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. Excellent article and very informative! I do have a question though… I have a pair of book shelf speakers that the tweeter circuit in the original crossover went bad on. I want to replace the crossover with one from Parts Express that is rated for 8 ohm drivers. The drivers in my speaker read 6 ohms for the woofer and 8 ohms for the tweeter. Question is, how far up is that going to affect the crossover point of 2.5k? Is there a formula to figure that out?

    • Hi if you know the capacitor value you & speaker impedance you can calculate it yourself on a calculator. For a high-pass 1st order crossover (a single capacitor), you can use:

      Fc = 1/(2*pi*R_speaker*Capacitor_farads)

      For example, if the old 8Ω tweeter used about 8µFarad to get 2.5KHz, for a 6Ω that would be:

      Fc = 1/(2*3.14159*6*0.000 008) = 3.3kHz

      As a helpful rule of thumb, if you halve the speaker impedance, you double the crossover frequency. Inverserly, if you double the speaker impedance, you halve the crossover frequency. So in this case it’s somewhere between (about 33% higher).

      If you like you could add a 2Ω 10W or so resistor in series with the tweeter, after the capacitor, to keep it the same as before and not lose much power across the 6Ω.

      Best regards!

      • Marty,
        Thanks for the equations and help! I do have a few 20w 4 ohm resistors that I could parallel to get 2 ohms. It’s the woofer that is 6 ohms though. The tweeter is already at 8 ohms. Does having one speaker in a 2-way crossover be slightly off impedance pose the same level of frequency change as if both drivers were not correct?

        • Hi CJ. I’m terribly about the oversight with regards to the woofer impedance. I think because it’s so common that I get questions about a different tweeter impedance I messed up reading your comment. Whoops!

          > Does having one speaker in a 2-way crossover be slightly off impedance pose the same level of frequency change as if both drivers were not correct?

          In a 2-way crossover it only affects the crossover frequency for the section that has its speaker impedance changed. However, if you had increased the woofer’s impedance from 8Ω to something else, you could end up with a “gap” in the output as that would make the cutoff lower instead of rise as it does by lowering the Ohms load.

          In this particular case, honestly, if it were me I’d see how it sounds with the 6Ω woofer as they tend to have a natural roll-off so it may not even matter. (By roll-off I mean that it’s common for woofers to naturally lose high frequency output above a certain range in some cases.)

          It may not even be worth adding 2Ω in series anyway, especially if you can’t hear the difference. This isn’t a dramatic change in this case unlike, say for example, change from 8Ω to 4Ω which is doubling the crossover cutoff frequency.

          Personally I would test how it sounds then go from there. Great topic though. Best regards! :)

          • Wow! VERY HELPFUL! So, in my situation (for my own clarification and sanity :) ), I have a crossover rated at 8 ohms at 2.5k and have an 8 ohm tweeter so the tweeter will play 2.5k and up. The woofer being 6 ohms would effectively increase it’s crossover point to (for arguments sake) 3.3k. I’d have an overlap of around 800 hz between the two drivers. I did go a head and wire these up that way and they sounded pretty dang good!

            So glad I found your site! As an old school audio enthusiast (I was MECP Certified in the early 90’s in Philadelphia, had to drive 2 states away to do it LOL) and getting back into the hobby it’s hard to find good sites like yours. Keep it up!

          • Hi CJ. Good to hear it sounded satisfactory for you and interesting to hear that you also were an MECP certified guy too! Thanks for the kind words I’ll keep it up. :) Have a nice week.

  2. hello
    i have a 12.3Ω woofer,8.5Ω mid rang; and 9.5Ω tweeter with a 3 way crossover 2nd order and my crossover model is weah-338.( all the measurement done with a volt-ohm-milliammeter).

    i want to build a 2 channel 3way speakers . my question is what kind of sound in the end i will get?is the so bad or good or i shouldn’t do it ?

    thanks for the useful content
    and sorry for the bad English

    • Hello MJ. Do you know the “rated” (listed on the box or manufacturer label) impedance of those speakers? As those are some very different Ohms measurements you listed.

      To answer your question, you can get good sound from a 3-ways system if it’s done right. However, a good 2-way system can sound excellent as well. If your speakers have mismatched impedances, the problem is they don’t develop the same amount of power so they’ll have different output levels as the volume is increase.

      They can still be used however, if you can live with that issue. You can try out your ideas with my speaker crossover calculator if you like. Best regards!

      • woofer: 12 ohm
        mid rang: 8 ohm
        tweeter: 8 ohm
        stereo i have : 120w max with 8 ohm impedance
        crossover: 2nd order ,3 way, 4-8 ohm and 150w

        Thank you for answer

        • Hi MJ. You’d be much better off replacing the 12Ω woofer with an 8Ω one. Then go from there with the crossover.

          The 12Ω woofer is not compatible with the crossover you have and will leave a “gap” of sound because it will cause the woofer output low-pass crossover frequency to drop. Best regards.

      • I recently bought a 2 way component set of car speakers. What would happen if I did not hook the tweeters up to the crossover only the woofer. I have separate 4 ohm tweeters hooked up parallel to the component crossover and I don’t think u need two seats of tweeters.

        • Hi Aaron. When using only the tweeter or only the woofer portion of a 2-way crossover, it’s fine. The other section simply goes unused – it won’t affect the other.

          Good question! Have a good day.

  3. Hi Marty new to audio, First, how can i know the impedance of an old vintage crossover? suppose it’s 8 ohms. y have a 8 ohms woofer, 5 ohms M and 4 ohms tweeter. can you do the math for me? please. :) and the exactly description i have to tell to get the resistor at the local electronics store? thanks. Max from Argentina.

    And another quick question can I leave the woofer without crossover and add some caps to the M and tweeter ( like sony consumer speaker ) witch caps i have to use?

    • Buenas tardes, Max. Como estas? (Good afternoon Max, how are you?)

      • What type of crossover is it specifically, and what components are in each section? (2-way 1st order, 3-way 2nd order, etc.?) This is very important for me to know in order to help you as much as possible.
      • Do you know the crossover frequency(ies)? What about the parts values such as the capacitance (Usually in microFarads, “µF”, or “mF”) or inductor values in milliHenries (“mH”)?

      Let’s say for example the original used all 8Ω speakers. Changing that to 6, 5, or 4Ω speakers would be a bad idea because it will cause the crossover frequencies to change, affecting the sound you get.

      > “can I leave the woofer without crossover and add some caps to the M and tweeter ( like sony consumer speaker ) witch caps i have to use?

      I’m not sure what you mean specifically here. If you want a 3-way system, at the minimum, you’ll need an inductor for the woofer, a capacitor + inductor for the midrange, and a capacitor for the tweeter. See here: https://soundcertified.com/speaker-crossover-calculator/#SPEAKER_CROSSOVER_CALCULATOR

      If you have specific questions or details to share then maybe I can help but it’s extremely difficult without specifics. See the top menu > Contact for how to reach me. Saludos/best regards. :)

  4. Hi there I successfully hooked up 4 six inch klipsh mids in series parallel and I have really nice sound but I would like to hook a bass blocker to just one to get a little more tweeter out, with that said will it affect the rest of them or just the one it’s hooked up to? Since all of them are connected! I hope I am clear enough?

    • Hello there. If you have the speakers connected in parallel, connecting a crossover to one won’t affect the others. Each speaker will have a full-range signal of its own from the amp so it’s not an issue.

      • Hello, I have 2.5 ohm woofers and 4 ohm tweeters according to my multimeter. I want to connect them to a 4 ohm two-band filter. The signal source will be an original bmw e46 receiver. Will an additional resistor be needed or should I try without one. I add that all the listed elements are of high class – Bose woofers, tweeters from Logic 7 and Helix crossovers.

        • Hi, when you measured the woofer DC resistance, that’s not the same as the actual impedance rating. The woofers are most likely 4Ω as the DC resistance alone is typically somewhere around ~60% of the impedance.

          You shouldn’t need to add any resistance added for normal use with a 2-way 4Ω compatible crossover. If you wanted to be particuarly precise, you can do so, but you’d need to measured the impedance graph yourself over the 20-20KHz range using a test device.

          The woofer’s impedance will be closer to 4Ω with a musical signal applied, so I wouldn’t worry much about it in this case. Best regards!

  5. I seen this thread hoping to find an answer to my dilema. I have yet to find a similar scenario in forums and was hoping someone here can help me. So I have a dual voice coil 4 ohm speaker configured in series for 8 ohm then I have two 4 ohm speakers wired in series to also make an 8 ohm series. then I have both sets of 8 ohm series setups connected in parallel to create a 4 ohm channel with three speakers in a parallel series. the dual voice coil speaker is a subwoofer I have a crossover rated to the wattage of such said speaker. the impedance of the crossover is four ohms and it cuts all frequencies out higher than 120hz at 4 ohm. if I hook this crossover to this subwoofer dual voice coil speaker will it perceive the 8 ohms of the speaker as it is wired in its own series series and cut the frequency at 60hz or will it perceive the 4 ohms of the entire circuit of speakers and cut the frequency at 120hz? I would love to know. either might be a favorable effect but I would really like to know. Thank you

    • Hi, it depends on how you connect it. If you only connect it to the 8Ω series wired DVC subwoofer, will have a cutoff of 60Hz. If you wire *all* speakers (a 4Ω load total) to it, it can work at 120Hz.

      Best regards.

  6. Sorry but I no understand why is use speaker with other impedance change the crosower frequency. If the formula is F=1/[2*3.14*√(L*C)] -there is no R. I use bad formula?

    • Hello, Lex. For a high-pass crossover (using a capacitor in series) the formula is: F = 1/(2*3.14*R*C). Therefore, changing R (the speaker impedance) will affect the frequency.

      Best regards!

      • F = 1/(2*3.14*R*C) is for first order high-pass crossover (only a capacitor)? -If I good understand. My formula is for second order no? Or even there(second order) is speaker resistance change the frequency? Or only the shape of the amplitude? Thank you fo answer..

        • > My formula is for second order no? No, as the formula you wrote in your original comment was for an LC resonant circuit, which is something very different. Hence why it was missing the “R” variable. You cannot have a crossover formula without a resistance/impedance.

          The formulas depend on what type of 2nd order crossover you’d like to use. For example, Butterworth, Linkwitz-Riley (very common), etc. The L and C values are in separate equations.

          For example, Linkwitz-Riley 2-way:
          • C1 = .0796/(R_tweeter*f) L1 =.3183*R_tweeter/f
          • C2 = .0796/(R_woofer*f) L2 = .3183*R_woofer/f

          > Or even there(second order) is speaker resistance change the frequency? Or only the shape of the amplitude? For any 1st, 2nd, 3rd, etc. crossover, changing the speaker Ohms load will affect the crossover frequency.

          Best regards.

          • “For example, Linkwitz-Riley 2-way:
            • C1 = .0796/(R_tweeter*f) L1 =.3183*R_tweeter/f
            • C2 = .0796/(R_woofer*f) L2 = .3183*R_woofer/f”
            Right that what I no understand..
            If in the formula for capacitor is the resistance divisor and for the induction he are multiplicating -than the final frequency is not stay the same? (1×1 is same like 0.5×2..)
            One example(Linkwitz-Riley 2-way):
            1000Hz 4Ohm -C=19.9uF and L=1.27mH
            1000Hz 8Ohm -C=9.95uF and L=2.55mH
            When I count the frequency from values od capacitor and inductor F=1/[2*3.14*√(L*C)] then:
            For 4Ohm: F=1/[2*3.14*√(0.000019F*0.00127H)]=1027Hz
            For 8Ohm: F=1/[2*3.14*√(0.00000995F*0.00255H)]=1007Hz
            The different is made only by rounding the values.

          • > If in the formula for capacitor is the resistance divisor and for the induction he are multiplicating -than the final frequency is not stay the same? (1×1 is same like 0.5×2..)

            Hi, maybe there’s a misunderstanding? I don’t think changing the L & C values was in your original question. 1st order, 2nd order, etc… crossovers use additional crossover stages. Therefore each is still affected by the Ohms load that is connected assuming the L or C values are fixed values and do not change.

            This is because of the affect of the rate of current flow over time in inductor-resistor (LR) and capacitor-resistor (CR) circuits being limited by the resistance/impedance value.

            To clarify:

            • If you DO NOT change the L or C values, changing R does affect the crossover frequency.
            • If you change the R value(s), you must change L & C values to correct for that in order to keep the same crossover frequency as before.

            F=1/[2*3.14*√(L*C)]” <- But again, this formula doesn’t apply to crossovers. It’s for LC resonant circuits. This applies to resonant impedance compensation (notch filters) but not a crossover.

            If you have additional questions, I can help you better by email (see my Contact page in the menu). Best regards.

          • Thank you one more time. So it is really important to use the measured impedance at cut-off frequency to calculate the parts for crossower.

          • Well, in practical terms you just need the average (nominal) or typical impedance as that’s usually close enough.

            The impedance will never be a perfect value, but yes if you want to be more precise you can use a test device to get the impedance graph or manually measure it using a multimeter & test setup over a range of frequency points. Best regards!

          • Hi, the correct way to match a tweeter to a woofer is 1) use the same impedance tweeter as the woofer, and 2) use a resistor network/L-pad to decrease the tweeter’s volume. I have this covered here already: https://soundcertified.com/how-to-reduce-tweeter-volume/

            If you use a 16Ω tweeter with a 4Ω woofer, when you increase the power/volume they will be mismatched because they will not develop the same power from the amplifier. Best regards.

          • Thank for fast answer! It is increase the mismatch? Yes, I know it is normaly matched by resistors… Only I want to know, if teoreticaly the tweeter resistance is 4 time bigger, than at same voltage(conected paralel with woofer) the current throught tweeter is four time smaller -so at same voltage it is mean four time smaller watage(-6dB).

          • Hi, well anytime they are not the same there will be a mismatch in output volume, but yes it will be even higher witih a 16Ω tweeter. Yes, if the impedance is x4 higher the current is 1/4th of a 4Ω speaker.

            However, because power is a product of the square of voltage (or current) as the amplifier’s output increases, the difference in their output will not have the same “curve” if you were to graph it. In other words, the difference between their dB outputs would not be proportional as power is increased.

  7. I have two 8 ohms speakers ( w&t). The woofer goes from 29-3,000 and the tweeter goes from 1,300-20,000. Should the crossover be in parallel or series. Thanks.

    • Hi, what type of crossover? A 2-way crossover will already be designed to connect the tweeter & woofer in parallel.

      If you’re adding your own, you can wire a capacitor in series with the tweeter and inductor in series with the woofer. These would then be connected in parallel at the speaker input terminals. Best regards!

  8. how do you allocate the wattage to each driver……….. example 70% woofer 30 % tweeter? Thank you excellent work on the site.

    • Hello Bruce. Yes you can reduce the power to a speaker via an L-pad/resistor network. This is what we do to reduce tweeter volume – it’s the same principle.

      To make it simple you can use my calculator here to play around with the values until the power reduction is what you like: https://soundcertified.com/l-pad-calculator/#L-PAD_CALCULATOR

      If you enter the total max. power, my calculator can show you how much power the speaker will receiver based on the attenuation network.

      Hopefully that is clear. Glad you like my site also. :)

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