How To Set Phase On Car Subwoofer And Car Amplifier (Solved)

A car subwoofer is an excellent addition for anyone looking to achieve great bass in their car stereo system. A subwoofer gives off deep, rich notes that add fullness to any music you are listening to.

However, buying a high-quality subwoofer is just the beginning of achieving the perfect bass in your car audio system. To get that perfect, consistent sound, you have to adjust the subwoofer’s phase, enabling it to move in sync with your car speakers.

Below is a comprehensive guide on how to adjust the phase on a car subwoofer and amplifier.

How to Set Phase on Car Subwoofer and Amplifier?

Setting the phase on the car subwoofer and amplifier is very important to get the best sound reproduced by your audio system. Turning on the music on your car audio system and adjusting the phase by turning the position of the phase regulator will allow you to set the phase on.

car subwoofer door panel

Here’s a step-by-step guide on how to set the phase on a car subwoofer.

Step 1: Turn on the Music on Your Car Audio System

It’s advisable to turn on some music when setting the phase on your car subwoofer.

Doing so will enable you to adjust the phase more accurately.

It’s also recommendable to play music with a clear bass sound.

Now, increase the amplifier’s gain until the subwoofer’s sound overpowers the speakers’ sound.

Step 2: Begin Adjusting the Phase By Turning The Position of the Phase Regulator

Now begin adjusting your subwoofer’s phase.

At this point, it’s advisable to have another person inside your car listening to the music playing. 

Adjust the phase until the person listening to the music in the car is sure that the bass sounds produced from both the subwoofer and the speakers are in sync.


Is There A Better Way To Set Phase on Car Subwoofer and Amplifier

car subwoofer enclosure boot

If you are still skeptical about this method of setting the phase on your subwoofer, there’s a more accurate method that will enable you to match your car speakers with the subwoofer. 

Here’s a step-by-step guide on to do so.

1. Match the Volume of The Subwoofer and Car Speakers

Begin by disconnecting your subwoofer from the car’s main speaker. Now try playing a test tone of the selected low-pass filter (LPF) value on the subwoofer at a low volume.

Keep adjusting the LPF level until the subwoofer and the main speaker has the same amplitude.

2. Change the Polarity of Your Main Car Speaker’s Connection

To change the polarity of your car speaker’s connection, you need to connect its positive wire to the negative terminal and the negative wire to the positive terminal. Remember to do this while the car audio system is turned off to avoid any accidents.

3. Adjust the Phase of The Subwoofer

Now, begin to increase the phase of the subwoofer. At this point, you’ll notice that the bass will gradually drop and then start to rise. 

Continue adjusting its phase until the main speaker and subwoofer play test tone out of phase but at the same level.

Keep on adjusting the phase until the level where the bass has the least amplitude, then set the phase knob at that position. Once you’re done, remember to connect the speaker’s wires to their correct terminals.

What Are the Benefits of Adding A Subwoofer to Your Car Stereo System?


Better-Quality Bass

The main advantage of having a subwoofer as part of your car audio system is that it gives off a better quality bass response. This reveals some sounds in your favorite music that your car’s main speakers alone cannot produce.

Typically, car speakers can only produce low frequencies up to about 50Hz. On the other hand, a subwoofer can produce low frequencies of up to 20Hz or lower.

In general, a subwoofer gives off a deep and precise bass response, enabling you to hear the deepest notes in the music you’re listening to, enhancing your entire car audio system.

Reduced Distortion

Subwoofers also significantly reduce distortion in the music you are listening to, especially if you are doing so at a high volume. Usually, when a car speaker produces low-frequency bass, its diaphragm and large cone can create distortion.

However, since a subwoofer is designed to produce lower frequencies, it enables you to listen to your music without any distortion, even at a high volume level.

Lesser Load on Car Speakers to Produce Extremely Low Frequencies

A car subwoofer lessens the burden on the speakers to produce low frequencies, allowing them to give off sounds in a more comfortable frequency range. As a result, your entire car audio system will be able to give off clear and precise sounds.

With that being said, let’s take a closer look at what phase setting is.

What Is Phase Setting on A Car Subwoofer?

Phase setting or phase control on a car subwoofer is basically adding an electrical delay to its incoming signal over a range of 0°-180°. Doing so enables your subwoofer to integrate perfectly with your car speakers.

If your car speakers and subwoofer are in phase, they will move forward and backward in sync, reinforcing each other’s output and producing high-quality, consistent sound.

On the other hand, if they are out of phase, the subwoofer cone will move forward while the main speakers will move backward or vice-versa, canceling each other’s output.

What Difference Will the Setting Phase Make on Bass?

As mentioned earlier, phase setting on a subwoofer delays its incoming signal over a range of 0°-180 °. This delay ensures that both your car speakers and subwoofer’s incoming signals sync with each other. 

Setting your subwoofer’s phase has a significant impact on the bass. When the speakers and subwoofer are in sync, you will get a good-quality bass.

Do You Need an Amplifier for A Subwoofer?

Usually, car subwoofers are connected to amplifiers equipped with phase controls/regulators allowing one to set their subwoofer’s phase.

An amplifier plays a significant role in a car stereo system in general. 

Let’s take a brief look at them.

Powers A Subwoofer

If you want to add a subwoofer to your car audio system, you’ll need an amplifier to power it. In most cases, a car stereo system may not have the connections specially designed for a car subwoofer. So, you’ll need an amplifier to power it.

Enables the Car Stereo System to Produce Sounds Without Any Distortion

Usually, a car audio system contains a built-in amplifier. However, this amp may not be powerful, causing the stereo system to produce distorted sounds when you play your music at a high volume. That is why most car stereo systems have various loudness controls that try and clear out that distortion.

However, these loudness controls lower the bass levels, which is a disadvantage. But, with an aftermarket amplifier, you can enjoy loud music with those deep, rich notes without any distortion.

Enhances Your Car Main Speakers’ Performance

Normally, most car speakers have low wattage ratings, which is why they cannot produce undistorted sounds, especially when you play music at high volume levels. This is where an aftermarket amplifier comes in.

An external amplifier provides more power to your car speakers, giving you more control over the treble, bass, and midrange frequencies that your main speakers produce. As a result, you can play loud music on your car’s audio system without any distortion.

Enables Your Car Audio System to Produce More Bass

Another advantage of adding an external amplifier to your car stereo system is that it gives more bass. With an aftermarket amplifier, your car speakers can produce deeper and louder bass.

What Tools/Equipment Will I Need to Set the Phase on The Subwoofer and Amplifier?

You may not need tools when setting the phase on your car subwoofer, as most subwoofers come with a phase control switch or knob that allows you to adjust it easily. If your subwoofer doesn’t have a phase control switch or knob, you can use a screwdriver to turn the phase control.

How Frequently Should I Adjust and Set the Phase on The Car Subwoofer and Amplifier?

There isn’t a specific amount of times you should adjust the phase on your car subwoofer. However, it’s advisable to do so as soon as you notice it’s out of phase. 

So how can one tell if a subwoofer is out of phase?

An out-of-phase car subwoofer will produce thin sound with little to no bass. The bass will not be as steady when music is playing.


It goes without saying that even the best quality subwoofer cannot produce precise and undistorted sounds if it is out of phase.

Setting phase on your car subwoofer enables it to be in sync with your car speakers, enabling your entire car audio system to give you the best sound experience.


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