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How to Wire Car Speakers to the Radio Without the Harness?

If you wonder whether a radio wiring harness is necessary for connecting your speakers to the head unit and are not sure what to do if you do not have one, this article is for you.

There are a couple of methods that you can use to connect speakers without the harness, and they are relatively simple.  

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When your car radio does not have a harness or when either existing harness or wires are damaged, the easiest way to connect speakers is by using a car radio harness adapter. The harness adapter has to be plugged into the back of the radio and then speakers connected directly to the colour-coded wires on your radio.

As an Amazon Associate, ImproveCarAudio will receive a small commission from qualifying purchases made through the links in this article.

The article below will detail every aspect of a harness and speakers, considering all necessary factors when connecting them to your radio.

This will include what a harness is, do you need one, can speakers be secured without a harness, how to connect speakers without a harness, various methods to do so, car stereo specific wire specifications such as colour, as well as speaker wire gauge and length. 

Understanding a Wiring Harness

When you try to connect your car speakers without a harness (although not difficult), you can consider one because of their affordability and availability, even for aftermarket systems such as speakers and radios.

You even get smaller harnesses that function to serve as a separate mini version allowing you to add additional wiring or make configurations if you need to.  

wiring car speakers with radio without harness

Do I Need a Wiring Harness to Install Car Speakers?

A wiring harness makes connecting car audio wires straightforward. A harness can house as many as 15 wires (a standard car radio) or even more if your car houses an infotainment DIN or double DIN unit. It would be a daunting task, especially at the manufacturing level of motor vehicles, to have to wire components by hand to one another all the time. Hence this little device that supports the whole system was created. 

Harnesses can also be used for specialized situations where simple connection types and connectors such as crimp connectors just won’t work.

Depending on what car stereo system you have and what components it comprises, connecting your speakers without a harness will not be too difficult.

Keep in mind that a harness is not too expensive, and they are relatively easy to find, even if you need a specific one. You can contact the manufacturer of your car radio and ask them who their suppliers are, and you can contact a used-car-parts store and try to find one there. 

However, you do not essentially need a harness to connect car speakers with the radio.

Are Speaker Wires a Part of a Car Radio Harness

Speaker wires are the largest part of the harness connections. A standard car radio harness with 15 connection points will dedicate up to 8 connection points just for your speakers.

This is because your car radio or amplifier will usually have four channels of two speakers each (front and rear), and each channel has to have a positive and negative terminal. 

Does a Wiring Harness Add Any Additional Functionality?

The role of a harness is relatively straightforward. It has to electrically connect electrical devices and electrical components that are installed within your car. Hence, a harness can be used for most elements in your vehicle, such as the lighting system, fans, air conditioners, radio, and so on.

A wiring harness is made of many individual wires that play specific roles. These can include sending constant power, trigger devices, transmitting information, or remote steering for other devices.

Do All Car Stereos Have the Same Connectors (Connection Types)?

All car stereos will most likely have the male connection type and the female type you can purchase, or it would otherwise be connected to your car. Furthermore, all aftermarket car stereos can use the same harness

How Do I Know Which Speaker Wires Are Which?

All car radio and audio systems are now colour-coded to a specific standard, so you know which cables are in which colours. There will always be the same colour for the same wire no matter what car or radio you are trying to modify. 

What Is a Car Stereo Wires Color Code?

For the most part, the car radio and harness will come with eight wires for each speaker, and these are the colours we want to focus on when connecting speakers:


The grey wires are used to connect the right front speakers to your stereo. The grey wire is positive, and the grey/black is negative.


The white wires connect the left front speakers to your car radio. The white wire is positive, and the white/black wire is negative.


The purple wires connect the right rear speakers to your car radio. The purple wire is positive, and the purple/black wire is negative.


The green wires connect the left rear speakers to your car radio. The green wire is positive, and the green/black wire is negative.

You need to remember this color combination when you connect your speakers to your radio. If you connect the speakers to the incorrect wire, the audio will play from the incorrect speakers, which in reality means that you can hear, for example, both front speakers on your left side.

Should You Cut the Car Radio Wiring Harness?

This only applies if you have a new radio and need to install it. When you purchase a new radio or head unit for your car, it will most probably come with a harness already fitted to it with a male-type connection on the end of it. This harness will probably have quite an extended length.

A new radio or head unit comes with such a long harness because some vehicles need a longer cable length to reach the section or sections of their car to plug it in.

There is nothing worse than purchasing a new radio or head unit to find out the cable’s length is just shy of where it needs to connect.

However, some cars are designed to house the radio and a smaller area of wiring. What you should do then is cut your harness and solder it back together so you do not have to cram a large amount of wiring in the small allotted area.  

The soldering process is straightforward, and you do not need to be a professional to solder one or two wires. One thing to take note of is that if your harness has fuses or noise filters on them (this could be from the constant wire), then it is advised that you cut the harness beyond these points (but only for these wires) so you can keep those components fitted as they are indeed there for a reason.

How to Wire Your Car Speakers to the Radio Without a Harness

There are several ways to connect speakers with the car stereo, and they do not need any exacting knowledge or understanding of car circuitry or audio systems in general. 

What factors should you consider before you connect your speakers to the radio without a harness?

Even though connecting speakers to your car radio is a pretty straightforward task, there are a handful of things you should consider so you get the job done right the first time around. 

Where is the amplifier in the head unit?

It does not matter what audio system you have or where the audio system is. All audio systems at their core use the same principle. You firstly have a sound source (in our case, the car radio). The source is the device that will send the audio signal, which is of a low level to the preamp that will convert the low-level signal into a line level. 

All radios will have a preamp built into them, so you do not have to worry about that. The preamp then sends the signal to a powered amplifier, where the signal is then boosted and pushed out through your speakers.

Is it a built-in amplifier?

Depending on your car audio system setup, your standard factory OEM radio may have a built-in amplifier. This is not uncommon, and then the possibility of you being able to wire your speakers to your car radio remains. 

If you have replaced your car radio with the one you have purchased, make sure it has an amplifier built into it. Otherwise, you would need the additional setup to add an external amplifier to your car audio system. 

Is it an external amplifier?

If your car audio system has an external amplifier, you will not be connecting your speakers to the radio, and in this case, a harness would be unnecessary.

This is because the speakers will connect directly to the terminals in the amplifier. 

Since technology is ever increasing in today’s world, car manufacturers sometimes implement external amplifiers in their standard OEM factory audio setup. Depending on how the amplifier is built and designed, you would connect the wires from your speakers to it directly. 

The same for aftermarket car amplifiers. What you have to do is to connect the radio outputs (RCA outputs if it was an aftermarket radio) into your amplifier and connect your speakers to your external powered amplifier by way of speaker wires and the amplifier’s high-level terminals.

Considering Speakers That Have No Harness.

Typically speakers will not come with a harness. If they are purchased as aftermarket speakers, they probably won’t even include speaker wire unless you buy them in some bundle package. 

As I just mentioned, you need to know how your audio system is installed:

  • Are you replacing existing speakers that are connected to your radio?

These are all factors you need to consider, and with speakers, you need to know if the wire runs to an external amplifier or the radio. 

The only thing you will need to purchase, if necessary, is speaker wire, and depending on where they are in your car, you would need to consider the correct length and gauge, which could be a few feet. 

How to Choose Car Speaker Wires?

Suppose you need to choose your speaker wire and purchase some. In that case, a wire gauge will play a role because of your amplifier’s power and distance away from the speakers (in this case, we are assuming that you are not connecting to an amplifier but rather your radio). 

One thing to note is that the higher the gauge, the thinner the wire. Usually, you can be sure that your system would need between 18 and 12 gauge wires, depending on a few factors. The 18 gauge will be the thinnest wire you would need, and the 12 gauge would be the thickest and will preferably be used for the subwoofer (this is for most standard applications).

A thick wire would be recommended for speakers with low impedance levels (2 ohms) where the wire is relatively long and the power passing through it is relatively high. Hence, consider 12 to 14 gauge wire.

A thin wire would be recommended for speakers with a higher (or standard) impedance level (4 ohms) and run in a relatively short distance. In general, when the distance is less than 50 feet, you do not have to worry about increasing the wires’ thickness.

Considering your radio that has no harness.

The radio in your car should be fitted with a harness, whether it is a standard OEM factory radio or an aftermarket radio. As we said, a harness helps connect devices of a car (a radio) to other sections of the vehicle more quickly and easily, and all modern cars and aftermarket systems have them implemented for user-friendliness. 

Before you jump into your vehicle and start ripping at wires behind the dash, follow the radio leads to see if they eventually run into a harness.

If you purchased a car stereo without a harness, you can still connect your speakers to your car radio without a harness, and we will cover the various ways below. 

What Options Do You Have When Trying to Connect Your Car Speakers to Your Radio Without a Harness?

We are now assuming that you do not have an external amplifier in your car audio setup and that the speakers will run to your radio that can power the speakers. We will then also assume that you have no harness attached to your radio for some reason. When considering these factors, there are three things you can do to connect your speakers to your car radio without a harness.

Buy a Replacement Harness for Your Car Radio.

Harnesses are relatively cheap and inexpensive. You get various sizes and shapes and can most likely find one that fits your radio model if you do not have one or yours is not working correctly. 

This would make things more comfortable if you later intend to purchase a new radio. Otherwise, you would have to go through the process of wiring everything up again, which would include your speakers. We will not detail how you would connect a harness in this article, but the principles used below are the same if you would like to connect a harness to your wiring system. 

You Can Use a Soldering Method to Connect Your Speakers to Your Radio.

The best way to connect your speakers to your radio is by soldering your radio wire to your speakers’ wire and using heat shrink tubing to seal the wires and keep them together. I am having a great soldering experience with using a simple Iron Kit. It is available on Amazon, so check the latest price now.

This method is preferred because there is less room for error once the wires are soldered and connected, and also soldered connections are more robust. This means they won’t break or fault quickly. It is a huge hassle to remove a dash and radio just to get to one loose wire. 

All you would do is strip either end of your speaker wire and radio speaker wire, placing the heat shrink tubing around the wire before soldering them together.

After you have soldered both wires, you would use a heating device (a hair dryer works well) to seal the heat shrink tubing around the soldered area of the wire. 

You Can Use a Crimp Clamp to Connect Your Speakers to Your Radio.

If you do not want to play with hot temperatures, you can crimp the wires together. Just purchase Amazon terminal connectors designed to hold two wires together, creating a connection.

These little fittings that can be bought and used for car audio systems are called crimp clamps. The principle is the same as using a soldering iron to fuse the wires. However, in this case, you just need these little clamps and a crimping device to squeeze the ends down tightly. 

What you would do is again strip the wires on both ends of the speaker wire and the radio speaker wire and then push each end of the wires into the crimp clamp. All you would do then is crimp both sides of the device, and the cables would be held securely in place. 

As a final note, just remember in all instances when connecting your speakers to a radio, keep the colour-coded system that tells you which wire is for which speaker in mind. 


We determined that it was pretty straightforward to connect your speakers to your car radio without a harness because a harness is just a type of device or system that aids in connecting wires more efficiently for our purposes using a little plastic connector. 

A harness is not necessary for wiring devices together. The only factor you really need to consider is what method you want to connect the speakers with the stereo. 

Lastly, the two methods of connecting your car speakers to the car stereo are either soldering or using crimp clamps. Both techniques are simple and can save you money on the expert. 


How to Install a Car Radio Without a Wiring Harness?

A wiring harness adapter is commonly used in aftermarket installations, but when it is not available, connecting all wires will be complicated.

To connect the car radio without a harness right, follow the steps below:

#1. Unplug the car battery to avoid shocks while working on your car stereo.

#2. Find your serial radio harness and unplug it from the back of your radio.

#3. Find all of the wires that need to be connected to the back of your new radio. You will need a wire for each function, including:

  • Power (constant 12V+)
  • Ground
  • Ignition switched power (12V+ when the key is in the “Run” position)
  • Illumination or dimmer control (usually a brown or yellow wire)
  • Power antenna (remotely turns on your radio’s power antenna)
  • Left front speaker (+)
  • Left front speaker (-)
  • Right front speaker (+)
  • Right front speaker (-)
  • Left rear speaker (+)
  • Left rear speaker (-)
  • Right rear speaker (+)
  • Right rear speaker (-)

#4. Your new radio will likely have a spot to plug in the serial radio harness, but if it does not, you will need to cut and splice the wires to connect them.

#5. Wrap any exposed wire with electrical tape to avoid short circuits.

#6. Once all the wires are connected, plug in the car battery and test your new radio.

#7. If you install a new car stereo, you will also need to purchase a dash kit and car stereo installation kit. These kits will help you install your new radio without damaging your car’s dash.

How to Wire Car Speakers to the Radio?

To wire car speakers to the radio, you need to strip the end of the speaker wires and connect them to the corresponding cables coming out of the stereo.

When connecting, make sure to check which wires are positive and negative.

An incorrect connection will make speakers play in the reverse polarity, which negatively affects the audio experience and can cause damaging some sensitive speaker types.

How to Wire Aftermarket Radio Without Harness?

If you install a new aftermarket radio, I do not recommend installing it without the harness.

You will need to purchase a dash kit and car stereo installation kit. These kits will help you install your new radio without damaging your car’s dash.

Once you have all of the necessary parts, follow the instructions that come with the dash kit and installation kit to install your new radio.

If you are unsure how to properly install your new radio, consult a professional installer. Improper installation can damage your car’s electrical system and void the car radio’s warranty.

How to Wire Car Speakers Without Harness?

To wire car speakers to the radio without a harness, you need to strip the end of the speaker wires and connect them to the corresponding cables coming out of the stereo.

When connecting, make sure to check which wires are positive and negative.

How to Straight Wire a Car Radio to the Battery?

To connect the radio straight to the battery, you have to put together the yellow wire with the red one and run it to the positive battery terminal.

You have to run the black (ground) wire to the negative battery terminal.

Such connection is possible and often used, especially in older cars, but the radio is more difficult to control, and it may drain your battery overnight if you forget to turn it off.

A better solution is to wire the stereo to an ignition switch so that it only has power when the car’s engine is on.