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.

Your comments are welcome.
  1. Hi Marty,

    I’ve just installed new tweeters (1 inch) and component mids (5.25 inch) in my Z3 which are all 4 ohm speakers. I bought some JBL crossovers on ebay which I’ve just found out are 3 ohm… is this a major problem?

    The sound isn’t as great as I would have liked, but that maybe due to the limited speaker size, could it be more down to the wrong pairing of crossovers/speakers?



    • Hello Max. By using a different impedance speaker with a crossover designed for another value, the crossover frequency will not be the same. For example, if the original 4Ω crossover had a cutoff at 3.5KHz, using 3Ω speakers would change it to about 4.6KHz. That may or may not be causing part of your issue.

      What you can do is add a 1Ω,10W+ series resistor to each speaker to get 4Ω and see how it sounds then. It may be both the speakers and the crossover.

      (You can also buy a multi-pack of 2Ω power resistors and wire them in parallel to get 1Ω.)

  2. Hi Marty, I have a 2022 Bronco. It has a six speaker set up. I used Polk db402’s to replace the front dash and rear pod speakers. I replaced the 6.5” kick panel speakers with some Rockford fostgate R165x3. All are 4 ohm speakers. The kick panel and dash speakers are factory wired in parallel. They have improved the sound over the factory speakers however, when I installed the kicker key 200.4 amp, I realized the 2ohm load those paralleled speakers were creating was overheating the amp. What would be the best approach to bring that up to a 4ohm load so the amp is happy?

    • Hi there Hugh. That Kicker amp looks like a pretty amazing little unit so it’s a shame it can’t handle a 2Ω load. :(

      There’s not going to be a “perfect” answer in this case, but I can tell you two options you can consider:

      1. Adding a 4Ω power resistor (12.5W or higher) in series with each speaker, or a 2Ω/25W or higher series resistor connected in series to each amp channel and before the parallel speaker connection.

      PROS: 1) Lets you keep your current speakers, 2) easy to do and fairly cheap. CONS: Each speaker will only get 12.5W max. The rest is wasted as heat across the resistors.

      2. Using 2-way component speakers with real 2-way speaker crossovers, installing the tweeters in the dash and woofer/midbass in the kick panels. This does not have to be an expensive set, as some budget or mid-priced sets are really good for $100-$150.

      PROS: 1) Brings highs up better for improved imaging, 2) can sound better, 3) can get full power from the amp, 4) the amp has enough features that would allow you to get the most from it via the DSP/EQ features unlike using 2 sets of full-range speakers.
      CONS: 1) More work to install and tune properly for good sound, 2) additional expense, 3), what to do with your current speakers (?).

      The biggest problem I see is that the amp has only 50W RMS/channel available which isn’t a lot. If you use series resistors, you’ll end up with about the same power available as most head units. If your amp was say 75 to 100W/channel or more, it’d be a different situation.

      If it were me I’d strongly consider using a component set instead with decent quality tweeters (silk or metal dome). So it comes down to your budget and what you’re willing to compromise on too. Hopefully that helps!

  3. Awesome post

    I have 2 way speakers with a 2way crossover. if i want to keep the crossover for the woofer(8ohm) and power the tweeter(8ohm) actively can i just place an 8ohm resister in place of the tweeter on the the crossover?

    • Hi, you could do that but in fact, it shouldn’t be necessary – in 99.9% of crossover designs the tweeter circuit(ry) is separate from the woofer so simply leaving it off should be fine.

      Best regards.

  4. Hey Marty!

    Loving this site! I’m just starting to research building my own crossovers and this information is super helpful.

    I decided that a good first project would be to build a new crossover for an old tower speaker, but I’m already scratching my head…

    The towers are rated at 8 ohms, but the speakers themselves are all different ohm values (tweeter 4, woofer 5, midrange 8). If my amp is set to work with 8 ohm speakers, should I design the new crossover with resisters to match the ohm values of the individual speakers? For example, would I choose a 8 ohm crossover design and use a 4 ohm resister for the tweeter and a 3 ohm resister for the woofer? Thanks in advance for your help!

    • Hi Tony. Yeah if you’re mixing speakers with different impedances there will be some compromises/issues to deal with.

      If the amp is rated for 8Ω minimum, yes you’ll have to make up for it in the case of the 4 ohnms & 5 ohm models with power resistors like you mentioned. Be aware that in the case of the 4Ω speaker, you’ll lose 1/2 the power across the resistor.

      Also, the speakers will develop power & output at different levels since they have different impedances, regardless of the series resistors. But you can definitely make it work if that’s what the goal is (using series resistors and designing the crossover for 8Ω loads). Best regards.

  5. how is the effect when using an electronic rack mounted crossover? seems like I never see them sold as an 8,4, or 16 ohm version.

    • Hi there, that’s because speaker impedance doesn’t matter in that case. Electronic crossovers only work with the low-level audio signal and don’t drive the speakers directly. You’ll need an amplifier for that.

  6. Hey, I’m wondering what the final map impedance will be when you have two 4 ohm speakers ran together on a cross over. Does it still function at the 4 ohm amp load or does the cross over run them in series or parallel to get 2 or 8 ohm?

    • Hi, the amplifier will see the same impedance (total Ohms load) that the crossover sees in most cases. (Occasionally some crossovers use series resistors for the tweeter side output, but that’s less common).

      So it’s important to account for the total speaker impedance 1) to avoid shifting the crossover frequency, affecting the sound, and 2) to avoid causing a problem with too low of an Ohms load at the amplifier side.

      If you wire them in series or parallel, you’ll have a problem from #1 or #2 unless using a crossover that could work with 8Ω speakers for example. To use the same amp or crossovers, you could wire them in parallel and add a 4Ω power resistor in series with each speaker or a 2Ω in series with the parallel speakers.

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