Crossovers are an integral part of any stereo or home theatre system that sounds great. Unfortunately, understanding how they work and accurately setting crossover frequency for various speakers can be confusing. The crossover frequency of your subwoofer is the frequency at which your speakers start to roll off, and your subwoofer kicks in with LFEs and bass notes. Most modern AV receivers feature an auto EQ program that automatically assigns the proper crossover frequency based on your loudspeakers’ capabilities. It’s generally best to leave these settings where they are.
What Is a Crossover Frequency?
A crossover is an electronic or electrical system designed to split the sounds from a musical source and provide the best output for a specific speaker. Most speaker systems that sound great come with at least one type of crossover built-in.
On the other hand, crossover frequency refers to the sound frequency point, after which specific sounds will be reduced or effectively blocked. The crossover frequency is used as the reference point at which a speaker’s output—or input to an amplifier—is cut by 3 decibels (-3dB)
What Are Decibels?
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 happen 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 to deal with those – that’s where the dB representation comes in handy. It’s not just crossovers that work with decibels, but even your ears are “logarithmic”! That is, the volume your ears perceive is measured in dB, too.
The Different Types of Crossover Frequencies
The following are the different types of crossover frequencies you should know about:
With an active crossover, each sound driver gets its own channel amplification. Giving the subwoofer, woofer, and tweeter their channels, the available power and dynamic range is significantly increased from softest to loudest. This gives you better control of the whole audio spectrum as well as your system’s tonal response.
An active crossover is typically wired between the receiver and amplifier, cutting out any unnecessary frequencies and ensuring that the amp doesn’t waste energy on boosting them. This ensures that the amp can focus solely on delivering the frequencies you’d like to hear from a specific speaker.
Active crossovers also come with volume controls on the channels, allowing you to maintain the sound balance from all the drivers. Some designs of active crossovers come with other sound-processing features like equalization, allowing you to tweak further the sound generated until you are satisfied.
However, the downside to active crossovers is that they require +12V, ground, and turn-on connections to run. This makes them more challenging to install and set up.
If you can spare a little time, however, you should be able to deal with this challenge. The advantages far outweigh the setup difficulty, which is why most people that take their music seriously go for systems that have active crossovers. It is the perfect way to keep your speakers belting out crisp and clear sounds of all frequencies.
Passive crossovers don’t need a connection to a power source to work. There are two variants of these types of crossovers: in-line crossovers and component crossovers. The latter sits in the middle of the amplifier and the speakers, while the former fits between the amp and the receiver.
Passive Component Crossovers
These crossovers fit into the signal path beyond the amplifier. They feature a small network of capacitors and coils and are installed near the speakers. Speaker systems with component crossovers are designed to deliver the best performance possible out of the box with little or no external tweaks. They are also simple to install and set up.
A full-range signal first leaves the amplifier with a passive component crossover, and then it gets to the crossover, where the signal is separated into two parts.
The high notes are sent to the tweeter, while the mid and low notes go to the woofer. In most passive component crossover systems, you can reduce the tweeter sound a bit when you think it is too loud for the woofer.
A passive component crossover will waste power because it is filtering a signal that has been amplified already. The unwanted sounds are released as heat.
Additionally, you need to consider that speakers don’t maintain fixed impedance as they play sounds. This can change the crossover point or frequency response of a passive component crossover. This can cause some inconsistencies with the sound definition.
While component crossovers operate on speaker-level signals mostly, in-line crossovers connect before the amplifier. These crossovers have a cylindrical appearance, with RCA connectors at both ends. They plug directly into your amplifier’s inputs.
In-line crossovers solve the problem of energy wastage where the amplifier processes signal you won’t need. This means you don’t have to worry about scenarios like high frequencies being processed by a subwoofer amp.
By installing an in-line crossover system, you can improve the sounds of your system a great deal, especially if you have a component speaker system.
However, you should know that in-line crossovers generally come set to a specific frequency and can’t be adjusted. Additionally, in-line crossovers interact differently with different amplifiers. This means that the crossover points can be unpredictably affected.
How to Determine Speaker Crossover Frequency
You’ve seen some recommended ranges to work with for your speaker crossover. To determine the speaker’s crossover frequency, you, first of all, need to understand the type of speaker you are dealing with. You can apply the recommended crossover frequencies to them if you can distinguish between 2-way and 3-way speakers or woofers and subwoofers. For a more specific setting, however, here’s what you should do:
1. Look at your speaker’s specification sheet only to find the details for the frequency response. It will look like “32-10,000Hz” or other numbers within that range.
2. Go to your receiver’s setup menu with the remote to find the part of the menu that highlights the size of your speaker and crossover point. The process of finding this menu will vary from one product to the other, so you may have to use your product manual.
3. While in the receiver’s menu, look at the speaker’s specification sheet, and take note of the lowest frequency. In most 2/3-way speakers, it will be 30, 40, or 55 Hz, but on subwoofers, it could be as low as 20 Hz.
4. Pay attention to the options that are available in your receiver’s crossover adjustment menu. Now, multiply the lowest value on your speaker’s specification sheet by two. This means that if the value is 30 Hz, the crossover point in your receiver’s menu should be 80 Hz. This is expected with a standard 12db/octave high-pass crossover found in most receivers.
5. The high-pass crossover point is the frequency at which your bookshelf speaker gives way to the subwoofer (assuming you have such a configuration, for example). The low-pass crossover point is the range where the subwoofer will begin to taper off to avoid playing a lot of mid-range sounds.
6. The result of this is that there’ll be a flat response from the crossover point down to when the speakers naturally start to roll off. The “roll-off” point is typically below the speaker’s designated lowest frequency, at which point it will stop producing any sound. This means that a speaker with the lowest frequency rating of 40 Hz will have its roll-off around 32 Hz.
What Is a Crossover Slope?
A crossover slope refers to the depth of a crossover’s filtering capacity. It’s basically how steep a crossover’s filtering can go beyond the crossover frequency boundary. As is the case with a crossover frequency, slopes are also determined in decibels. With crossover slopes, bigger is better. A larger steepness or greater slope means that the crossover effectively filters out a specific sound frequency before sending it out from a speaker system.
What Is a Good Crossover Frequency?
A good crossover frequency is a range at which the crossover can filter the unwanted sounds perfectly. It’s hard to settle on a unified crossover frequency for every speaker because many factors come into play when setting one. However, there are typical frequency ranges that will work well in many cases.
The recommended crossover frequency is 80 Hz (low pass). This an excellent low-pass frequency that ensures the subwoofer bass is prioritized without including any midrange sounds. It is best for low-end bass.
The recommended crossover frequency is 56-60 Hz (high pass). At this frequency, low-end bass, which can cause distortion, is filtered out. This crossover is the perfect middle ground between midrange bass capability and full-range sounds.
For tweeters and 2-way speakers: the recommended crossover frequency is 3.5 kHz (high pass, or high/low pass). Anything below this range for these speakers will lead to suboptimal performances.
Mid-range speakers and woofers
The recommended crossover frequency is 1-3.5 kHz (low pass). Most woofers and midrange speakers don’t deliver quality sounds above this range. This is why they have to be augmented with tweeters to avoid poor treble delivery.
For 3-way speakers: the recommended crossover frequency is 500 Hz and 3.5 kHz. The midrange drivers in a 3-way system most likely won’t deliver quality sounds below 500 Hz or 250 Hz.
A Crucial Detail To Remember
To set crossover frequency for speakers, you need to know the exact speaker type first. If you know the kind of speaker you have, you can then work with its recommended crossover range. For subwoofers, for example, the recommended crossover frequency is 80 Hz.
1. If you know your speaker’s frequency range, set the crossover point roughly 10 Hz above the lowest frequency, your speakers can handle cleanly.
2. The most common crossover frequency recommended (and the THX standard) is 80 Hz.
3. The numbers below highlight general guidelines for speaker/subwoofer crossover frequencies:
- On-wall or Tiny ‘satellite’ speakers: 150-200 Hz.
- Small center, surround, bookshelf: 100-120 Hz
- Mid-size center, surround, bookshelf: 80-100 Hz
- Large center, surround, and bookshelf: 60-80 Hz
- Extensive center, surround bookshelf: 40-60 Hz.
- Tower speakers with 4”-6” woofers: 60 Hz.
- Tower speakers with 8”-10” woofers: 40 Hz or Large/Full-Band (i.e., full-range).
4. Listen for a smooth transition between speakers and subwoofer. Ideally, the blending will be so seamless, you won’t be able to localize the bass, and everything will play in unison.
5. If you’re noticing a bass bump at the crossover frequency, try adjusting the volume control to match the output of your main speakers.
Setting The Phase and Crossover
How to Set the Phase
The first thing you need to do at this point is to set all your speakers so that they’ll be facing the exact directions. With this approach, you can better judge the quality of the sound. You may end up with subwoofers that are not in sync with each other phase-wise. When this happens, the bass quality of each speaker will end up cancelling each other out, causing poor quality sound overall.
If you have RCA cords on your speakers, you can’t switch the wires. In this situation, the best thing to do is to set up a phase switch. You can do this by setting up your speakers so that you can still listen to them without fully installing them in the entertainment case or the wall. Once you’ve done this, listen to the quality of the sound. If you are not impressed with the bass, you can turn the phase to 0 or 180 to get the grade you are looking for.
How to Set the Crossover
As you’ve seen above, failing to set the crossover frequency means that the subwoofer may not be able to focus on delivering low-frequency notes or deep bass solely. If you bought an integrated system with an EQ feature, the crossover might have been set automatically on your subwoofer and the rest of your speakers. If this isn’t the case for you, you can select the crossover manually. Here’s how to do it:
1. Find the low-end of the subwoofer’s frequency range from your user manual or the manufacturer’s website.
2. Set the crossover point 10 Hz higher than this range for the best result (or go with the recommended 80 Hz).
3. Listen for a smooth transition between your subwoofer and the rest of the speakers ensuring that the sound is crisp.
4. If you hear a bass bump at the crossover frequency, adjust the subwoofer volume to closely match the other speakers’ sound in your lineup.
Some Outboard Crossovers You May Want To Look Into
Planet Audio EC20B 3-Way
The Planet Audio EC20B 3-Way crossover offers three filter circuits for a wide range of setup options. Its variable low-pass range is 32 Hz to 250 Hz, while the high-pass range is 40 Hz to 400 Hz. It also has a bass generator with a frequency response of 10 Hz to 20 kHz. Additionally, it manages to match the other speakers’ sound in your lineup closely through the independent front, rear level, and subwoofer controls.
Behringer Super-X Pro CX2310
The Behringer Super-X Pro CX2310 is a professional stereo 2-way/mono 3-way crossover famous for its Linkwitz-Riley filters and 24dB/octave. It provides a flat summed amplitude response, which ensures zero phase difference. There’s also an additional subwoofer output with independent frequency control. The individual output gain controls and mute switches give you more flexibility with setting up your system.
The XV-6-V15 6-Way offers a continuously variable crossover frequency with separate inputs for your speakers and subwoofers. It comes with a multiplier switch and delivers non-fade low pass output and front and rear high pass outputs. The bass boost feature will also help deliver seamless and air-tight bass from your subwoofer.
The SoundStorm SX310 is a feature-packed crossover. It has a parallel input system and a selectable crossover slope. The bass boost function allows you to tune the center frequency to deliver the most complex bass with little to no distortion. Is your subwoofer’s position causing cancellation as a result of overlapping sound waves? The Sound Storm SX310’s phase shift selector is designed to deal with all “out of phase” issues. With the system’s independent channel output level controls, you can quickly improve your sound setup’s spatiality. The three-year warranty offered by the brand is one of the most generous in the industry.
Crossover frequencies may sound like it should be left to the experts but they are an often integral part of the speaker sound reproduction. For audiophiles who wish for that last improvement in sound and a better control with which their music is delivered, crossover frequencies should be highly considered. They help to filter out unwanted frequencies and in doing so promote optimal delivery of sound output from speakers. While some speakers have some built-in crossovers, having an additional layer of control can also help fine tune your personal preferences and also unlock your speakers true potential.
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