Stereo Crossover
- A 2-way crossover will split the sound between two drivers, while a 3-way crossover enables 3 drivers to work in conjunction. One of the most appealing features of an active crossover is the ability to adjust the crossover frequencies, and many models also allow you to adjust the slope as well.
- A speaker crossover is a technology used in audio production to optimize speaker system performance by sending each speaker only the frequencies it is designed to accurately reproduce.
The crossoverdesign can make or break any multi-way loudspeaker. Having the world’s best drivers with a poorcrossover design will yield poor results. It is important to approach crossoverdesign with humility because it truly is an art that requires experience toperfect. Yes, it is possible to get decentsound by sending driver data sheets off for a generic crossover design. However, without proper analysis of thedrivers in the intended cabinet it is a game of roulette. This design overview neglects many designconsiderations a professional designer may consider such as time alignment,distortion and polar response but provides a starting point.
Before designing acrossover, the cabinet must be fully assembled including ports anddrivers. I typically run a separatespeaker wire from each driver out of the port and label each wire. For sealed loudspeakers, connect the wooferto the binding post as this is the first driver measured in the cabinet. Using SoundEasy, each driver is measured inthe cabinet to obtain frequency response and electrical impedance. These parameters are obtained following thetest methodology outlined in our LoudspeakerMeasurement Standard. Pleasenote that any measurements taken near field must factor in the effects ofbaffle diffraction. SoundEasy allowsmodeling and application of baffle diffraction estimates to any frequencyresponse data. Getting good measurementdata is one of the hardest parts of loudspeaker design. It is crucial to validate your results bytaking measurements using both near field and quasi-anechoic gated techniquesand compare the measurements before proceeding. The measurement data is subsequently used in SoundEasy’s crossoverdesign tool.
For the mid/woofer crossover there are 4 octaves between 200-3.2k Hz, 200-400-800-1600-3200. 800 Hz is the middle frequency, with 2 octaves flat in either direction. For the tweeter/mid crossover, there are only 1 octaves, 2000-4000. 3k Hz is the crossover point with 1/2 octave stable in either direction.
DIY Crossover Installed in Cabinet
Although CAD hascome a long way, designing a loudspeaker crossover benefits from somebackground in electronics. SoundEasy has2-way to 5-way crossover templates covering 1st order to 4thorder crossover topologies. Additionally, there are templates for a wide array of typical filtersand compensation circuits. The CADframework allows implementation of any circuit or filter topology imaginable solong as it uses inductors, resistors, capacitors, operational amplifiers,potentiometers or logic gates. If youhave not ever studied filter design or do not know what the previously-mentionedelements are, you may want to consider studying up to improve your chances ofpulling off a working and affordable solution.
Stereo Crossover Definition
The first step Itake when designing a crossover in SoundEasy is to determine workable crossoverfrequencies and filter orders. Thisrequires careful inspection of the driver data sheets, frequency responsemeasurement and driver impedance. It isimperative to make sure that response anomalies, such as the breakup of a metalcone driver, are sufficiently attenuated by the crossover so that they are notaudible. It is generally a good idea tokeep the crossover frequencies low enough to prevent driver beaming but highenough to prevent driver failure. Forexample, crossing over most tweeters below 1.5kHz is a bad idea if it is meantto play program material at 110dB or has a resonant frequency above 750Hz. Crossing an 8 inch bass driver at 5kHz willresult in poor dispersion and transient response at higher frequencies. As a rule of thumb, the max frequency for agiven driver diameter can be equated by taking 13560 and dividing it by thedrivers effective diameter. For an 8”driver with an effective cone diameter of 7”, this means that the maximumcrossover frequency should not exceed 1937Hz.
A 4thorder crossover rolls off frequencies at 24dB per octave where as a 1storder crossover rolls off frequencies at 6dB per octave. Lower order crossovers have less phase shiftbut tradeoff power handling and masking out of band response anomalies. The designer has to determine the best set oftradeoffs for an intended design goal. SoundEasy has built-in filter templates for delay networks if a designerdesires to design a time aligned loudspeaker for higher order filters. It is also important to note that the filterorder does not have to match for each driver in a system but it does simplifythe design.
Once approximatecrossover frequencies and filter orders are determined, a filter can be developedin CAD. For the purposes of this designanalysis, a 2nd order crossover was designed which approximatelymatches a Butterworth filter target. Additional response shaping elements were added where needed to meet thedesign requirements. This circuit wasdetermined based on using a 2nd order low-pass for the woofer,band-pass for the midrange and high-pass for the tweeter. Due to the response anomalies and differencesin sensitivity, additional elements were added. The final circuit design is shown below.
Crossover Circuit inCAD
The componentvalues for the circuit design are determined using SoundEasy’s ingeniousoptimization technique. It is as simpleas setting a target response for a single driver and selecting the componentsSoundEasy should manipulate to attempt to meet the target response. In this example, a 2nd orderButterworth band-pass filter target was setup in the optimization dialog asshown in black in the figure below. SoundEasy will modify the selected crossover components and employ trialand error to arrive at the optimum component values required to meet thefrequency response target. Theoptimization technique will attempt thousands of combinations and may be runmultiple times to determine the best component values. While running optimization, it is important topay attention to the component values set by SoundEasy because it may setvalues that are very high inductances or capacitances and therefore expensive. This may take some playing around to getright. If you are unable to get close tothe target curve you might consider changing the filter topology. The midrange for the sample project tracksthe target curve pretty well but is not perfect at the high frequency knee dueto response problems with the driver itself. It is possible to shape the response further but more crossovercomponents equate to a more expensive crossover. It is easy to spend hundreds or eventhousands of dollars on crossover components. It is often better to solve extensive frequency response problems withbetter drivers or a more in-depth diffraction analysis.
Midrange CrossoverOptimization
The optimizationprocess is applied to the low-pass, band-pass and high-pass filters and acombined response is generated. Due toresponse issues, it may be necessary to attenuate a target or move thecrossover frequency slightly to obtain a flatter response. Ultimately, it may take several rounds ofmoving crossover frequencies and even filter orders to get to an acceptablesystem response. The combined systemresponse after optimization for this design is shown below.
3-Way CrossoverSummed Response
During the designprocess, it is important to pay close attention to system impedance graphs. It is no fun perfecting frequency when yourdesign has a minimum impedance of 1.5 Ohms. SoundEasy has an option to set the minimum acceptable impedance duringoptimization to help reduce the risk of developing a network that dips too lowfor the amplifier you are using.
As a final step,it is absolutely necessary to set the values of capacitors, resistors andinductors in the CAD editor to values you can actually purchase. This usually involves rounding up or down tovalues you can purchase. If thecrossover parts are expensive, you can attempt to reduce component values andsubsequently plot their effect on the final response. This is time consuming but can save you a tonof money. A 3-way crossover of thiscomplexity is not cheap. Using cheapelectrolytic capacitors this crossover costs close to $150 for componentsalone.
3-Way Crossover Billof Materials
Conclusion
Unfortunately, the tweeter used in this design did not measure close tothe data sheet at all and required pushing the crossover frequency up. Ultimately the dip at 4kHz is fixable but thecost required outweighs the benefit.
Personally, Iprefer loudspeakers that have a frequency response that tilts slightly downwardso I find the response of this speaker pleasing. It did not ultimately meet the design goal of+/-3dB frequency response deviation but it plays low bass with authority andsounds very good overall. Even though itis a ton of work, there is something very rewarding about designing aloudspeaker from the ground up and the owner of the speakers discussed in articleis extremely happy with his one of a kind creation.
DIY speaker Finished Product
Ultimately,designing your own loudspeaker is something you do because you like thecreative side of designing things. Ifyou are after bang for your buck sound, it is much cheaper and less time consumingto use someone else’s well-established and well-documented DIY design withpre-fabricated cabinets.
Some of mypersonal favorites include:
- http://www.linkwitzlab.com - Siegfried Linkwitz is a renowned loudspeaker designer that developsDIY loudspeaker projects for fun in his retirement. The new LX521 and older Orion loudspeakerprojects are considered by some to be among the best speakers available, evencommercially.
- http://www.troelsgravesen.dk - A Danish designer responsible for many well regarded mid to very highend DIY designs. Most require building acabinet but the designs represent very high value.
- http://zaphaudio.com - Although this site is notupdated much anymore, John Krutke has many good designs available as fullkits. He has also tested a slew ofdrivers if you need unbiased raw driver data.
- http://parts-express.com - Many full DIYkits and parts available directly from Parts Express
- http://madisound.com - Many full DIY kits andparts available directly from Madisound. They also offer a crossover design service using very good crossoverdesign software.
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.
To set crossover frequency for speakers, you need to know the exact speaker type first. If you know the type of speaker you have, you can then work with its recommended crossover range. For subwoofers, for example, the recommended crossover frequency is 80 Hz.
Read my article “Does Lower Hz Means More Bass? Bass & Frequency Link Explained” for some handy background knowledge which will help in understanding the subject better.
Also read my guide on Subwoofer Crossover Settings
The rest of the article will take a deep dive into crossover frequency and what it’s all about. Watch out for the recommended crossover frequency for other types of speakers apart from subwoofers.
What is Crossover Frequency
Stereo Crossover For Subwoofer
A crossover is an electronic or electrical system designed to split the sounds from a musical source and then providing the best output for a specific speaker. Most speaker systems that sound great come with at least one type of crossover built-in.
Crossover frequency, on the other hand, 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).
So, a crossover filters out the range of sound you’d like to prevent from reaching a certain speaker, but the filtering will only start at a specified crossover frequency.
What Are the Types of Crossovers?
Crossovers are divided into passive (speaker) and active (electronic) crossovers. With passive crossovers, you don’t need power to block sounds.
Active crossovers, on the other hand, require power, as well as ground connections, but they ensure you have better flexibility when it comes to controlling the finer details of your sound output. Below is a closer look at both of them.
1. Active Crossovers
With an active crossover, each sound driver gets its own channel amplification. By giving the subwoofer, woofer, and tweeter, their own channels, the available power, and dynamic range—from softest to loudest—is greatly increased. 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 further tweak the sound generated until you are satisfied.
The downside to active crossovers, however, 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.
2. Passive Crossovers
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.
3. 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.
With a passive component crossover, a full-range signal first leaves the amplifier, 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 the fact 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.
4. In-Line Crossovers
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.
You should know, however, 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.
Which Crossover Types Are the Best?
Now that you’ve seen all the possible crossover types, you are probably wondering which one of them to go with. Your decision should come down to just how seriously you’d like to take your sound setup. If you plan on regularly upgrading or expanding your system in the future, you won’t go wrong with a separate outboard crossover.
Relying on the crossovers that have been built into the amplifier and receiver isn’t a great idea in this scenario. This is because although they work well enough, you won’t have the same level of control that will be provided by an external or outboard unit.
Additionally, you won’t have to worry about losing the crossover after you upgrade your amp.
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 is very effective in filtering 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 is able to filter the unwanted sounds perfectly. It’s hard to settle on a unified crossover frequency for every speaker because a lot of factors come into play when setting one. However, there are common frequency ranges that will work well in many cases.
- For subwoofers: the recommended crossover frequency is 80 Hz (low pass). This a good low-pass frequency that ensures the subwoofer bass is prioritized without including any midrange sounds. It is best for low-end bass.
- For main speakers: 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.
- For midrange 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.
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.
If you can distinguish between 2-way and 3-way speakers, or woofers and subwoofers, you can apply the recommended crossover frequencies to them.
For a more specific setting, however, here’s what you should do.
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.
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.
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.
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.
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.
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 to produce any sound. This means that a speaker with the lowest frequency rating of 40 Hz will have its roll-off around 32 Hz.
How Can You Set the Phase and Crossover Frequency on a Subwoofer?
To set the phase and crossover frequency on a subwoofer, here’s what you have to do.
How to Set the Phase
The first thing you need to do at this point is to set all your speakers in a way that they’ll be facing the same directions. With this approach, you can better judge the quality of the sound.
It’s possible that you’ll 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 canceling 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 in a way 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 quality 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 solely focus on delivering low-frequency notes or deep bass.
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 set the crossover manually. Here’s how to do it:
- Find the low-end of the subwoofer’s frequency range either from your user manual or from the manufacturer’s website.
- Set the crossover point 10 Hz higher than this range for the best result (or go with the recommended 80 Hz).
- Listen for a smooth transition between your subwoofer and the rest of the speakers ensuring that the sound is crisp.
- If you hear a bass bump at the crossover frequency, adjust the subwoofer volume to match the sound from the other speakers in your lineup closely.
Some Examples of Outboard Crossovers You Can Buy
Some of the best outboard active crossovers you can find in the market today include:
Planet Audio EC20B 3-Way (Amazon link)
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 offers remote and independent front, rear level, and subwoofer controls.
Behringer Super-X Pro CX2310 (Amazon link)
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.
XV-6-V15 6-Way (Amazon link)
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, as well as front and rear high pass outputs. The bass boost feature will also help deliver seamless and air-tight bass from your subwoofer.
SoundStorm SX310 (Amazon link)
The SoundStorm SX310is 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 hardest 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 improve the spatiality of your sound setup easily. The three-year warranty offered by the brand is one of the most generous in the industry.
Should You Install a Crossover Frequency on Your Own?
If you have a perfect understanding of all the concepts that’s been discussed in this article, you can most certainly complete the installation of an external active crossover frequency. The user manual from any of the systems you purchase should guide you.
On the other hand, if it all sounds too technical for you, you are better off sticking with built-in crossovers or at least automatic variants. If an active crossover frequency can improve the quality of your sound setup, however, you should invite a professional sound engineer to complete the process for you.
Final Words
Crossover frequency sounds like technical stuff that should remain in the background. For most people, this is true. For audiophiles, however, every bit of improvement that can improve the overall sound counts.
What better way to improve the sound than ensuring that all your speakers are only delivering the exact frequencies they were made for? With the guide above, you can set crossover frequency for all the speakers in any audio system.
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