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How to Set Crossover Frequency for Car Audio System

Is there anything more liberating than blaring your favorite tunes while cruising down the highway towards your destination? Music and driving go hand in hand. No one can argue that!

Our car audio systems are an essential part of the overall driving experience. However, a car audio system only sounds best when everything is set correctly and in optimal working order.

Unbeknownst to many, integrating a crossover in your vehicle can make a night and day difference in terms of sounds quality.

So what are crossovers? How do they work? And how would you set a crossover frequency for your car audio system? Let’s find out…

What Is a Crossover and How Does It Work?

A crossover is essentially a network of filters that divide an input signal into two or more outputs of different ranges of frequencies, and direct specific frequency ranges to the appropriate speaker components. That way, tweeters, speakers, and subs will each get only the range of frequencies they were designed to play.

It goes without saying that every single car audio system has some sort of crossover. Even the most basic speakers come with a built-in 2-way crossover. Within each crossover, a high-pass filter blocks the lows but passes the high frequency notes to the tweeter, while a low-pass filter blocks the highs and passes low frequency notes on to the woofer.

Without a crossover, a messy, sonic “traffic jam” results. I mean, think about it, a crossover acts as an audio traffic cop, directing highs to your tweeters, midrange to your woofers, and low notes to your subwoofer. If there were no crossover in your system, your midrange and subwoofer would duplicate too many of the same frequencies and your sub would waste time trying to put out high notes it wasn’t meant to handle.

Furthermore, a “fatal pile-up” could also occur, with your tweets being destroyed by some renegade beefy lows thumping along in the wrong audio lane.

What Is A Crossover Frequency?

Simply put, a crossover frequency (AKA: crossover point) is the frequency at which sound transitions from one speaker to another.

In a two-way design, one filter (a high-pass) allows only the higher frequencies to pass through to the tweeter, and another (low-pass) routes only the low frequencies to the woofer.

The ‘crossover frequency’ is where these two filters overlap. It’s typically somewhere between 1 and 3 kHz, but it can vary broadly depending on the type, the physical size, and the design parameters of your drivers. This allows for a seamless sonic blend between the speaker channels and the subwoofer.

In a two-way system the crossover point often falls right in the middle of the critical vocal frequency range, and since both drivers (woofer and tweeter) are inherently reproducing the signal through the crossover region, this can result in some unwanted artifacts that become more prominent especially when listening off axis.

A three-way speaker system prevents this problem as the two crossover regions can be set below and above the critical vocal range.

Why Do The Speakers In Our Cars Need Crossovers?

First of all, it must be noted that music is composed of a bunch of audio frequencies that run the entire gamut of human hearing.

The main purpose of breaking music into regions (high, low and mid- range), and only sending certain frequencies to specific speakers, or “drivers,” is to achieve higher audio fidelity.

That said, car audio systems use crossovers because some speakers are better at producing specific frequencies than others. Tweeters for instance are designed to reproduce high frequencies, while woofers are designed to reproduce low frequencies, and so on.

So, by making sure that only the right frequencies are routed to the right speakers, you can effectively reduce distortion and help improve the overall sound quality of a car audio system.

Furthermore, crossovers help significantly with the weakness that’s inherent in small speakers. I mean, think about it, cheaply made speakers, especially small ones, can be terrible for playing bass, resulting in bad sound and unbearable distortion.

Additionally, crossovers are so helpful because they can help compensate for low and off-axis speakers mounting positions, engine and road noise.

Types of Crossovers in Car Audio Systems?

Crossovers come in two types, each of which is best suited to specific situations:

Active Crossovers

An active crossover sits between the receiver and amplifier and prevents the unwanted frequencies from reaching the amplifier, so that it doesn’t waste energy boosting them. This way, the amp can focus on only the frequencies it’s supposed to amplify.

Active crossovers can be adjusted to adapt to any speaker setup, because they divide the frequency range before amplification.

The term “active” means that the crossover needs to be powered to function. This type of crossovers are
more sophisticated and offer more control of the system’s tonal response over the whole audio spectrum.

Additionally, some active crossovers also include other sound-processing features like equalization for further tweaking of the sound to your personal satisfaction.

Active crossovers are mostly used in “active” sound systems where each driver (tweeter, woofer, sub) has its own channel of amplification.

Passive Crossovers

Passive crossovers are less sophisticated compared to active crossovers. They don’t need to get hooked up to a power source to function, which makes them relatively easy to install. However, there is a certain amount of inefficiency that is inherent in them.

Component systems and full-range speakers use this type of crossovers to filter out unwanted frequencies.

There are two kinds of passive crossovers: component crossovers that get wired between the amplifier and speakers, and in-line crossovers that sit between the receiver and the amp.

Component crossovers

Passive component crossovers step into the signal path right after the amplifier. In other terms, when a full-range signal exits the amplifier, it goes to the passive crossover which splits up the amplified signal into a lower-frequency signal range and a higher-frequency signal range, then sends the highs to the tweeter and the mids and lows to the woofer.

These crossovers consist of small networks of capacitors and coils, and are usually installed near the speakers.

Most passive component crossovers are featured with optional settings that let you attenuate the tweeter to better match the woofer volume.Since passive component crossovers deal with a signal that has already been amplified, they waste power, and release the unwanted parts of the amplified signal as heat.

In-line crossovers

In-line crossovers come in cylindrical shape with RCA connectors on each end and simply plug into your amplifier’s inputs.

The best thing about this type of crossovers, besides being inexpensive, is that they prevent your amplifiers from wasting energy amplifying signals you don’t want. The downside, however, is that they come set to a specific frequency and can’t be adjusted. This is not to mention the fact that they react differently to different amplifiers, possibly changing their crossover points unpredictably.

How to Configure Crossover Frequency for Car Audio Systems

Now that we’ve explained what a crossover is, how it works, and why car audio systems require one, let’s take a closer look at how to set crossover frequency in a car audio system.

Dialing the “right” crossover frequency takes a little time and effort. It’s a trial-and-error process that requires careful listening and a lot of precise tweaking and adjustments until you dial in the best sounding results.

It must be noted that there’s not a “perfect” set of crossover frequencies that work for every speaker in every vehicle. This is because nearly everyone is using different speakers, a different setup, not to mention that each vehicle has its own acoustical properties …etc.

However, here are some of the most common frequencies that work well in many cases. This is based on real world experience installing and working on different types of car audio systems.

Recommended Crossover Frequencies

Speaker/System TypeCrossover Freq. & Type
Subwoofers70-80 Hz (low pass)
Car main (full range) speakers56-60Hz (high pass)
Tweeters or 2-way speakers3-3.5KHz (high pass, or high/low-pass)
Midrange/woofer1K-3.5KHz (low pass)
3-way system500Hz & 3.5KHz (Woofer/tweeter crossover points)

Most modern car amplifiers are featured with high & low pass filters that you can use to improve the sound quality of your speakers.

P.S: When setting the crossover frequency, you don’t need to dial in the exact frequency right off the bat. You can just get it approximately right.

 

1. Setting the high-pass filter for the main speakers

Your main speakers can benefit a lot from using high-pass crossover, which allows frequencies above the chosen cut off frequency to pass through to a speaker or group of speakers. Thereby, reduce distortion, prevent bottoming out, and get more volume.

Here’s what you need to do to set the high-pass filter for your main speakers:

  • Turn off all EQ functions & bass boost before you make any adjustments
  • Set the crossover switch (if your amp has it) to the high-pass position
  • With a small screwdriver, turn the frequency all the way to the lowest setting
  • Turn the frequency dial to around 60-70Hz range

2. Setting the low-pass filter for subwoofers

A low-pass filter allows for bass frequencies below the chosen cut off frequency to pass through to a sub or group of subs. This will keep vocals vocals and other instruments out of the subwoofer channels and eliminate distortion.

Here’s what you need to do to set the low-pass filter for your subs:

  • Turn off all EQ functions & bass boost before you make any adjustments
  • Set the crossover switch (if your amp has it) to the low-pass position
  • With a small screwdriver, turn the frequency all the way to the lowest setting
  • Turn the frequency dial to around 70-80Hz range
P.S: In case your amplifier isn’t featured with adjustable frequency controls, but uses switches with fixed crossover frequencies instead, then you can set the crossover to the closest option available.

 

Keep in mind that setting up crossover frequency the way we described above isn’t by any means a bad thing, however, we do believe that this is one of those “rule of thumb” type things as every setup (box, subs, speakers, vehicle, …etc) has its own characteristics and specifications.

To help you fully grasp the concept of “crossover frequency”, let’s cover some good starting points for various system configurations.

P.S: You should always refer to your speaker’s manufacturer for more detailed information on their recommended frequency response.

 

System #1: Front Components (passive) & Subwoofer(s)

Recommended Starting Points:

  • Front Component Speakers – High-Pass Filter = 80 Hz (12 db or 24 db Slope)
  • Subwoofer(s) – Low-Pass Filter = 80 Hz (12 db or 24 db Slope)

Since component speakers use external passive crossovers, which will split up the frequencies between the tweeters and midrange drivers (or tweeter, midrange and woofer in case of a 3-way component set), a high-pass filter should be used to block out the lower bass frequencies that the midrange drivers can’t reproduce effectively.

As for the subwoofer, a low-pass filter should be used to block the high frequencies from being sent to the subwoofer.

As far as slope is concerned, 12 dB per octave and 24 dB per octave are the most commonly used slope options found in car audio systems. 12 dB and 24 dB represent what the filter does to frequencies past the cutoff point.

A 12 dB per octave slope is a more gradual cut off and is more suitable for vehicles such coupes or sedans that have the subwoofer(s) mounted in the trunk. The backseats act as a filter which absorbs upper bass range amplitude. The more shallow slope of 12 dB per octave will allow a bit more bleed through of frequencies above the filter frequency to help counter this.

A 24 dB per octave slope on the other hand is a more steeper cut off and is more suitable for open vehicles such as hatchbacks, trucks and SUVs, since the bass does not filter through seat material. Additionally, since a 24dB slope is a little harsh and is more like a cliff edge, it can sometimes allow for a slightly lower crossover point between the tweeter and midrange while still maintaining safety.


System #2: Front Components (w/ passive crossovers), Rear Coaxial Speakers & Subwoofer

Recommended Starting Points:

  • Front Component Speakers – High-Pass Filter = 80 Hz
  • Rear Coaxial Speakers – High-Pass Filter = 80 Hz
  • Subwoofer(s) – Low-Pass Filter = 80 Hz

This setup comprises of front component speakers and rear coaxial speakers, plus a subwoofer. It’s one of the most popular system configurations used in cars these days.

The crossovers for the front component speakers and subwoofer should be identical to system One (above). But since most coaxial speakers only come with a basic filter to block low frequencies from being sent to the tweeter, you’ll definitely need to consider adding a passive crossover to this setup. A High-Pass Filter needs to be applied to block out the lower frequencies.

If the rear coaxial speakers to use a passive crossover network, the crossovers should be set the same as the component speakers in system One.


System #3: Front 2-Way Components (active) & Subwoofer

Recommended Starting Points:

  • Tweeters – High-Pass Filter = 5,000 Hz
  • Midrange – Band-Pass Filter = 80 Hz HPF & 5,000 Hz LPF
  • Subwoofer(s) – Low-Pass Filter = 80 Hz

In this system, an electronic crossover is used to high-pass the tweeter, band-pass the midrange and low-pass the subwoofer(s).


System #4: Front 2-Way Components (active), Rear Speakers (passive) & Subwoofer

Recommended Starting Points:

  • Front Tweeters – High-Pass Filter = 5,000 Hz
  • Front Midrange – Band-Pass Filter = 80 Hz HPF & 5,000 Hz LPF
  • Rear Speakers (Passive) – High-Pass Filter = 80 Hz
  • Subwoofer(s) – Low-Pass Filter = 80 Hz

This system is a variation of System Three. It uses a subwoofer, fully active front speakers, and rear speakers with a passive crossover for rear fill. The rear speakers will only need 2 channels of amplification and a High-Pass Filter.


System #5: Front 3-Way Components (active) & Subwoofer(s)

Recommended Starting Points:

  • Tweeters – High-Pass Filter = 5,000 Hz
  • Midrange – Band-Pass Fiter = 500 Hz HPF & 5,000 Hz LPF
  • Woofers – Band-Pass Filter = 80 Hz HPF & 500 Hz LPF
  • Subwoofer(s) – Low-Pass Filter = 80 Hz

To create a more efficient front stage than the 2-way component set, this system uses 3-way component speakers that come with a pair of tweeters, small midrange speakers, and larger woofers.

That said, this setup will require a high-pass filter for the tweeters, two bandpass filters, one for the midrange and a second one for the woofers. A low-pass filter will be required for the subwoofer(s).


System #6: Front 3-Way Components (active), Rear Speakers (passive) & Subwoofer(s)

Recommended Starting Points:

  • High Pass (Front Tweeters) = 5,000 Hz (12 db or 24 db slope)
  • Band Pass (Front Midranges) = 5,000 Hz low pass – 500 Hz high pass (12 db or 24 db slope)
  • Band Pass (Front Woofers) = 500 Hz low pass – 80 Hz high pass (12 db or 24 db slope)
  • Low Pass (Subwoofers) = 80 Hz low pass (12 db or 24 db slope)

This system is a more involved variation of system #5. In addition to a 3-way active front stage and a subwoofer, it also includes a set of passive rear speakers. Therefore, since the rear speakers are using a passive crossover, only two channels of high-passed amplification will be needed.

P.S: The recommended starting points we listed here may vary broadly depending on a variety of parameters including the speakers being used, your listening preferences, and your vehicle’s acoustics. However, they should be looked at as ideal starting points.

What About Crossover Slope? Does It Make Any Difference?

Crossover slope is another important thing you should take into account when you’re setting the crossover frequency for your car audio system.

The slopes refer to the rate at which the crossover attenuates the blocked frequencies. They have different rates of roll-off.

Crossover slopes are rated in decibels per octave (dB/octave) in orders of 6 dB/octave, 12dB/octave, 18dB/octave…etc. The higher the dB/octave rating, the steeper the slope on the crossover.

Changing your crossover slope will affect power handing and overall frequency response of the speaker.

A 6dB per octave crossover for example reduces signal level by 6dB in every octave starting at the crossover point.

So, since an octave is double the crossover point (i.e: 20Hz –> 40Hz –> 80Hz –> 160Hz, etc.), every time the frequency of the audio signal is increased by one octave, the level of the audio signal will change by 6dB.

For example, if your low-pass filter is set at 80Hz with a 6dB slope, you’ll see a drop in level of 6dB at 160Hz. With slopes of 12dB and higher, you’ll hear little output beyond the crossover point.

Why Do Some Electronics Offer More Crossover Slopes?

Some car amplifiers, head units, and digital processors/equalizers offer more crossover options for serious audio tweaker listeners who want advanced control and like to constantly adjust and fiddle with the settings.

Having more crossover points will come really handy when you’re working on a high-end sound system. I mean, think about it, when bi-amping speakers (using two channels of amplification to power a single speaker), you can take advantage of each speaker’s natural behavior and get super-detailed control over the signals you send to the tweeters, the midranges, and the subs.

Alex Brown

Hey There, my name is Alex Brown, I'm an LA-based sound engineer with over 10 years experience installing, troubleshooting, and repairing commercial, automotive, and household sound equipment. I've installed highly competitive car audio systems, and everything from navigation systems to full car stereo systems, remote starters, alarms and beyond. I enjoy creating solutions and simplifying everyday needs. I also love helping people get great sounding gear, thereby, saving the world from bad sound one customer at a time.

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