the Ohm load and wiring the voice coils together. So you would run a lead from the positive voice coil on each sub to the opposite voice coil. In essence all the positives are connected on a single wire (conductor) and the same for the negatives. So if wiring two Single 4 Ohm subs you would take 4 Ohm and divide it by the number of voice coils. So 4 Ohm divided by two voice coils will equal a 2 Ohm load.

Okay now as you saw above the single 4 Ohm subs wired
in a parallel resulted in a 2 Ohm load, just what we needed for the
amplifier example from above. But the dual 2 Ohm subwoofers came to a 1 ohm
load that's too low, what do we do? You will normally have to use a **combination of series and parallel** to achieve the
correct Ohm load. Lets say you are running the amplifier I mentioned
above. That amplifier will need to run at a 2 Ohm load to achieve maximum
power. So if you decide you
wanted to run two subwoofers on that amplifier you would need to run either
**two single 4 Ohm** subwoofers or **two dual 2 Ohm** subwoofers. The two single 4
Ohm subs are easy to wire and you can see that in the diagram above. However, the
dual 2 Ohm subs will use a combination: first we wire each subwoofer in a **series** and then
wire them together in **parallel **at the amplifier. How do we do that? Lets go
over this in a diagram. Think of it as a two step process this will make it easier to figure out. So first you would take the subs and
wire them in series like below.

As you can see we now used a combination of first wiring each sub in series, and then we wired the subwoofers in parallel at the amplifier. This would be a typical installation and can be found in many installs. These are just a few examples but once you have the basics down you can figure out much more complex systems using the same methods.

Still can't figure out what you need? Click the links below to browse our
pre-made packages to achieve optimal power:

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