Last updated on March 17th, 2021 at 09:37 pm

Picking the right size of wire for your car audio project is probably the most important decision that affects the safety of your build, equipment and even the quality of your sound. When you wire up any car audio project, incorrect wiring size can lead to fires, overheating components, blown fuses, and tons of frustration. You will save time and money by doing the job right and using the correct wiring for your application. This article will explain the different sizes of wire, types of wire, and how to correctly wire any car audio project for professional results.

Wiring Size Standards

Most of the world uses a standardized sizing system to identify differences between wires. The system is called the American Wire Gauge (AWG). Wire gauge is a source of confusion and frustration for many people. The important thing to remember is that smaller AWG numbers indicate a larger wire size. So, 18-gauge wire is smaller than 14 gauge wire, and so on.

That’s only part of the picture though. The standard was created to describe solid, round wire. Today, stranded copper or copper clad aluminum are much more common. The AWG standard is still used, but the minute air gaps around the stranded wire is not counted. This means that an 18-gauge stranded wire will have a larger outside diameter than an 18-gauge solid wire.

Stranded wire will include two numbers after the AWG size. These refer to the number of strands and the size of each wire in the strand. For example, a 22 AWG 7/30 wire is seven, 30 AWG wires bundled into a 22 AWG wire.

There is a lot of debate about whether a higher number of strands improves audio performance. In general, a higher number of strands is less important than starting with the correct gauge. A higher strand count will typically mean a more flexible cable. Solid core cables being the least flexible since it’s a solid strand of copper inside.

When you are buying wiring for your project, these three numbers will give you a good indication of whether the gauge you are buying is going to work well for your application.

Resistance, Distance, and Impedance

There are a few things that you’ll need to consider when purchasing wiring in addition to the standards and gauge. All wire has some level of resistance, measured in Ohms. Wire manufacturers list resistance-per-foot. A lower resistance means more available power. While there is a standard for wire resistance-per-foot, a low-quality wire can increase resistance and cause audio distortion.

Since resistance is measured per-foot, the longer a wire is, the more resistance it will have. In most automotive applications, the length of a speaker wire is of little concern simply because the distances are almost always less than 25 ft. Longer runs will require larger gauge wire to handle the additional resistance.

Impedance is one of the most important numbers you’ll find on a speaker. In order to create a good-sounding system, you have to match the impedance of each speaker to one another and to the amplifier that’s powering it. Impedance is also measured in Ohms and functions like resistance within the speaker. The impedance of a speaker doesn’t affect the size of speaker wire, though.

Choosing the Right Speaker Wire

Speaker wire is typically two separate stranded wires molded together with one strand indicating positive polarity. The wire is designed so installers can easily separate the two wires to make connections to speakers while keeping the length of the wire in one piece.

Unfortunately, there are a lot of gimmicky speaker wire products out there promising better audio quality at a higher price. There is no scientific evidence to indicate that using speaker wire branded as “Audiophile-quality” or “Professional-quality” speaker wire gives you better sounding music.

Buying the Right Speaker Wire

The real thing to look for when buying speaker wire is quality. It’s very common to find speaker wire that is labeled as 16 AWG but is actually much smaller. Buying speaker wire from a reputable company makes the biggest difference. We like to use speaker wire sold by Crutchfield. The wire sold by Crutchfield meets the Consumer Technology Association (CTA-2015) standards for size, resistance, and quality of insulation. Plus, the price is pretty good, too.

Sizing Wire for Speakers

Low power, factory-style car audio speakers will work fine with almost any size wire in a normal application. It’s because the power demands of the speaker are far below the power carrying capabilities of the wire. Upgrading from factory speakers to high-power aftermarket speakers with high(er) powered amplifiers is when you will often require changing speaker wiring to a larger gauge. In order to supply more power, the wire must be of a sufficient size to carry the load.

What you will need to factor is how much power you will supply to your speakers with. Smaller units, like door or dash speakers that only require a max of 50 watts RMS or less don’t need wiring larger than 16 AWG and will function just fine with 18 AWG speaker wire. If you are planning on providing amplifier power in the neighborhood of 225 watts RMS, 16 AWG is necessary.

Subwoofer Wiring

While most door and deck speakers will work just fine with almost any type of wire, subwoofers have much higher power demands. When wiring your subs into an amplifier, 12 AWG wire is preferable, but 14 AWG can handle most applications.

Crossover Wiring

Using an active crossover is an excellent way to give yourself control over your car audio experience, but there is significant confusion about how to properly wire it up. Active crossovers require 12 v power, but you can use a wire as small as 18 AWG because the demands from the crossover are low.

Both passive and active crossovers require connections from the amp to the car speakers. All you have to do is use the same size of wire you would normally use for the amount of power you’re sending to the speaker.

Wiring an Amplifier

One of the main culprits for sub-par car audio performance is improper amplifier wiring. Car Amplifiers require lots of power, and the bigger the amp, the more power it needs. If you run too small of a wire to power your amplifier, you run the risk of damaging the amp, melting wire, and even starting a fire.

In order to figure out how big of a power cable your amp needs, you’ll have to gather a few figures. First, you’ll need to calculate the entire RMS wattage of the system. Then, you need to figure how long the cable will be from your battery to the amplifier.

Once you have these figures at hand, use the handy chart below to find the best wire size for your application. Sometimes, your total amps and length of wire will fall somewhere between two sizes. Always round up, not down.

Wire Size Calculator with length, amperes and wire gauge breakdown
*Note that this is only for Copper wire only

Grounding Connections

Probably the leading cause of all car audio system problems are bad grounds. Ground wires should mount securely to clean, unpainted metal or dedicated ground points. Ground wires should be appropriately sized for the application- larger amperage draws need to have a larger ground cable. Typically the gauge of the power cable is matched with the ground cable.

Making Good Connections

The biggest mistake anyone can make when installing wiring for car audio systems is to make bad connections between wires. Faulty connections can cause all sorts of problems from interference to sound cutting out. Poorly made connections on power wires create shorts and can damage components.

Some people will argue endlessly about the pros and cons of different types of connectors. The truth is, no matter how you connect wires, the connection needs to be solid. There are no consequences of using crimp connectors in car audio wiring if it’s done properly with the proper tools. While it is possible a small amount of resistance is introduced, a secure crimp connector won’t affect your sound quality.

Soldering wires to connect them can provide a more secure method, but success depends on the soldering skills of the installer. Poorly soldered connections can lead to corrosion, wires breaking, and all sorts of failures.

Shrink wrap is the best way to protect connections from dust and dirt. Shrink wrap will also help keep wires from pulling apart. Crimp connectors are even available that have shrink wrap sleeves to really speed up installation.

Don’t go Too Big or Too Long

So, what happens if you run too big of a gauge? The good news is, there isn’t any harm in too big of a cable. The reasons not to go too big are practical. First, larger cable gets expensive quickly. Second, it’s difficult to conceal bundles of large wires behind factory panels and under carpets.

When you run cable to speakers, don’t coil extra lengths of wire up. Just cut it off and make your connection. Coiled wire adds unnecessary resistance and can actually create impedance much like a speaker coil. It’s also sloppy.

Conclusion

Picking the correct size of wire for your car audio project is important. While all the different sizes of wire out there can be confusing, and it’s easy to get bogged down in a project trying to select the correct size wire to go with your components. The most important wire to pay attention to the size of is power leads for amplifiers. You must select the appropriate wire for power leads, or your system will have problems.

More than anything, making solid wiring connections is the most important thing when installing car audio equipment. Almost all problems with stereos can be traced to a faulty connection between wires or a bad ground.