What Is A Good Crossover Frequency For Home Or Car Audio Speakers?

What is good crossover frequency featured image

Crossovers are one of the single most helpful parts or features for getting great sound in car or home audio systems. However, using them the right way can leave you scratching your head if you don’t know the basics.

On that subject, what is a good crossover frequency for speakers in your car or home audio system? That’s what you’ll learn here.

In this article I’ll explain:

  • How crossovers work and why they make a big difference
  • The best crossover frequencies for car audio amps, speakers, and subwoofers
  • Recommended crossover frequencies for small, medium, and large home stereo and home theater receiver speakers including subwoofers
  • What to know about crossover slopes and which you should use

Let’s get started so you can enjoy better sound right away!

Contents

The basics: What does a crossover do? What does crossover frequency mean?

Crossovers and crossover frequencies explained diagram

People tend to talk about crossovers as if they totally “block” sounds you don’t want to go to your speakers. While they sort-of do, in reality, crossovers aren’t blocks but instead filters that greatly reduce the output level of certain sound frequencies sent to speakers.

How are crossovers helpful for speakers?

Diagram of man listening to speaker with crossover vs without a crossover

Crossovers are very important for audio as they help us deal with the weaknesses of commonly available speakers as well as poor installation environments. For example, some of the most common speaker sizes used in cars such as 3.5″, 4″, and 5.25″ sizes can be terrible for playing bass. They end up with bad sound and ugly distortion when driven with low-end bass and more power.

To make matters worse, many speakers aren’t used in proper enclosures. This ends up giving poor sound and distortion at higher volumes because they leak air and don’t properly trap sound waves like others. That means they can “bottom out” easily if driven hard with music with “thump” and hard bass.

An excellent solution to these and other problems is to completely remove that area of sound that causes poor sound quality. This lets you drive the speakers with more power yet get more clarity and volume from them – even cheap speakers!

2-way and 3-way speakers become possible

Additionally, 2-way and 3-way speakers rely on crossovers to act as a divider between the speakers, resulting in excellent sound thanks to limiting the range of sound each produces.

Understanding crossover basics

When we think about musical signals we don’t always realize the important things going on behind the scenes. In fact, you’ll almost never find a good-sounding speaker system that isn’t using one or more crossovers; that’s how important they are for great sound.

A crossover is an electrical or electronic component circuit made up of parts that react to certain frequencies and is designed to prevent unwanted ranges of sound from reaching speakers.

Crossovers allow a desired range of sound to pass unaltered and effectively block ranges of sound past a limit called the cutoff frequency.

A crossover circuit can be used for a single speaker channel or combined with others to separate and direct sound to others, too. In car and home audio, the most common speaker crossovers are used in 2-way coaxial speakers, component speakers, and 2-way speaker cabinets.

There are 3 types of crossovers you’ll find in home or car audio:

  1. Active (electronic) crossovers – work in the signal path (line-level signals)
  2. Passive (speaker) crossovers – work in the amplified speaker path after an amplifier
  3. Digital (software) crossovers – they work with sound in the digital music domain

Electronic crossovers

Electronic crossover functional diagram showing the basic blocks of operation

Active (electronic) crossovers use tiny signal amplifier chips called op-amps (operational amplifiers) to act similar to much bigger and far less efficient speaker crossovers.

Not only are they much smaller in size, but they can also be designed to allow you to choose between using no crossover, a high-pass, or a low-pass filter easily using a slide switch. Unlike passive crossovers, they do require power to work and change the signal, hence the name “active.”

These types work with low-level (RCA) signals either before an amp’s RCA inputs (in add-on external crossovers you can buy) or inside the amp. The signal output of an electronic crossover has to be amplified, unlike speaker (passive) crossovers that you connect between an amp and speakers.

That means you’ll still need to use an amp to drive speakers with them.

Speaker crossovers

Home and car stereo speaker crossover examples illustrated and labeled

Examples of car and home speaker “passive” (non-powered) crossovers. These are circuit boards using electrical components to block unwanted sound frequencies from going to speakers not best for producing them. This effectively separates splits the incoming sound signal into 2 or more and sends them to the speakers as needed.

“Passive” crossovers are those that use inductor and capacitors, without a power source, to filter out sounds you don’t want to reach speakers. They’re typically used for smaller speakers like with tweeters, 2-way coaxial speakers, and home theater 2-way speakers because they’re cost-effective and can deliver great sound.

Passive speakers aren’t used to block midrange and treble (“highs”) from subwoofers because the size of the inductors needed would be really big – and expensive, too! They’re also much less efficient than electronic ones in that case.

Electronic crossovers are typically used in subwoofer amps because of the cost and size savings – as well as better sound altogether.

Digital (software-based) crossovers

Example of home stereo digital subwoofer crossover menu display

This type is implemented in the software code of home theater receivers, car stereo head units, or digital audio processors. Software-based crossovers usually work by implementing math-based functions that alter the signal output based on its frequency.

It’s a really complicated topic, but the basic concepts aren’t hard to understand. By using special formulas, not only different types of crossovers but also equalizers can be implemented and operate on the musical signal when its represented as a binary digital number.

This is a cost and space-saving feature as there are few, if any, parts needed to make it work. However, it usually takes more specialized microprocessors or digital signal processor (DSP) chips to do so.

Crossover frequency vs music range chart

Crossover audio range chart diagram

Within the range of sound your ears can hear, for most cases crossover frequencies typically fall into a small range you’ll likely use for tweeters (high-pass), full range speakers (high-pass), and subwoofers (low-pass).

The truth is, there’s not a “perfect” set of crossover frequencies that work for every speaker in every vehicle. That’s basically impossible because nearly everyone is using different speakers, a different setup, and so on.

However, here are some of the most common frequencies that work well in many cases. 

What are good crossover frequencies for home audio?

Man teaching about good crossover frequencies for home audio

Since different people have different needs, I’ll cover the general best crossover frequencies for ome stereos and home theater receiver speakers in a table below.

One thing to remember is that these are general guidelines that should fit most people’s needs. However, just like anything else, what sounds good to one person or with one home audio system might not sound good for another.

Feel free to try out and adjust the crossover levels recommended here for what sounds best to you. Ideally, the crossover speaker frequencies (for example, for the main speakers and subwoofer) will blend seamlessly and there won’t be any “gaps” in the sound. If there are, you’ll need to keep tweaking it until that problem is removed.

TIP: I recommend you set any equalizers, bass boost, or “loudness” controls to off before adjusting the crossovers to be sure those don’t interfere during adjustment.

Home stereo crossover frequency table

Speaker/System TypeCrossover Freq. & TypeNotes
Subwoofer 80 Hz (low pass)

Good low-pass frequency range for subwoofer bass & blocking midrange sounds. Best for pure, clear bass sound that "hits." *For THX Certified/non THX Certified 80 Hz is advised, but test 80-120H for the best sound.

Tower/main front speakers [4", 5.25", or 6" woofers] 60-80Hz (high pass)

Blocks low-end bass that causes distortion & speakers to "bottom out." Great compromise between full-range sound and midrange bass capability. Works best complimented with a subwoofer.

Tower/main front speakers [8", 10" or larger woofers] 40Hz (high pass) or "flat" (full-range)

Larger woofer cones are usually much better at handling deeper bass. Also, home theater surround systems normally send very low bass to the subwoofer as well.

Small center, surround, or bookshelf 100-120H (high pass)

Many surround or center speakers use drivers not suited for lower bass - only midrange and above.

Mid-sized center, surround, or bookshelf 80-100Hz (high pass)

Better suited for playing bass notes slightly below vocals and notes around 100Hz, but not good for lower bass.

Large sized center, surround, or bookshelf 50 or 60-80Hz (high pass)

Larger speakers of this type can often handle a bit more bass nearly down to, but not including, the subwoofer range. Try 50Hz for larger woofers and 60-80Hz for others if unsure.

On-wall or mini satellite/surround type speakers 150-200Hz (high pass)

Many can't produce much bass but instead midrange and above. May distort badly if sent low bass notes so be sure to use a HPF as recommended.

What are good crossover frequencies for car audio?

Man teaching about good crossover frequencies for car audio

Car audio speakers are somewhat different from home audio in that they often suffer from terrible enclosures which aggravates the problems they have when producing certain sounds. The crossover frequencies below are general guidelines that work well in most cases but be aware you may need to tweak them.

For example, small speakers with no real enclosure may have horribly “thin” sound – in that case you may need to raise the high-pass filter (HPF) frequency even higher to minimize sound problems. Use these as a starting point, see what you get, and go from there.

TIP: Disable any equalizers, bass boost features, or “loudness” controls to off before adjusting the crossovers to be sure those don’t interfere during adjustment.

Also, be aware that a crossover can’t compensate for a subwoofer that’s poorly matched to a speaker box. It’s very important for good bass sound to have subwoofers in an enclosure of the right size and quality.

Car audio speaker & amp crossover frequency table

Speaker/System TypeCrossover Freq. & TypeNotes
Subwoofers 70-80 Hz (low pass)

Good low-pass frequency range for subwoofer bass & blocking midrange sounds. Best for pure, clear bass sound that "hits."

Car main (full range) speakers 56-60Hz (high pass)

Blocks low-end bass that causes distortion or speakers to "bottom out." Great compromise between full-range sound and midrange bass capability.

Tweeters or 2-way speakers 3-3.5KHz (high pass, or high/low-pass)

Most 2-way or 1-way (tweeter) crossovers use a frequency near this as most tweeters can't handle sounds below this range. Same for woofers above this range.

Midrange/woofer 1K-3.5KHz (low pass)

Woofers and many midrange speakers do not perform well above this general range. They're poor for treble and a tweeter should be added.

3-way system 500Hz & 3.5KHz (Woofer/tweeter crossover points)

Similar to 2-way systems the upper freq. would be the same. Midrange drivers in a 3-way system often do not perform well below 500Hz or 250Hz in many cases.

What is a good crossover slope? Does it matter?

What crossover slope do you need image of man thinking

In some cases, you can choose from a number of slopes (the steepness of the cutoff) on your amplifier or other components. As I mentioned earlier, the slope controls the steepness of a crossover filter, or how strongly it reduces & blocks sounds you don’t want to reach your speakers.

And as I mentioned earlier, -12dB per octave (“-12dB/octave”) is very common for both car and home audio systems. While it may seem like the rule of “more is better” applies here, the truth is that most of the time a 12dB/octave crossover slope is all you’ll need.

I’d had some success using an 18dB/octave slope with subwoofers, but aside from that, it won’t usually make much of a difference – at least not enough you’ll take notice of.

Here are a few tips to help:

  • I don’t recommend a -6dB/octave crossover for speakers, especially small main ones. That’s because a 6dB slope still allows a lot of bass to pass when using tweeters and small speakers.
  • 12dB is almost always fine. 18dB is fine too, but you likely won’t notice much difference in most speaker systems.
  • Don’t spend extra money, time, or effort for a more advanced crossover unless you really need the features. The majority of the time, even for amplified speaker installations at home or in the car, a standard crossover works great when properly set up.

Why do some car or home audio components have different slope settings?

Close up image of a car amp crossover controlsExample of a car amplifier without crossover slope options. If it’s not labeled near the controls, it’s nearly always a 12dB/octave and you’ll be fine.

It’s not unusual for home & car audio stereos and amps to offer 6dB, 12dB, 18dB, and even steeper (ex.: 24dB) crossover slopes you can choose. That’s especially true for mid to high-end equipment. The extra selectable crossover slope options allow more advanced control and flexibility when working with custom audio systems.

For example, when bi-amping speakers (using an electronic crossover and separate amp channels for the tweeter, the midrange speaker, and so on), you can take advantage of eliminating waste and any audio interference a speaker crossover may cause by driving them directly without a crossover.

That can give you some of the best sound possible if you’re really wanting to pursue high-end sound using more advanced techniques.

What is a good crossover slope for car audio and home audio?

However here the best crossover slopes for most people:

  • A 12/dB setting is good and will do the job in most cases for subwoofers (low-pass) and full-range speakers (high-pass).
  • However, 18dB/octave can be better for some subwoofers depending on your particular subwoofer, the enclosure, and how your vehicle alters the sound. In that case, experiment using the -18dB setting and see how it sounds.
  • 6dB/octave is a bit poor and will allow sounds to pass that can “muddy” the sound and just isn’t good enough for bass speakers. I don’t recommend it in most cases.

The main goal is to have the same sound filtering at the same crossover frequency. The goal is to have the sound put out by the speakers match up perfectly so there’s neither much overlap nor gaps in the sound between the speakers.

I don’t think I’ve installed a home or car audio speaker system yet where the -12dB per octave wasn’t able to do the job well.

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How To Set Crossover Frequencies For Your Car Audio System

How to set crossover frequency for car audio system featured image

Crossovers are awesome for getting better sound from even cheap speakers. But what are crossovers, how are they helpful, and what are the best crossover settings for car audio?

In this article I’ll show you how to set crossover frequencies for your car audio system along with some other helpful info:

  • How crossovers work and why they make a big difference
  • The best car audio crossover frequency settings (table is provided)
  • Diagrams to show you how to set your car amp crossovers

…and much more, too. There’s a lot to cover so let’s get started!

Contents

What does a crossover do? Crossover frequency, slopes, and more explained

Crossovers and crossover frequencies explained diagram

People tend to talk about crossovers as if they totally “block” sounds you don’t want to go to your speakers. While they sort-of do, in reality, crossovers are filters that greatly reduce the amount of unwanted sound frequencies sent to speakers.

How are crossovers helpful for speakers?

Crossovers are very important for car audio as they help us deal with the poor enclosures they’re used in along with the weaknesses that small speakers have. Some of the most common speaker sizes installed from the factory or sold for aftermarket use like 3.5″, 4″, and 5.25″ sizes can be terrible for playing bass, resulting in bad sound and ugly distortion.

To make matters worse, speakers in cars, trucks, and even boats are often mounted in areas where it’s impossible to get great sound because they leak air and don’t form a good enclosure to deliver sound properly unlike home stereo speaker cabinets. That means they leak air badly and can “bottom out” easily if driven hard with bass sounds, for example.

One reason why crossovers are so helpful there is that we can use them to block terrible-sounding audio frequencies that ordinarily would cause these problems and others, too.

Understanding crossover basics

Car audio crossover examples

When we think about musical signals we don’t always realize the important things going on behind the scenes. In fact, you’ll almost never find a good-sounding speaker system that isn’t using one or more types of crossovers; that’s how important they are for great sound.

A crossover (audio crossover) is an electrical or electronic component circuit made up of parts that react to certain frequencies and designed to eliminate unwanted ranges of sound from reaching speakers.

Crossovers allow a desired range of sound to pass unaltered and effectively block ranges of sound past a limit called the cutoff frequency.

A crossover circuit can be used for only one single speaker channel or combined with another to separate and direct sound the best speakers suited to produce it. In car audio, the most common speaker crossovers are used in 2-way coaxial and component speakers.

Simple speaker crossovers can also be added inline with speakers to block lower-end bass as well.

What are the 3 types of crossovers in car audio?

There are 3 types of crossovers:

  1. Active (electronic) crossovers – work in the signal path (line-level signals)
  2. Passive (speaker) crossovers – work in the amplified speaker path after an amplifier
  3. Digital (software) crossovers – they work with sound in the digital music domain

1. Active (electronic) crossovers

Illustrated diagram of an electronic (active) crossover example

An example of an external (add-on) electronic (active) 2-way crossover. These are basically the same as the electronic crossovers built into many amps you can buy today. Some offer a few more options, but unlike years gone by, they’re less and less important these days. Most amps today include what you’ll need already.

Active crossovers use electrical components such as transistor-based chips called op-amps (operational amplifiers) to behave the same way as their much bigger and much less efficient speaker crossover counterparts.

They offer a lot of benefits (especially their compact size) and can be designed to allow you to choose between using no crossover, a high-pass, or a low-pass easily. Unlike passive crossovers, they do require power to work and change the signal, hence the name “active.”

Active crossovers work with a line-level (RCA) signal either before an amp’s RCA inputs (in add-on external crossovers you can buy) or inside the amp. The signal output of an electronic crossover has to be amplified, unlike speaker (passive) crossovers that you connect between an amp and speakers.

2. Passive (speaker) crossovers

Image showing speaker crossover examples and resistor, capacitor, and inductors

“Passive” crossovers are those that use inductor and capacitors, without a power source, to filter out sounds you don’t want to reach speakers. They’re usually used for smaller speakers like with tweeters, 2-way coaxial speakers, and component speaker systems because they’re relatively affordable in those situations.

Passive speakers aren’t used to block midrange and treble (“highs”) from subwoofers because the size of the inductors needed would be really big – and expensive, too! They’re also much less efficient than electronic ones in that case.

That’s one reason the built-in low-pass subwoofer crossovers in amps are so great.

3. Digital (software-based) crossovers

In dash car stereo with equalizer shown

Software-based equalizers and crossovers use advanced software routines to alter sound in the “digital domain.” That means they can alter the sound (or filter it, as crossovers do) by working only with the digital musical signal. This makes them more complicated but saves spaces & money since it reduces size & the electronics required.

This type is implemented in the software code of home theater receivers, car stereo head units, or digital audio processors. Software-based crossovers usually work by implementing math-based functions that alter the signal output based on its frequency.

It’s a really complicated topic, but the basic concepts aren’t hard to understand. By using special formulas, not only different types of crossovers but also equalizers can be implemented and operate on the musical signal when its represented as a binary digital number.

This is a cost and space-saving feature as there are few, if any, parts needed to make it work. However, it usually takes more specialized microprocessors or digital signal processor (DSP) chips to do so.

What are good crossover frequencies for car audio?

Crossover audio range chart diagram

Within the range of sound your ears can hear, for most cases crossover frequencies typically fall into a small range you’ll likely use for tweeters (high-pass), full range speakers (high-pass), and subwoofers (low-pass).

The truth is, there’s not a “perfect” set of crossover frequencies that work for every speaker in every vehicle. That’s basically impossible because nearly everyone is using different speakers, a different setup, and so on.

However, here are some of the most common frequencies that work well in many cases. 

Recommended crossover frequency table

Speaker/System TypeCrossover Freq. & TypeNotes
Subwoofers 70-80 Hz (low pass)

Good low-pass frequency range for subwoofer bass & blocking midrange sounds. Best for pure, clear bass sound that "hits."

Car main (full range) speakers 56-60Hz (high pass)

Blocks low-end bass that causes distortion or speakers to "bottom out." Great compromise between full-range sound and midrange bass capability.

Tweeters or 2-way speakers 3-3.5KHz (high pass, or high/low-pass)

Most 2-way or 1-way (tweeter) crossovers use a frequency near this as most tweeters can't handle sounds below this range. Same for woofers above this range.

Midrange/woofer 1K-3.5KHz (low pass)

Woofers and many midrange speakers do not perform well above this general range. They're poor for treble and a tweeter should be added.

3-way system 500Hz & 3.5KHz (Woofer/tweeter crossover points)

Similar to 2-way systems the upper freq. would be the same. Midrange drivers in a 3-way system often do not perform well below 500Hz or 250Hz in many cases.

How to set the crossover frequency for speakers on your amp

How to set crossover frequency on car amp diagram

How to set high pass filter options on your amp (for main speakers)

Most people typically use a car amplifier for one of a few basic systems:

  1. Driving front and rear full range speakers, no subwoofer
  2. Driving front and rear full range speakers plus a subwoofer
  3. Driving a subwoofer

For cases #1 and 2, if your amplifier has a built-in crossover option you can use the high pass crossover to block low end bass that small speakers simply can’t produce well, if at all. The end result is that you’ll be able to drive your main speakers with more volume and lower distortion.

We only want to block that certain range of bass that subwoofers can handle. We don’t want to block bass found in the lower end of midrange like from the vocals in music (for example, around 100-120Hz or so). 60 to 70Hz or so are pretty common crossover frequencies that usually work well.

Adjusting an amp’s high pass crossover

For amplifiers with adjustable crossovers, use the following steps:

  • Turn off equalizer or bass boost functions
  • Set the front channel or front and rear (if using both) crossover switches to “HP” or however they’re labeled for the high pass function.
  • Adjust the crossover frequency control to the lowest setting (this is usually around 50Hz for most amps).
  • Using a small screwdriver, turn it up slightly – about 1/8 of a turn. This should be around the 60-70Hz range.
Note: Not all amplifiers offer an adjustable control. Some (especially ultra-compact models) use fixed frequencies and switches only. In that case, try using the switch position closest to the 60-70Hz high pass frequency range.

How to set subwoofer crossover frequency options

Similarly, do the following to adjust the subwoofer frequency & crossover:

  • Turn off equalizer or bass boost functions
  • Set the crossover switch to “LP” or however it’s labeled for the low pass
  • Adjust the crossover frequency control to the lowest setting (this is usually around 50Hz for most amps).
  • Using a small screwdriver, turn it up slightly – about 1/8 of a turn. This should be around the 70Hz range
  • Adjust as needed: if you’re not happy with the low-end range (the range of bass sound produced), don’t be afraid to adjust the frequency control a bit.
TIP: With decent power and a good speaker enclosure properly matched to the sub, you should have clean, pure bass at this point.

However, I’ve seen many cases where a subwoofer installed in the wrong type of subwoofer enclosure produces bland, poor sound. A crossover can’t fix that problem.

What crossover slope do I need? Does it make a difference?

What crossover slope do you need image of man thinking

In some cases, you’ll be able to choose from a number of crossover slopes (the steepness of the cutoff) on your amplifier or other components. As I mentioned earlier, the slope how effective a crossover is at allowing fewer unwanted sounds to reach your speakers, with higher numbers being more effective.

And as I mentioned ealier, -12dB per octave (“-12dB/octave”) is very common in car audio. While it may seem like the rule of “more is better” applies here, the truth is that most of the time a 12dB or 18dB/octave crossover slope is all you’ll need.

Why do some electronics offer more crossover slopes?

Some amps, head units, and digital processors/equalizers for car audio offer more crossover options for people who want advanced control – especially if you’re working on a high-end sound system. For example, when bi-amping speakers (using an electronic crossover and separate amp channels for the tweeter, the midrange speaker, and so on), you can take advantage of each speaker’s natural behavior and get super-detailed control over the signals you send to them.

That’s a much more advanced topic and worth its own article, by the way.

However here are the basic rules for crossover slopes that will work for 90% of people:

  • A 12/dB setting is good and will do the job in most cases for subwoofers (low-pass) and full-range speakers (high-pass).
  • However, 18dB/octave can be better for some subwoofers depending on your particular subwoofer, the enclosure, and how your vehicle alters the sound. In that case, experiment using the -18dB setting and see how it sounds.
  • 6dB/octave is a bit poor and will allow sounds to pass that can “muddy” the sound and just isn’t good enough for bass speakers. I don’t recommend that in most cases.

Most of the time, the main goal is to have the same cutoff at the same frequency. The goal, in perfect conditions, is that the speakers match up just right so there’s not much overlap in their sound as well as no gaps in the sound.

However, it’s definitely a lot harder in the real world. In my experience, however, 12dB/octave works well and is effective enough to make a big difference in how your system sounds.

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What Is A Crossover Frequency? What Does A Crossover Do? A Helpful Guide

What does a crossover do? What is a crossover frequency? Featured image

Wondering what crossovers do and what a crossover frequency is? Trust me, I know – it can be a bit confusing at first.

Crossovers are incredibly important for a great-sounding stereo system whether in your home, car or nearly anywhere that speakers and an amplifier are used.

In this detailed post, I’ll explain what they are, how they work, and much, much more in a way that anyone can understand.  

Contents

Infographic – Audio crossover facts

What does a crossover do infographic diagram

What is a crossover frequency? What does a crossover do?

Crossover frequency and crossover basics summarized
  • Crossovers are used to separate an incoming musical signal into 1 or more outputs. They offer a way to “cut off” certain sound ranges to send the best range to each type of speaker (For example, tweeters and woofers in a 2-way speaker system)
  • A crossover works using the principle of electronic filters to filter out (block) a range of musical sound frequencies as desired.
  • A crossover frequency is the sound frequency that starts the cutoff point for crossover filters. It’s the frequency point at which signals are reduced by 3 decibels (represented as -3dB)
  • A crossover’s outputs are the signal ranges allowed to pass such as high-pass (lower frequencies are blocked) and low-pass (higher frequencies are blocked)
  • There are 2 types of crossovers: active (electronic) and passive (speaker) types. Both types are very commonly found in home, car stereo, and professional audio systems

When we think about musical signals we don’t always realize the important things going on behind the scenes. In fact, you’ll almost never find a good-sounding speaker system that isn’t using 1 or more types of crossovers.

That’s how important they are!

A crossover (audio crossover) is an electrical or electronic assembly that separates a musical sound source and provides outputs best suited for certain types of speakers.

There are 2 types of crossovers:

  • Active (electronic) crossovers
  • Passive (speaker) crossovers

Crossover frequencies explained

Shown: One of the most common crossovers used directly on speakers and the crossover frequency as a real-world example. As tweeters can’t produce bass sounds, they distort and can even be damaged by heavy bass. Using a crossover, therefore, makes it possible to block (filter out) unwanted sounds below the crossover frequency. (Shown is a typical frequency used at 3,500 Hz [3.5 KiloHertz]).

The crossover frequency is the sound frequency point at which sounds after that will be greatly reduced, effectively blocking them.

We use it as a reference point at which the output to a speaker (or the input to an amplifier, when using active crossovers) is reduced by 3 decibels (-3dB). Normally the crossover frequency is used as a starting point in mathematical computations for crossover design.

In the world of electronics, it’s also sometimes called the corner frequency or cutoff frequency.

What’s the simple answer?

All sound frequencies after the crossover frequency are cut more and more past it, with an increasingly steep reduction – to the point where they’re almost completely blocked.

In other words, a crossover filters out a range of sound you’d like to prevent reaching speakers, starting at the crossover frequency.

What does sound “frequency” mean?

Diagram explaining sound frequency definitionIn this simple diagram, you can see what I mean by “frequency.” After all, the word simply means “how many times something happens.” Likewise, sound frequencies are assigned a number by the number of times they occur per second.

When we talk about “frequency” we’re referring to a number range for the human ear. For math & engineering purposes most of the time we use the range of 20 to 20,000 Hertz (20 to 20 KiloHertz, or 20 thousand Hertz).

In reality, the human ear can only hear down to around 30 Hz and near 16 KiloHertz, although it depends on your ears.

Hertz is a label used to represent frequency in terms of cycles per second. It’s because all sound waves (and electronic audio signals too) are alternating waves that happen many times per second.

“Hz”, “KiloHertz”, “kHz” are shorter ways of writing it (Kilo = the thousands marker, as you might recall from math class).

As an example, here are some of the most common sound frequencies that crossovers help with:

  • Bass: 20-100Hz or so
  • Midrange: (vocals, instruments, and more) ~100Hz to around 3Khz
  • Treble: (high-frequency sounds) Around 3KHz to 20Khz

How does a crossover work? What is a speaker crossover?

As I mentioned earlier, there are 2 kinds of crossovers. That’s true even if they’re built into an amplifier or speaker cabinet itself. The same basic designs are used just in a different package.

1. Active (electronic) crossovers

Illustrated diagram of an electronic (active) crossover example

A typical example of a separate electronic (“active”) crossover. In this example of a separate crossover used with car stereo amplifiers (nearly identical to those used in home stereos, too) you can see the RCA jack audio inputs and the crossover’s adjustable/switchable outputs. One set of output jacks provides a high-pass signal to connect to an amp for driving tweeters or full-range speakers while blocking bass. The 2nd output is for providing a bass-only signal to the amp for woofers.

Illustrated view of a car amplifier built-in crossover and componentsA typical car amplifier’s built-in electronic crossover circuitry illustrated. Sometimes called the “front end”, an amplifier’s internal crossover section is made up of a few basic electronic parts: Variable resistors, operational amplifier chips, capacitors, and fixed value resistors. They’re designed just like separate crossovers to give adjustable features & variable crossover frequency settings.

Electronic crossovers are also sometimes called “active” crossovers as unlike speaker crossovers, they need a power supply connection to work. Also, unlike speaker crossovers, they’re used before an amplifier.

While speaker crossovers connect directly to the higher-power output terminals of an amp and then to speakers, electronic crossovers work only with small signals. They’re connected to the outputs of a stereo in most cases.

How electronic crossovers work

Image showing a typical op amp IC and low pass crossover circuit example

Left: A typical operational amplifier (Op amp) integrated circuit (IC), the Texas Instruments TL072. Right: An example of a low-pass crossover circuit using an op-amp to filter out high-frequency sounds.

Electronic crossovers may sound very complicated (and they are, at least in some ways) but they’re actually based on pretty basic principles.

They work using a variety of electronic filter circuits based around a very common electronic component: the operational amplifier (“op amp”). Op amps are tiny multi-purpose amplifiers that are very useful for amplifying or changing an input signal in many ways.

They, together with resistors and capacitors, can be used to control how a music signal is output and will block certain ranges of frequencies.

Alpine car amp electronic crossover schematic exmaple

A schematic of a typical electronic crossover. In this case, the left stereo channel of an Alpine car amplifier’s built-in crossover circuitry is shown.

Electronic crossover functional diagram showing the basic blocks of operation

When put together in a way in which you can select your preferred filter (high or low pass, for example) and adjust the crossover frequency they form a complete crossover unit.

Basically, they offer several adjustable filters so you can prevent a range of musical frequencies from going to the wrong speakers. The crossover frequency is usually adjustable using switches or dials to allow you to change it as you like.

Once an input signal is applied, you’ll get the following outputs (depending on the type, as there are many options available):

  • High-pass outputs to block bass from tweeters or to block low-end bass from main speakers. This allows more volume without distortion as small speakers can’t handle heavy bass well.
  • Low-pass outputs for bass: When used, this blocks the vocals and other higher frequency sounds that woofers and subwoofers can’t reproduce well. The result is good, clear, heavy-hitting bass.

2. Speaker (passive) crossovers

Home and car stereo speaker crossover examples illustrated and labeled

Top: A typical car stereo speaker crossover, with the main parts labeled. Bottom: A typical home stereo speaker crossover, which is extremely similar. (These are normally installed inside the speaker cabinet) Both use capacitors and inductors to form crossover filters and control the sound sent to tweeters, midrange speakers, or woofers for best audio sound quality.

Speaker crossovers are sometimes called “passive” crossovers as they don’t need an external power supply connection. They work using passive components: capacitors and inductors.

A speaker crossover is an electrical circuit that uses inductors and capacitors to filter a speaker signal and split it among 1 or more outputs. The outputs depend upon the frequency response of the speakers used.

Unlike electronic crossovers, normally they’re connected to the outputs of an amplifier and then to the speakers you’d like to use.

2 way speaker system and crossover diagram

One of the most common speaker crossover types in use today: A 2nd-order 2-way speaker crossover with tweeter and midrange/woofer outputs. Inductors are represented with an “L” symbol and capacitors with a “C” symbol. A “2nd order” crossover just means that the second stage of parts is used to make the crossover filter out the unwanted frequencies even more effectively.

Capacitors and inductors have some interesting properties depending upon the frequency of a signal applied to them:

  • Capacitors have more “resistance” (called impedance, in this case) to a low-frequency signal than a higher one. The lower the frequency, the less signal that is allowed to pass.
  • Inductors are coils of wire that have more resistance to a high-frequency signal than a lower one. Therefore they filter out higher sound frequencies.

This works because when a capacitor or inductor has a signal applied to it that’s past the crossover frequency (depending on how it’s used), the resistance increases, which reduces the speaker voltage.

This means the speaker will receive less and less of the speaker signal that we want to block.

In all cases, the part value is chosen according to the speaker “Ohms” (impedance rating) it’s planned to be used with. That’s super important!

Note: Speaker crossovers can only be used with the speaker impedance they’re designed for, or they won’t sound the same.

For example, using an 8 Ohm home speaker crossover with a 4 Ohm car speaker won’t work correctly. That’s because the part values were chosen for one impedance only. When you change that, it dramatically changes the crossover frequency!

Image of a tweeter used with inline bass blocker capacitor speaker crossover example diagramWhen used in series with a tweeter, a crossover blocks damaging and distorting bass that tweeters can’t handle. Capacitors like in this example can be used as a simple speaker crossover for tweeters.

Speaker crossovers are designed in many ways but all have the same basic design structure – only the details change.

They’re also often labeled with names like “1st order”, -6dB/octave, “2nd order”, -12dB/octave, and so on. I’ll explain a bit more about that as we go.

For now, you only really need to know that 2nd order and 3rd order crossovers are the same thing but with more crossover stages, or “orders”, added to make the filtering ability even more effective.

What are decibels and why do we use them for audio?

Diagram showing the formula for crossover voltage in decibels with example math problem solved

Crossovers (and a lot of other audio electronics & equipment) are measured using Decibels. Decibels (“dB”) are a convenient mathematical way of dealing with numbers that occur as powers of 10, unlike linear numbers, which occur in a straight line. Shown is an example of figuring out the reduction, in dB, of a crossover output.

In the real world, lots of measurements deal with things that don’t increase or decrease in a straight line (“linear”) but instead on a curve (“non-linear”, or logarithms).

I won’t bore you with heavy math here, but we use Decibels in the world of audio as a mathematical way of dealing with musical electrical signals. That’s because a lot of it happens not in a straight line but in curves.

That is, much of the audio world works with powers of 10 (logarithms, which you might remember from your algebra class). Hence the need for a way to deal with those – that’s where the dB representation comes in handy.

And it’s not just crossovers that work with decibels but even your own ears are “logarithmic”! That is, the volume your ears perceive is measured in dB, too.

What is a crossover “slope”?

Crossover slope diagram and examples illustrated

Diagram showing the crossover slope, or cutoff steepness, for the most common crossover types. Crossovers have “orders” – that is, 2nd, 3rd, or more stages that increase their ability to filter out the unwanted sounds frequencies sent to a speaker.

A crossover slope is the steepness of a crossover’s filtering ability. In other words, it’s how much a crossover’s blocking (filtering) ability is past the crossover frequency point.

Slopes, just like the crossover frequency, are determined according to a level in decibels (dB). The negative symbol is used to show they represent an attenuation, or reduction, of the signal. (Which of course is how crossovers work!)

As you might have guessed, the larger the steepness (greater the slope), the more effective the crossover is at filtering out bass sent to a tweeter, as an example. Likewise for other speakers connected to it.

In the audio world, we commonly refer to frequencies in octavesAn octave is a doubling or halving of a frequency number.

For example, when we refer to a crossover having a cutoff of -6dB per octave, we mean it will continue to cut the input signal more by a factor of 6dB for every doubling of the previous frequency.

Like this: (Low pass crossover frequency) -6dB @ 1KHz, -12dB @ 2KHz, -18dB @ 4KHz, -24dB @ 8KHz, –32dB @ 16KHz, up to 20KHz.

What are the most common and best crossover slopes?

12dB per octave speaker crossover example image

There’s a lot more to say here, but crossovers are designed to be a good compromised between complexity, price, and sound quality. While you might think “the higher order, the better” would always apply, things get much more complicated once you get past 3rd or 4th order crossovers.

Generally speaking, a -12dB crossover slope is one of the best compromises and works well for most speaker systems used today.

One reason is that it’s simple. has fewer design complications, but still gives a good cutoff ability that works great both for single speakers or 2-way speakers.

In general, the most commonly used are:

  • -6dB
  • -12dB (the most popular, by far)
  • -18dB

Electronic and 2-way speaker crossovers are nearly always -12dB models.

What is a two way speaker?

Image showing diagram with home and car stereo 2-way speaker examples

Examples of very common 2-way speakers you’ll find in either car or home stereos (in addition to other types as well). They have nearly the same things in common except that home stereo speakers are usually placed in a speaker box (speaker cabinet/enclosure) while car speakers may be installed separately in many cases. Both use a 2-way crossover to produce a very nice sound.

What are 2 way speakers?
  • 2-way speakers are a speaker system in which 2 speakers work together to produce the full range of sound. Audio from a stereo amplifier is divided between the speakers by a 2-way speaker crossover.
  • 2-way speakers are the most common type in the world, and many offer low-cost with great sound
  • These types of speakers use a tweeter for high frequencies and a woofer speaker for the midrange and bass portions of the music.
  • While the type of crossover varies from model to model, one of the most common and best-performing is the 2nd order crossover with a slope of -12dB per octave.

2-way speakers use 2 speakers on each channel and a crossover to divide the audio frequencies reproduced between the two. Each speaker receives a signal range it’s best suited for.

Illustrated diagram showing examples of 2 way home and car stereo speakers with 2 way crossovers

For example in 2-way speaker design:

  • Tweeters receive only high frequencies – typically around 3.5KHz and above
  • Woofers only receive lower frequencies – typically around 3.5KHz and below

The crossover frequency used varies by design needs, to there’s no “one” crossover frequency that works in all cases. Additionally, crossovers must be matched to the right impedance (Ohms rating) for the speakers they’re designed to work with.

The 2-way crossover evenly splits the incoming sound and sends it to the correct speaker such as the tweeter and a woofer.

Image of coaxial 2 way car speaker example

Coaxial speakers are 2-way speakers, too. In fact, in the example shown here, you can see crossovers on the rear of the speaker. Just like separate crossovers, lower frequencies are directed to the large woofer and highs are sent to the tweeter.

The result is that the sound produced is a full range of sound, but without distortion or poor performance you’d get when trying to play the same range in only 1 speaker. In other words, a 2-way speaker design can produce a clean, detailed sound.

In many systems, you won’t necessarily need expensive components or speakers to get great sound. Even low-cost 2-way speakers can sound very nice!

What is a good crossover frequency? What crossover frequency should I use?

The truth is, there’s no good set of crossover frequencies that work for every speaker. It depends on a lot of things.

However, here are some of the most common frequencies that work well in many cases. This is based on my experience with speaker design and many stereo installations.

Recommended crossover frequency table

Speaker/System TypeCrossover Freq. & TypeNotes
Subwoofers 70-80 Hz (low pass)

Good low-pass frequency range for subwoofer bass & blocking midrange sounds. Best for pure, clear bass sound that "hits."

Car main (full range) speakers 56-60Hz (high pass)

Blocks low-end bass that causes distortion or speakers to "bottom out." Great compromise between full-range sound and midrange bass capability.

Tweeters or 2-way speakers 3-3.5KHz (high pass, or high/low-pass)

Most 2-way or 1-way (tweeter) crossovers use a frequency near this as most tweeters can't handle sounds below this range. Same for woofers above this range.

Midrange/woofer 1K-3.5KHz (low pass)

Woofers and many midrange speakers do not perform well above this general range. They're poor for treble and a tweeter should be added.

3-way system 500Hz & 3.5KHz (Woofer/tweeter crossover points)

Similar to 2-way systems the upper freq. would be the same. Midrange drivers in a 3-way system often do not perform well below 500Hz or 250Hz in many cases.

Recommended reading

Product image of the Loudspeaker Design Cookbook by Vance Dickason

Want to learn a lot more and truly understand speakers, crossovers, and how to design a great sounding system of your own? Here’s the very book I learned a lot from myself.

You can pick up your own copy of the famous Loudspeaker Design Cookbook at Amazon today. It’s an excellent source of information including formulas you too can use to build your own car or home loudspeaker projects.

Interested in learning more about what tweeters do and the different kinds? Check out my wonderful guide to tweeters here.

For some great articles about crossovers, speakers, and lots of DIY projects, check out the Elliot Sound Products page.

Did I leave anything out? Drop a note!

I hope you’ve found my post helpful, clear, informative, and most of all what you were looking for. If you’ve still got questions, suggestions, or just want to say hi, leave a comment below or send me a message from my contact page.