What Happens If I Use A Different Impedance Speaker On A Crossover? Can I?

Have you ever wondered what really happens if you use a different impedance speaker with a speaker crossover? It’s a great question!

As it turns out, the speaker impedance (Ohms) does make a difference in how a speaker crossover works and affects the sound. I’ll explain it all in detail in a way that anyone can understand.

What is a speaker crossover? What does a crossover do?

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 often called “passive” crossovers because they pass signals without need a power supply unlike electronic (“active”) crossovers. 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.

They’re different from electronic crossovers in that instead of being connected to the signal path (RCA cables, for example) speaker crossovers are connected to the output of amps or stereos. The speakers are then connected to the crossover’s speaker connections.

diagram showing how a 2-way speaker crossover works

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. Speaker crossovers work to separate the sound sent to certain speakers for improved sound, lower distortion, and to control over how speakers are used. For example, they block bass that tweeters can’t produce and highs that a woofer can’t produce well.

Inductors and capacitors have some really interesting (and really useful!) properties when an electrical audio signal flows through them:

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

When a capacitor or inductor has a signal applied to it past a certain frequency range called the crossover frequency, corner frequency, or cutoff frequency, the amount of signal it allows to pass is lowered, making it act like a filter.

This means the speaker will receive less and less of the speaker signal that we want to block, reducing the volume output for that unwanted range of sound. It’s important to understand that the frequency at which this happens depends on the speaker impedance (Ohms load) connected.

Speaker crossover orders (slopes) and designs

Image of a tweeter used with inline bass blocker capacitor speaker crossover example diagramWhen used in series with a tweeter, a crossover filters out damaging and distorting bass that it can’t handle. When used alone, a single capacitor is a 1st order (single-stage) crossover with a slope of -6dB per octave – the most basic level.

Crossovers come in different designs for different types of audio tailoring & performance levels, but they all work in the same basic way. They’re designed with “orders”, or stages, which when added make their filtering even better at blocking unwanted sounds from reaching speakers.

Crossover slope diagram and examples illustrated

For example, here’s a list of common order crossovers you’ll often see:

  • 1st order: Not very steep -16dB/octave), consists of a single capacitor or inductor in series with the speaker.
  • 2nd order: Better -12dB/octave filtering, using TWO components for each speaker.
  • 3rd order: Even better, with -18dB/octave filtering, using THREE components for each speaker.

Crossover filters are always multiples of 6 decibels (dB) because of how the components work. A “steeper” (higher) crossover order just means it’s more effective at blocking the range of sound frequencies we don’t want to reach the speaker.

What is speaker impedance? How does speaker impedance work?

What is speaker impedance diagram

Speaker impedance is the total amount of resistance a speaker has due to both the resistance of its wire coil and the inductance of the wire coil loop. Impedance is rated in units of resistance called Ohms.

Just like you can’t have a short circuit across a battery, an amp or stereo needs some amount of speaker load impedance to limit how much electrical current the radio or amp tries to supply.

Unlike a straight wire that goes from one point to another when you hook up power, the voice coil’s wire winding forms a loop that has an electrical property called inductance. Inductance is a bit different from resistance as it changes as the frequency changes. It’s called inductive reactance.

For nearly all speakers, this means that the real impedance (the total resistance) actually changes somewhat as the music plays.

When we refer to the impedance of speakers, most of the time we’re referring to the category (general Ohms range) of the speaker used to match home or car stereo amplifiers.

Resistance measurements, in units of Ohms, are sometimes shown by using the Greek symbol Omega: “Ω”

How does speaker impedance work?

how does speaker impedance work diagram

When a musical signal (made up of alternating current) drives a speaker it creates magnetic fields as electrical current flows through the tightly wound wire voice coil. What’s interesting is that a coil of wire develops magnetic fields around it that resist the flow of current when this happens.

That’s where the frequency-dependent part of a speaker’s impedance comes from.

(This also happens with other electrical devices too, like motors, engine spark plug coils, and more. They also deal with electrical resistance as alternating current (AC) is applied.)

What happens if I use a different impedance speaker on a crossover?

Crossover shift due to speaker impedance change explained diagram

Diagram showing what happens when you change the speaker Ohm load connected to a crossover: crossover shift occurs. This means because it was designed for a different speaker impedance, the frequency at which it works changes.

Crossover shift when using different impedance speakers

As I mentioned earlier, speaker crossovers are based on parts (capacitors and inductors) that work as filters according to the speaker load they’re connected to. Because of this, when you change the speaker impedance you change the crossover frequency and the sound.

You may notice several problems after doing this:

  • A “harsh” sound from woofers or midrange speakers. Tweeters may sound distorted and begin to “break up” at a lower volume than they used to.
  • A “thin”, weak quality to the music.
  • Gaps in the sound ranges you should be hearing.

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!

What happens to a crossover when I half the speaker impedance?

When you change the speaker impedance connected to a speaker crossover it can significantly shift the crossover’s cutoff frequency. As a general rule:

  • Halving the speaker impedance (ex.: 8ohms to 4 ohms) doubles the crossover frequency (Ex.: 3.5kHz goes to 7kHz)
  • Doubling the speaker impedance (ex: 8 ohms to 16 ohms) halves the crossover frequency (Ex. 3.5kHz goes to 1.75kHz)

We don’t want that because it allows the speakers to be sent a sound range they’re not suited for and sounds bad. In the case of tweeters, bass & midrange are bad because they can’t produce it properly. In fact, after a certain power level tweeters can be damaged when driven hard by bass frequencies.

Similarly, many woofers can’t produce high frequency sounds well and can sound terrible.

Normally, if you change the speaker Ohms load you’ll have to replace the speaker crossover as well to match the Ohms load.

However, there is a workaround that offers some hope…

How can I use speakers with a different impedance? Is it possible?

How to use a different speaker impedance with crossover diagram

The great news is that it is possible to use a different speaker impedance with a speaker crossover it’s not designed for! There are some compromises you’ll have to make, though.

How to match a different speaker impedance to a crossover

This is actually pretty simple! To match a speaker impedance to a crossover:

  1. Case #1: a speaker that has a lower impedance: You can add a resistor in series with the speaker to bring the total Ohms load up to what the crossover needs. You’ll need a resistor with enough power handling (called a “power” resistor) to avoid it overheating (see below).
  2. Case #2: a speaker that has a higher impedance: You can add a resistor in parallel with the speaker to bring the total Ohms load down to what the crossover needs. 


  • You can use an 8 ohm speaker with a 4 ohm crossover by connecting an 8 ohm resistor in parallel with it. The end result is 8 Ohms/2 = 4 ohms the crossover will see.
  • You can use a 4 ohm speaker with an 8 ohm crossover by connecting it in series with a 4 ohm resistor. The end result will be 8 ohms total seen by the crossover.

What is a power resistor?

Audio power resistor examples

Examples of power resistors commonly used with speakers. Unlike the tiny resistors used in electronics, these can handle much more power and won’t burn up due to heat. They’re available from electronics suppliers including speaker component retailers.

A power resistor is just a larger-size resistor that can handle a lot more power & heat than the small ones commonly used on electronic boards. They’re actually fairly inexpensive, too ($5 or so for 2 to 4 in a pack) and are commonly used for custom speaker projects.

For speaker systems, I recommend using one with a power rating of 25 watts or more to be sure. For car stereos, you can often get away with around 10W to 15W, however.

The drawbacks of using resistors to match a crossover

Like I said earlier, it’s not without a compromise. You’ll have to live with a few things depending on which case you’re dealing with:

  • Adding a resistor in series with a speaker will drop the maximum power & volume available to it. In the case of a 4 ohm speaker and a 4 ohm resistor, this means you’ll lose 3 dB of volume (a tiny amount) but the power will always be 1/2 of what it used to be.
  • Adding a resistor in parallel with a speaker means the power will be split between the two. In the case of an 8 ohm resistor parallel with an 8 ohm speaker, a each side will receive 1/2 of the power formerly sent to one speaker. (Ex.: a 50W amp would now deliver 25W max to the speaker)

Ordinarily, I’d recommend using the correct crossover but if you’re “in a pinch” this solution is a great way to get your speakers going and still sounding good.

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. Hi and greetings from Vancouver BC; I’m a 74 yr old hi fi enthusiast as well as a musician.
    I enjoyed reading a lot of your material just this evening and would like to complement on you straight forward explanations.
    I’ve been trying to make up a speaker cabinet with two 15 ” power speakers but of the all range type. I don’t know the specs so having an awful time. It’s to be used with a software pipe organ program and hardware console with very many frequencies but a generous bass as well !! . Trying to spread out the various ranks ….. :0)
    Anyway thanks for your efforts and information.

  2. Hi, and greetings from Cali, Colombia.
    I am a 47 yo Musician, and have been messing arround with electronics with almost no knowledge, but still trying to understand. and enrich concepts and knowledge with yours. thanx 4 that.
    Mi cuestion is how so i kno (or mesure) the max power and the impedance alowwed by a crossover?
    I got this “Logic soundlab 2 way crossover” from flea market, it has 6 screw terminales labeled: AMP, MidWoofer, & tweeter. it also has a switch with 3 positions: -3dB, 0dB & +3dB. but I totally ignore the max values I can connect to the AMP terminal which I guess should come from the amp (Zansui PA-450C PA amplifier) which has a single two pin (mono) output. and this type of amp usually come with a range of impedance like “4 – 16ohm max.” And usually 40 or 50 watts RMS out-pow. So I was wondering if I can follow the rule of (divide multiply, serial – parallel) to match the output, out of the crossover and I wonderif this crossover has a max or correct output power/impedance, since it seems to be for cars I guess it must come for 4 ohm. Of cousrse I googled the picture and googled “Logic soundlab 2 way crossover” but I could find the model I own which is silver (mirror) finish.
    SO if anyone knows the exact model or specs I’ll appreciate to have light.

    • Hola Paul, como estas? Tengo experiencia/amigos en Medellin. :) (Hello Paul, how are you? I have experience/friends in Medellin.)

      It’s difficult to know the power rating if it’s not specified because it depends on the ratings of both the inductors & the capacitors. However, here are some clues to help:

      If the capacitor(s) have a voltage rating on it/them, you can use that to find the power limit. For example, if a capacitor lists a rating of “24V max”, we can determine the max rating using the speaker impedance:

      P = V^2 / Ohms = (VxV)/Ω. For example, (24)^2/4Ω = 144 W. Of course, the inductors have a current limit as well, but it’s usually not listed on it. More than likely however the crossover can handle 100W or even more without a problem.

  3. Hi Marty- I appreciate your effort with this page. I imagine this is covered somewhere above, but I’ll ask anyway. I have an amplifier that produces 50 watts @ 4 ohms (per channel) and 30 watts @ 8 ohms. Given this, I want to use two 8 ohm speakers (full-range and tweeter) in parallel so that the amp sees a 4-ohm load. However, my crossover is 8 ohms – a Dayton Audio 2khz high-pass.

    Should I get a 4 ohm version if I want to run the speakers in parallel? I imagine this is may be a dumb question – but I am confusing myself! Thanks.

    • Hi Tim & thanks for dropping by. You could do this in two ways:

      1. Add a second 8Ω crossover to the 2nd speaker then wire all of those in parallel for 4Ω total.
      2. Use a 4Ω crossover then wire the speakers in parallel to its output.

      Best regards!

  4. Hi Marty, your tutorials on Crossovers are excellent, thank you so much for writing them!

    I have an odd question that I can’t find any answer to, but you will probably know.

    If I use a 3-way passive speaker-level crossover, but I don’t hook up all three speakers, I only hook up the tweeter and mid, will it still work for the tweeter and mid??? Or would that burn out the crossover? Or damage the Speakers? Or damage the amp?

    I don’t want to just try it and see what happens. All speakers, amp and crossovers are 4-ohm rated.

    I’m not sure if there is some “It depends…” here, but if you need more info on what I am building, let me know and I’ll add to the comments.

    • Hi Alan. I’m glad you like my articles and thank you for your kind words. :)

      If you don’t use a given speaker section of a crossover it’s fine. The crossover sections are normally independent of each other even though they’re related by the crossover point/frequency. The crossover will still allow the stereo or amp, etc. to “see” the correct Ohms load for the speakers that are in use.

      The missing speaker(s) simply wouldn’t have audio frequencies in its range sent to anything. If you would feel better, you could always replace the speaker in question with a power resistor. You’d get the same result as a speaker being used but no audio produced.

      Sure, if you’d like to share what you’re building I’m curious to know. Best regards!

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