Ready to design and build your own speaker crossover? You’re in the right place!
Here’s a very easy-to-use speaker crossover calculator along with great info to help you.
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Contents
SPEAKER CROSSOVER CALCULATOR
You can use my speaker crossover calculator to generate parts values to build your own capacitor, experiment with different values, and more.
How to use the calculator
- Select the crossover type:
- 4 types are available: 2-way 2nd order Linkwitz-Riley (12dB/octave), high or low-pass 1st order Butterworth (6dB/octave), 1st order 2-way Butterworth (6dB/oct.), and 1st & 2nd order 3-way crossovers.
- A speaker crossover schematic matching the type you chose will be shown.
- Enter the speaker impedance (Ohms) as needed. This can be whole numbers, fractions, or both. (Ex.: 4 ohms, 3.6 ohms, etc.)
- Enter the crossover frequency desired. For 3-way crossovers, enter the bandpass upper (tweeter/midrange) and lower (midrange/woofer) cutoff frequencies. (*See my notes below regarding 3-way crossovers below.)
The calculator will output capacitor and inductor part values as needed. Parts are labeled to match the the example schematic shown for each type you select.
Reversing out of phase speakers for even-order designs
When building your own speaker crossover and using a 2nd order or other even-order designs, it’s important to remember to reverse one speaker driver to correct the 180 degree out of phase condition.
Crossover capacitors and inductors each add a 90° phase difference, giving even-order (2nd order, 4th order) crossovers a resulting 180° out of phase condition that will affect the sound.
It can result in destructive interference (sound wave cancellation) that occurs in the overlapping range of sound between the two speakers (three speakers in the case of a 3 way system) near the crossover frequency. It will also sound “weird” because the timing of the audio waves you hear conflicts with each other.
Image showing 180 degree out of phase audio waves and the resulting in-phase (0° difference) condition after reversing the speaker.
Fortunately, there’s an easy fix:
- For 2-way crossovers, reverse the tweeter connection polarity.
- For 3-way crossovers, reverse the bandpass speaker (midrange speaker) polarity.
You can do this by reversing the wiring at the speaker terminals in the crossover building stage or reversing the connection polarity label once it’s completed.
This is almost never a problem for ready-made crossovers you buy as this is usually already taken into account when they’re designed.
Why use a Linkwitz-Riley crossover for 2-way crossovers?
Linkwitz-Riley designs are hands-down one of the most commonly used for a number of reasons, one of which is their flat response where the woofer and tweeter crossover points overlap. While it’s true that plenty of other designs exist (Butterworth, Chebychev, Bessel, and others) they do not offer the same frequency response.
They certainly have useful applications but the Linkwitz-Riley (L-R) crossover is generally a great choice for standard speaker systems with a -12dB per octave slope.
The flat magnitude response, low sensitivity to offset, and in-band driver resonances have made the L-R a popular choice among manufacturers.Vance Dickason, The Loudspeaker Design Cookbook (7th ed.)
It’s also not sensitive to speaker driver resonance like some others. If you’re interested in the technical aspects of the different crossover designs available, I’d encourage you to read more.
I highly recommend Vance Dickason’s The Loudspeaker Design Cookbook for more detailed information as it shows examples and covers the topic in good detail. You’ll also learn tons of other speaker design info!
3-way crossover details for the calculator
To get the best results (3-way crossovers are NOT simply an extension of 2-way designs), the calculator uses a 3-way all pass crossover (APC) design with a sufficient frequency range between the high pass frequency and the low pass frequency.
You can also use a general rule based on the ratio of the high pass cutoff (Fh) and low pass cutoff (Fl):
Some great example 3 way frequencies to use are:
- 3kHz/375Hz
- 5kHz/625Hz
- 6kHz/750Hz
Or, simply pick the upper frequency and divide by 8 to get the 2nd. Likewise, you can pick a lower frequency and multiply by 8 to get a good upper frequency.
However, do be aware that 3-way designs have a midrange output with a higher or lower dB level – in this case, the 3-way design provided has a 2.45 dB gain vs the tweeter and woofer. (This is a pretty minor difference however)
Crosspoints closer together than the three-octave ideal will suffer from complicated undesirable interference patterns.Vance Dickason
How precise do crossover capacitor and inductor part values need to be?
I recommend trying to get fairly close to the calculated parts values; exact values are not practical or needed. For example, if the calculator recommends a 10.56mH (milliHenry) inductor, you’d try to get close to 10.5 mH, not 10.56mH. If you found a 10.2mH for example, that would usually be close enough.
Similarly, for the parts themselves, standard tolerance parts are fine for most designs. You don’t need to spend additional money on better tolerance components.
Of course, that doesn’t mean you shouldn’t use better quality or higher performance parts if you’d like – just that for most cases standard (20% – 15% tolerance) is fine.
Typical inductor and capacitor tolerances
The truth is that picking super-precise part values is kind of useless anyway because the components have as much as a 20% tolerance. For example, a 4.7 µF (4.7 microFarad) non-polarized capacitor, 20% tolerance, could have an actual capacitance as low or high as:
- Low end: 3.76 µf
- High end: 5.64 µF
As you can see, trying to pick the perfect parts values doesn’t make sense because they won’t be exactly that value anyway. That’s out of your control. Just try to get it pretty close if possible.
Most inductors are similar as well – especially air core wire wound inductors.
Affordable ways to get better sound performance
Electrolytic capacitors are extremely common in speaker crossovers and filters..but did you know? There’s another little-known way to get better sound and better parts quality without spending a lot: polypropylene, polyester, and film capacitors.
They offer some nice benefits for only a little bit more money:
- Longer life/don’t leak over time like electrolytic capacitors
- Higher voltage handling (great for vacuum tube designs!)
- Better audio performance (better for carrying the audio signal)
- Vertical solder leads may make them easier to use in printed circuit boards or DIY projects
- Some film capacitors are more compact than their counterparts
Film capacitors are generally bipolar (non-polarized) so they’re great for audio designs, but it’s important to always check the specs to be sure.
Also, be sure to verify their voltage rating – you’ll want a rating that’s at least equal to or higher than your amp or stereo’s output voltage generally.
Inductor options
They’re not mandatory, but you can also consider using iron core or metal-core inductors. These types have a more dense magnetic field characteristic, meaning they can be a bit smaller than air core models in some cases.
What voltage audio capacitors do I need?
There’s an easy way to find the voltage you’ll need for audio capacitors in crossovers: you can find the approximate stereo amplifier or radio output voltage if you know the power per channel (RMS or continuous) and speaker Ohms.
Simply use this formula: V = square root(Ohms x Power)
This will give you the approximate voltage at maximum output power. Once you know that, I recommend using capacitors with a voltage rating at least the same if not higher voltage rating.
Otherwise, for standard power levels (not using maximum power out), you can use those up to the next closest value you can find.
Capacitors tend to be rated with standard values such as 16V, 25V, 48V, 50V, and so forth. Using a lower voltage rating part than needed can lead to the capacitor becoming damaged or exploding, leaking electrolyte which can corrode parts and materials.
Off-the-shelf bipolar capacitors sold for audio applications are normally of a sufficient working voltage, but it pays to always check Lower voltage bipolar parts (5V, 16V, etc.) are usually used for low-voltage (line level) electronics.
TIP: adjusting the crossover frequency to match parts on hand
Here’s a helpful tip I’ve picked up after building my own crossovers. If you’ve got parts on hand you’d like to use you might be able to do so by slightly changing the crossover frequency.
For example, let’s say you use the calculator for a 2-way 2nd order design at 3,000Hz, 4Ω:
- C1, C2 = 6.63uF
- L1, L2 = 0.42mH
Let’s also say you have some capacitors on hand that are below 6uF. By changing the crossover frequency slightly you can sometimes make use of parts you already have.
Obviously this won’t always work, and not all speakers are suited for it, but it’s a helpful strategy in some cases. Using a calculator, you can play around with values in seconds and see what works.
Hi Marty. Thanks for the great article. I was reading about Zobel networks and wanted to ask your opinion. I have a 3-way 2nd order crossover based on your calculator and am wondering if I should add a Zobel to the woofer. I’m using the Satori 9.5 8 Ohm woofer that as an Re of 5.8 and a Le of 0.56. Do you think adding a Zobel will improve the crossover?
Hi David. I had a look at the impedance graph for that woofer and it hardly rises at all even up to 1KHz, so I wouldn’t worry about it. The tweeter may be a different story, however, so you could see what it’s specs show.
It may be worth it to add a resonance compensation circuit alongside the woofer, but it’s pretty low (around 20Hz or so) and if you have the means you could set a high pass filter to completely block that since it’s below the human hearing threshold (around 30Hz). Hopefully that helps.
I looked at the impedance graphs for all 3 drivers. They’re all as flat as the woofer, so it doesn’t appear the Zobel is needed. I don’t know why I didn’t look at the before, but pretty obvious once you pointed me in the right direction. With respect to the high pass filter, would that just be added at the start of the woofer circuit with a 30hz cut off? I’ve designed the enclosure to be tuned to 29Hz, so maybe drop that high pass to 28Hz? Thanks again.
Hi David. If you have a high pass function built into your amplifier/receiver, etc., then in that case you could do it in the signal path easily. Some older receivers & etc. have a “rumble” filter for the low frequency noise from turntables which basically does the same thing too.
I definitely wouldn’t try adding a passive high-pass filter for that purpose. You could however put a resonance circuit (series notch filter) in there as they’re pretty easy to make and it’ll flatten it out pretty well. I don’t have Zobel or resonant series notch filter calculators yet unfortunately but hopefully will before too long. There’s several good ones on the web however (I’ve used some in the past).
Hope that helps!
Okay, I’m a bit confused. In you previous response, you said “It may be worth it to add a resonance compensation circuit alongside the woofer, but it’s pretty low (around 20Hz or so) and if you have the means you could set a high pass filter to completely block that since it’s below the human hearing threshold (around 30Hz).” I took this to mean I could add a high pass filter in my woofer section of the crossover. I messed around with high pass filter designs and ruled out using anything with another inductor as the size and cost are just too high.
Since a notch filter adds another inductor, I’m not inclined to go that route, however, I can easily add a Resistor/Capacitor (RC) high pass filter to the woofer section of the crossover. I came up with a 2nd order RC circuit using a 15uF capacitor (Series)/300 Ohm resistor (Parallel) followed by a 1.5uF capacitor (Series)/3000 Ohm resistor (Parallel) located in the woofer circuit prior to the regular capacitor/inductor section. According to the math, this results in a high pass circuit with a cutoff frequency of 29.47 Hz. Doesn’t this accomplish the desired effect of blocking the area below 29Hz where the woofer’s resonance frequency resides?
I made a mistake in the above response, the capacitors in my high pass design are 18uF and 1.8uF, not 15 and 1.5.
Hi David, pardon if anything I mentioned wasn’t clear. Well to be completely honest I don’t think it’s really necessary since there’s virtually no frequency content in music in that low of a range. Therefore I don’t think it’s practical to worry about it unless for some reason you really, really want to.
It sounds like you don’t have any electronic filter options which is unfortunate. The issue I see with what you’d like to try is that while this works with a high impedance input circuit (example: an op-amp filter circuit, with an input impedance on the order of MegOhms) we’re dealing with relatively low impedance in this case. 8Ω is extremely low relative to 300Ω or 3kΩ for example. In the case of using a high pass RC filter with an op-amp for example, the impedance “seen” by the filter circuit/capacitor(s) would be about 300 & 3K Ohms still, but not here.
Generally as a rule of thumb we try to avoid a resonant frequency by at least one octave (if I remember correctly, it’s at least one octave if not more) when establishing a passive filter cutoff frequency which in this case would be about 58Hz.
I believe you should be able to form a bandpass filter configuration for the woofer section of your setup, but again that’d be adding another capacitor/inductor pair which you don’t want to do as you mentioned. That would be about the same effort, if not more, than adding a series notch filter unfortunately.
If you’d like to test your idea you could always try a filter circuit modeling program and go from there.
Thanks again Marty. I’ll probably just leave out the high pass filter then and let the low end do whatever it’s going to do. That will be the easiest and least expensive option and shouldn’t hurt sound quality as the peak resonance is lower than 30hz
Hi,
This a really great article and calculator—very straight forward!
You’ve got the Butterworth covered, but I’m curious about a Bessel arrangement. How would that differ in a 3-way system?
Thanks!
A
Hi Aaron. I’m glad you like the article & calculator as I definitely have worked hard on it. :)
Really good question you have. (Note: when answering here I’ll be referring to only 2nd order crossover designs as 1st or 3rd would be different). So, I think the best way to answer this is to say that using a Butterworth or Bessel design in a 3-way system would mean it’s not an all-pass crossover (APC, more or less flat response output) design and hence would have an increased gain near the crossover points and potentially across the midrange, too.
In the crossover calculator, I use the APC design based on Vance Dickason’s model & recommendation based on having the crossover points far apart enough to provide the best combined response. However, there’s certainly no reason you couldn’t use the others, although there are increased gain versions of the APC shown in the calculator.
If you are working with drivers with a deficiency in part of their frequency response, for example, (as is done sometimes with 2nd order designs too) you could use that to your advantage to help make up the difference.
To be honest the best way to be sure would be to model the crossover behavior in a good program like Xover Pro. Ultimately it comes down to what you’re needing to do but generally you’d have a gain in the midrange with those other types.