How To Set Crossover Frequency For A Car Audio System

Dustin Hawley | Feb 10, 2021

If you are anything like most people, you enjoy playing the stereo in your car while you drive. Whether it’s listening to a podcast during your morning commute or cranking up the volume on your favorite songs, our car audio systems are an essential part of the overall driving experience.

car audio

A car audio system sounds best when everything is set correctly and in optimal working order. Unbeknownst to many, integrating a crossover frequency in your vehicle can make your sound system even better. So what are crossover frequencies? How do they work? And how would you set a crossover frequency for your car audio system?

While this may all seem a bit confusing on the surface, a detailed explanation of these terms will make it much easier to understand why crossovers make such a notable difference in our car audio systems.

What Is A Frequency?

In physics, frequency is defined as the number of waves that pass a fixed point in unit time. It also is defined as the number of cycles or vibrations undergone during one unit of time by a body in periodic motion. 

A “fixed place” can be any number of locations, including your headphones, speakers, amplifiers, or any kind of acoustic component. The frequency response shows how well a specific audio producer can reproduce all of the tones we can hear. 

Frequency is measured in the hertz (Hz) unit, and the hearing range of humans is from 20 Hz to 20 kHz. Frequency response is divided into three primary segments: bass, mid-frequency, and treble.

What Is A Crossover Frequency?

In the simplest terms, a crossover is a frequency at which sound transitions from one audio source to another, often a speaker. In a passive speaker, the electronic crossover components determine the sound transitions from the speaker channels to a subwoofer. 

Each speaker in your car audio system has a crossover frequency that is generally set in the AV receiver by a processor. This processor filters low-frequencies away from the speaker channels and redirects them to the subwoofer channel. This process is referred to as digital bass management, and it creates a seamless blend of sound between the subwoofer and the speaker channels. 

In many cases, crossover frequencies are set for each channel by the AV processor during auto-calibration. However, the crossover frequency can also be set manually when further optimization is necessary.

Why Do The Speakers In Our Cars Need Crossovers?

While our car speakers can blast our favorite tunes at the turn of a dial, they are not without their shortcomings. 

The most common speaker sizes installed at the factory are 3.5”, 4”, or 5.25”. These smaller speaker sizes allow for minimal bass reference, making it difficult to hear (or feel) your bass tones when playing audio. Even worse, they can distort the sound when you attempt to rectify the issue through manual EQ adjustments. Crossovers help because they block terrible-sounding audio frequencies that only cause problems. 

Crossovers are an electronic component circuit designed to react to specific frequencies. In laymen’s terms, every crossover can be set to the desired spectrum of sound where only frequencies within that particular range pass through. 

Types Of Crossover Frequencies For In-Car Audio 

There are three types of crossovers: 

  • Active (electronic) crossovers use solid-state components and are often built into amplifiers (but can also be purchased separately). The term “active” means that they need to be powered to function. 
  • Passive (speaker) crossovers don’t require a power source to function as active crossovers do. Instead, they sit between the amp and the speakers, where they filter out unwanted frequencies. Passive crossovers often come in the form of built-in speakers. 
  • Digital (software) crossovers work in the digital music domain. This type of crossover is implemented in the software code of car stereo head units. 

Keep in mind that there is not a perfect set of crossover frequencies that work for every speaker in every car. In nearly all situations, crossovers will require some form of adjusting to optimize their effectiveness. 

Recommended Crossover Frequencies

Depending on the exact type of speaker system in your car, these frequencies can vary slightly. But we’ve created a list of frequency ranges that will work well in most situations:

  • Subwoofers: 70-80 Hz (low pass), the most essential purpose of a subwoofer crossover is to block midrange sounds
  • Car main speakers: 50-60 Hz, the most critical element in main speaker crossovers is to block low-end bass (frequencies 80 Hz and below)
  • 2-way speakers: 3-3.5 kHz (high pass)
  • Midrange: 1-3.5 kHz
  • 3-way system: 300 Hz and 3.5 kHz

Setting The Crossover Frequency

If your car has a modern AV receiver that features an auto EQ program, consider yourself lucky. Vehicles that have this program will assign the proper crossover frequency automatically, so it’s best to leave those settings the way they are, as they are already specifically tailored to your car audio system. 

For vehicles without a modern AV receiver, setting a crossover frequency on your own takes a little time and patience. It’s a process that requires a lot of listening and tweaking until you dial in the best sounding results. 

Here are the steps for setting a crossover frequency: 

  • Determine your speakers’ frequency range. Play some music or audio with a dynamic frequency range (something with bass, mid-range, and high range sound). Listen to it play for a bit, and determine in what range currently sounds the best. 
  • Set the crossover point around 10 Hz below the lowest frequency your speakers can produce without issue. (keep in mind that the most common recommendation for crossover frequency is 80 Hz).
  • Once again, play some music. But this time, slowly turn up your receiver's volume until you hear it begin to distort. Just as you reach the volume level where the distortion starts, turn the volume down until the music sounds clean again and note the receiver's volume at that point. This value represents the volume threshold of your receiver.
  • Now set the gain of your subwoofer amp to its lowest possible value (a full counterclockwise position). From there, switch the low-pass filter on and set it as high (clockwise) as it will go. 
  • Play some audio. Listen and wait for a smooth transition between speakers and subwoofer. In an ideal case, you will not independently distinguish the bass signal; it should sound as if everything plays in unison. 
  • If you hear a bass bump when you set a crossover frequency, try adjusting the volume control until it matches your main speakers’ output. To do so, turn up the receiver's volume to its maximum, distortion-free position (the threshold). From this point, slowly turn up the gain on the subwoofer amp until the bass sounds balanced with the rest of the audio spectrum. 

Do You Need A Professional?

Though it may sound mildly complex, installing crossovers isn’t too complicated if you’re armed with the proper knowledge. Passive crossovers are relatively simple, as you’ll only need to wire a crossover between your amp and your speakers. On the other hand, active crossover installation requires a few additional steps and may require a certain level of expertise. Active crossovers require power, so you’ll have to run power and ground wires to each unit. If you are going the DIY route, the best thing to do is ground your crossover in the same place you grounded your amplifier. 

The answer to the question of whether you need a professional or not lies in your knowledge and experience working with car audio systems. Suppose you have little to no practical experience with installing car audio systems. In that case, we suggest you employ a car audio specialist’s services and have your crossovers set by professionals.

Summary

Understanding how to properly set a crossover frequency for your car audio system begins with a comprehensive knowledge of how your audio system is configured. The type of receiver and speakers you have will have a direct impact on your crossover frequency. Though we have outlined the basic steps, keep in mind there may be other recommendations that vary from those mentioned above. At the end of the day, fine-tuning is the most important element of a successful crossover. Let these recommendations be a general guideline, but note that the final settings are dependent upon your fine-tuning and the quality of sound you find most ideal.

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