Speaker Crossover Calculator + Crossover Building Tips

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.

Note: Javascript must be enabled in your browser to see or use the tool.


speaker crossover calculator section image

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

  1. 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.
  2. Enter the speaker impedance (Ohms) as needed. This can be whole numbers, fractions, or both. (Ex.: 4 ohms, 3.6 ohms, etc.)
  3. 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

diagram of reversing out of phase speaker on speaker crossover

When building a 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 2nd order crossovers a 180° out of phase condition that will affect the sound.

An out of phase condition can result in destructive interference (sound wave cancellation) in the overlapping range of sound between 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.

For example, you can hear the same effect if two speakers are placed near each other with one having its speaker wiring reversed. In that case, you may notice poor bass until one speaker is disconnected due to cancellation.

180 degrees out of phase speaker signal graph

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 second-order L-R crossover is an all-pass configuration which sums to a flat magnitude…

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):

Good 3-way crossover ratio: Fh/Fl = 8 or above.

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)

Generally speaking, the further apart the two crosspoints are, the better the combined response of the drivers will be (three octaves is a good starting point).

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?

examples of speaker crossover capacitor and inductorI 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

examples of film capacitors

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

solid core inductor example

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?

how to calculate audio amplifier output voltage diagram

There’s an easy way to find the voltage rating 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: Volts = square root(Speaker Ohms x Max. Continuous/RMS 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 the next closest value.

NOTE: 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. Still, it pays to 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 use parts you already have.

Example: changing the cutoff frequency to 3,500 would put the capacitor values needed close to 5.7uF. 

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.

About the author

Marty is an experienced electrical, electronics, and embedded firmware design engineer passionate about audio and DIY. He worked professionally as an MECP-certified mobile installer for years before moving into the engineering field. Read more »

Your comments are welcome.
  1. Fantastic guide! I am trying to understand how to calculate the overall impedance of the system. Any clue?

    • Hi Jeroen & thanks for the feedback. Can you specify more about what you’re needing to calculate? (What you’re working with, speaker impedances, etc.)

  2. Marty, Dave here I have worked on my 3 way speaker system and discussed this with you in the past. The current speakers tweeter 8 ohm 1800-22000Hz with 2nd order high pass 2000hz 5 uf capacitor and 2.27mH inductor, the 8 ” midrange 1st order 20 uF polycap with Fs 100Hz ( only info) and the woofer 12 in 8 ohm full range w/o any crossover 50hz-11000hz.
    Any suggestions on placing a second order bandpass to the mid and low pass to woofer 12″ . I guess if I do a 2nd order to the mid I reverse the polarity. The tweeter has a second order now but I have not reversed the polarity on it
    Thanks for the help

    • Hi Dave, yes actually you could use the 2KHz tweeter high-pass cutoff as a starting point for a 3-way design and then get the bandpass/low pass from the calculator.

      The 3-way freq. range examples are for the 3-way speaker set/setup. You pick your frequencies (to the best of your ability, as it’s often a compromise) based on both your goals and what the frequency response is for the speakers. Also, trying to avoid getting to close to resonant frequencies or the lowest stated frequency a speaker can produce.

      We’d try and stay *at least* one octave away from each when that’s possible. For example, having a low-pass frequency of 200Hz or higher for the woofer (due to its resonant freq. of 100Hz) and 3.6KHz for the tweeter. (Where an octave is a halving or doubling of a frequency value).

      For the tweeter, 2KHz is ok if the manufacturer recommends it but otherwise it should probably be higher.

  3. Finally, On you 3 way freq range examples 375hz-3000Khz etc is that each eample for the set of 3 speakers or does each one mean woofer, midrange and ? tweeter. How do you pick which one to use?

  4. Marty, thank you again for all the detailed information. On your diagram of the 2nd order 3-way speaker crossover design the schematics to the midrange is C2 L2 HPF and L3 C3 LPF.
    So what do you think of doing 500Hz 12 db HPF Cap 20 uF in series and inductor 5.1 mH parallel and 4000Hz 12 db LPF cap 2.5 uF parallel and inductor in series .064mH. This info has come from a audio parts company but I already have the polycaps and just need to do the inductors. The strange thing is this is the opposite of your schematics. Which should it be Thanks

    • > So what do you think of doing 500Hz 12 db HPF Cap 20 uF in series and inductor 5.1 mH parallel and 4000Hz 12 db LPF cap 2.5 uF parallel and inductor in series .064mH.

      Well, it’s probably best for you to try simulating it in a crossover design program and see what you get. Otherwise, I recommend just sticking with whatever the calculator provides. The parts placement can be different as long as the crossover is functionally the same electrically.

      If you have more questions it would be better to just contact me directly (see my Contact page).

  5. Can I combine two different crossover types for example, can I calculate for a 1.4khz 4 ohm 2nd order LR crossover, take the low pass and then calculate for 1.6khz 4 ohm 3rd order Butterworth crossover, take the high pass and combine the low pass and high pass from these two designs to make one 2-way crossover?

  6. I have some old custom built 2-way speakers that I managed to blow up one of the crossover caps while having some oscillation problems in my amp. I’m curious why the two sets of tweeter caps were made up of a mylar and a non polarized electrolytic ganged in parallel. One set was a 4.7uf atop a 1uf mylar and the other was a 16uf atop a 1uf mylar. Do you think this was just because a certain value wasn’t available in one cap or was there some reason to run electrolytics with mylars?

    Thanks for your time.

    • Hi Lee. My first thought would be yes, that it’s due to capacitor availablility. Or also it could have been a manufacturing choice based on parts pricing especially in bulk.

      If the mylar ones had some particular performance advantage then using them in parallel with the electrolytic ones *might be* a reason. But I think it’s probably the simplest explanation: parts available or cost etc. at the time it was made.

      Best regards!

  7. Marty,

    I found the reason the cap blew up. Turns out the magnet on the Audax tweeter had shifted and shorted the voice coil. These are small bookshelf speakers and I do not ever remember dropping the speaker. There’s no marks on the enclosure. The glue was completely separated and the voice coil was wedged between the outer plate and the pole piece. And, I’m thinking the oscillations were from the shorted coil.

    I had a replacement cap and tweeter and it’s back working, and it sounds fine. Thanks for the input.


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