How to Connect an Equalizer to a Car Stereo [Step By Step]

Since car audio equalizers aren’t absolutely necessary, it’s pretty easy to just gloss over the subject altogether when building or upgrading a car audio system.

We get it, there are a ton of things to think about when you’re building a car audio system. Head units, amplifiers, and speakers steal the spotlight, but, that doesn’t mean that equalizers aren’t important as well.

In fact, if you’ve ever wanted to have more precise control over the sound in your vehicle’s sound system, or if you’ve ever been frustrated that can’t get the music in your car to sound “just right”, you might want to think about investing in an equalizer.

Knowing how to wire an EQ for car audio systems can be a little confusing, but just relax​, we are here to help!

Even if you’re a relative greenhorn when it comes to car audio, the diagrams and the detailed steps below will help you accomplish this, no fuss, no muss.

What is an Equalizer?

First of all, equalization – or EQ – is one of the most well-known forms of audio processing. It allows you to change the balance of different frequency components in an audio signal by boosting or cutting certain frequencies.

An audio equalizer, or “EQ” for short, is simply a tool that allows you to fine tune the sound in your car to your liking. It provides additional tone adjustment beyond the standard treble, midrange, and bass controls available on most head units. These adjustments that an equalizer allows you to make are for specific ranges of sound known as ‘frequency bands’.

An equalizer will smooth out the unequal frequency response of your system by filtering many different frequency ranges, thereby eliminating unwanted distortion and allowing for a more balanced sound.

All in all, an equalizer will allow you to feel like a master audio technician when you hit that sweet spot for your ears.

How Does an Equalizer Work?

An equalizer is a device that’s made up of multiple filters that isolate specific ranges — or bands — centered around specific frequencies. It changes the quality of the audio tone that passes through it by using these filters. These filters adjust, or gain, the frequency ranges of the audio signals. These adjustments can be positive gains called “boosts,” or negative gains called “cuts.”.

For example, graphic equalizers divide sound between 6 and 31 bands of frequency, and have a row of vertical slider controls on the face whose positions mirrors the frequency response curve the device is applying. The more sliders you have, the smaller the frequency band per slider you can manipulate.

An equalizer makes the signal better by “Cleaning” it up. So if, for example, the treble is too loud on a track, you can use the equalizer to attenuate the amplitude of one or two of the higher frequency bands to soften it. Similarly, if the bass is shaking everything inside the vehicle, you can lower the slider of one of the lower frequency bands.

Do You Need an Equalizer?

Well, let’s start off by saying that there’s no car audio system that doesn’t need some form of equalization. Does this mean that an equalizer is a must?

Well, Not really. An equalizer isn’t absolutely necessary for the average Joe. However, having one will come in really handy especially for a seasoned audiophile. It’ll adjust your music to match the acoustic qualities of your car.

An equalizer helps as much as you know how to use it. In other words, it’s well worth it once everything is setup properly.

It should be noted, however, that the only way an EQ is going to help you is if you have the knowledge and the ability to properly tune it, and take the time to do so. Otherwise, it will just add insult to injury and make things worse.

When properly used, a good equalizer will make a night and day difference in terms of sound quality. It’ll allow you to cater to your listening preferences, and give you ultra-precise tone control required to restore great sound which usually gets disrupted by your noisiest, most hard-to-handle component — your car.

Because no car is acoustically perfect, a good equalizer can fine-tune even a high-end system.

Vehicle noise, road noise, surface shapes, surface materials, distances from speakers to these surfaces, speaker placement …etc all affect your system’s sound and chalk up together to make some frequencies sound muffled and muddy regardless of how powerful your components are.

An equalizer is what you need to remedy each one of these problems, and tune your sound to match the acoustics of your specific car – it’ll boost the frequencies you’re missing and attenuate those your vehicle exaggerates.

Besides giving you tight tonal control over your music playback, an equalizer is also a great way to protect your equipment. For example, if your bass is handled by a pair of 6.5 inch subwoofers, you can use your equalizer to cut back all frequencies below 40-50 Hz. This will allow your amp to work more efficiently and most importantly, you’ll get higher, cleaner volume while protecting your speaker drivers from tones they can’t handle.

What is the Purpose of an Equalizer?

To put it simply, an equalizer is responsible for manipulating frequencies. It works by attenuating unwanted frequencies and/or boosting others, all to balance out sounds so they work well with one another.

It’ll greatly enhance the quality of your vehicle’s stereo system by separating your music into several frequency bands, and allow precise adjustments to be made to these bands. These adjustments compensate for the acoustics of your vehicle’s interior and for road noise to provide you with custom-balanced, high-quality sound.

Where to Install an Equalizer

First and foremost, an equalizer can be installed anywhere between your amp and receiver.

Some equalizers are designed to be mounted in the dash while others are designed for a remote location such as the trunk. The installation location will depend on your particular choice of equalizer and preferences.

Generally speaking, you need to make sure you equalizer is easy to get to so that you can make adjustments without much trouble.

Some people mount their equalizers in the trunk near the amp. This makes sense especially if you have more than one amp. It will also make it a lot easier to add additional amps down the line.

In some cars, you can easily fit the equalizer somewhere in/under the dash using a mounting bracket. Mounting your equalizer in the dash will give you easy access to the controls continuously.

When installing your equalizer, it’s highly recommended that you don’t mount it directly onto a conductive surface of the vehicle — you will invite noise problems. Instead, mount it on a non-conductive board and attach the board to the car body, or at the very least use rubber grommets under the mounting screws to isolate the chassis.

How Do You Hook Up an Equalizer to a Car Stereo? (Diagram)

Although the process of installing and tweaking your equalizer may be lengthy and slightly difficult, especially for greenhorn car audio enthusiasts, the end result is well worth it for any serious audio fanatic who desires superior sound quality.

To make the whole process as straightforward as possible, we’ve pulled together this step by step guide that will show you how to wire your equalizer to your car stereo.

Step 1: Making the Power Connections

1.1- Connect the Power Wire

Cut a length of 16 gauge wire long enough to reach from the equalizer location to your vehicle’s fuse box. Strip one end of the wire and connect it to the EQ’s power input.

Depending on your equalizer, this may require a crimp-on connector, or bare wire might be sufficient.

Next, route the wire from the device’s location to your car’s fuse panel. Using a fuse tap, connect the wire to a source of switched 12V power.

You can also connect this cable to your receiver’s power cable. If your receiver does not have a wiring diagram to show which wires are switched power cables, you’ll need to use a multimeter to figure it out.

So, connect the multimeter to the cable when the key is in the off position and make sure the voltage reads zero. Then turn the key into the on position and see if the multimeter reads 12V. If it does read 12V when the ignition is on and reads Zero when the ignition is off, then you have found the correct switched 12V power wire.

Now, all you need to do is to use a razor blade knife to strip the insulation off a small section of the radio’s power wire, and strip the other end of the EQ’s power wire, splice them together, and wrap the exposed metal with electrical tape.

Alternatively, you can use a quick slide connector such as “Tap-In Squeeze Connector”, or “T tap wire connector” to easily tap into the power wire of your receiver. This method doesn’t require any cutting or splicing.

1.2- Connect the Ground Wire

To ground your equalizer, use the crimping tool to crimp a ring terminal to one end of a length of 16-gauge wire, and then bolt the terminal tightly to the vehicle’s metal chassis. Make sure the grounding point is sanded down thoroughly to bare metal and scraped clean of any paint or primer.

If you can’t find a convenient ground screw or bolt, then you will have to drill a hole in the chassis — be very careful not to drill into the gas tank or brake line while doing this.

1.3- Connect the Remote Turn on Wire

The turn-on wire (also called the remote wire) is responsible for telling your equalizer to turn on whenever the stereo is powered up (usually, whenever the ignition is in the ACCESSORY or ON position).

On the receiver, this turn on wire should be a blue (usually blue but can be other colors) wire that goes to the amplifier.

The receiver’s turn on wire receives a 12v DC signal from the electrical system of your vehicle car whenever it’s turned on.

For your equalizer to turn on when the receiver is powered up, you’ll need to tap into your in-dash receiver’s amp turn-on lead to get a turn-on signal for your device.

So, unmount the receiver from the dash to access the turn-on wire, strip the insulation off a small section of this wire, then strip the insulation off another small-gauge cable that’s long enough to reach from the receiver to the equalizer, after that you can either splice, crimp, or solder the wires together to make a connection. You can also use a Posi-Connector to make it an easy job.

Last but not least, wrap the solder or crimp connection with electrical tape to prevent electrical shorts.

Step 2: Making the Signal Connections

Now, the last step in wiring an equalizer to a car stereo is making the signal connections. To do that, you’ll need use a set of RCA patch cables that’s long enough to be routed from your head unit’s preamp outputs to the inputs of your equalizer.

So, while your receiver is out of the dash to access the turn on lead, connect a set of RCA cables to the head unit’s preamp outputs (long enough to reach your equalizer in its mounting location), then run the RCA cables through the dash to the equalizer and connect them to the EQ inputs.

Connecting the RCA jacks on a car equalizer:

• Main RCA inputs: Connect these to the receiver’s front RCA jacks.
• Front RCA outputs: Connect these to the crossover’s main RCA inputs. If you’re not using a crossover connect them directly to your amp’s front RCA inputs.
• Rear RCA outputs: Connect these to the crossover’s rear RCA inputs. If you’re not using a crossover, connect them to your amp’s rear RCA inputs.
• AUX input RCA jacks (optional): Some equalizers come with an AUX input to let you directly connect your phone’s headphone jack, an MP3 player ..etc to the equalizer. So, you can connect this to a 3.5mm stereo headphone to RCA cable as needed. Equalizers that come with feature have a front panel switch which allows you easily change between sources.

How to Connect an Equalizer to a Car Stereo with No Rca Jacks

Even if you car stereo isn’t equipped with RCA jacks (which is the case with factory car stereos) you can still hook it up to an equalizer using a line output converter.

A line output converter (or LOC for short) is a device that converts speaker-level output signals (high-level amplified signals required to drive speakers) into RCA preamp-level signals (low level signals) that an equalizer, crossover, or car amplifier can use.

How to Connect Crossover to Equalizer for Car Audio (Diagram)

Like a crossover, the equalizer gets installed between your receiver and your amplifier. If you’re going to be using both an equalizer and a crossover together, the order of connection should be:

1. First, the receiver’s outputs go to the equalizer’s inputs
2. Second, the equalizer’s outputs go to the crossover’s inputs
3. Third, the crossover’s outputs go to your amplifier’s inputs

Like an equalizer, a crossover needs power, ground (negative), and remote turn-on wires.

• The power wire on your crossover should be connected to the radio’s memory wire or another power source that has a constant +12V (does not change with the ignition switch).
• The ground wire should be attached to the vehicle’s chassis or the same ground wire as the car stereo.
• The remote turn-on wire should be connected to the car stereo’s turn-on wire (blue wire). Alternatively, you can connect its to a +12V accessory wire that turns on & off with the ignition.