How to install a crossover

Running tweeters, speakers, and subs in an active system


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Passive Crossovers

Passive crossovers for component speaker systems are very simple to install. They each go between your amplifier and a speaker and do not require a power connection, a turn-on lead, or grounding. You connect the speaker wire coming from your amp to the crossover's input. Then the tweeter gets wired to the tweeter output, and the woofer to the woofer output. That's it. The most challenging part of installing a passive crossover may be where to mount it, but most component crossovers are small enough to fit inside your car door near the woofer's location.

Examples of in-line crossovers

Examples of in-line crossovers

There's another kind of passive crossover, called in-line crossovers, which go between your receiver and amp. They look like little cylinders with RCA connectors on each end and simply plug into your amplifier’s inputs. In-line crossovers each come set to a specific crossover frequency and can’t be adjusted. Another disadvantage of using them is that they react differently to different amplifiers, possibly changing their crossover points unpredictably.

Active Crossovers

Installing an active crossover requires a bit more work. You'll mount your crossover securely, preferably near the amplifiers; give it power, remote turn-on, and ground wiring, like the amps have; and get signal from the receiver and send it to the amps. Once you've done the work, however, you'll gain new control over your music, being able to tune your sound system so that all of the speakers can give you their best performance.

Finding the right spot

You'll want to put your crossover in a location that won't take up too much space in your vehicle, but is accessible enough for you to be able to make adjustments. Usually, you'll just make the initial adjustments to fine-tune the sound and then leave it. But sometimes, you may get into the mood to just tweak your system or give it a different sound for the day. You need to securely mount your crossover so it won't become a flying liability in the event of an auto accident.

Audio Control DQXS and  a Boston GT-50

Audio Control DQXS 4-way crossover with 6-channel EQ (left) getting mounted next to a Boston GT-50 5-channel amp

Do not bolt your crossover directly to metal — that's inviting noise problems, like ground loops which hum or buzz. You could use rubber grommets around the mounting screws to isolate the case. Or you could mount the crossover on a wooden board and attach that to the car body. Some people even mount their crossover and amps on the same board, for convenience. A crossover can actually go anywhere between the receiver and the amp, but most people mount theirs near their amp, making it easier for connections and for future system expansion.

Wiring for power

You'll need to provide 12-volt power from your car battery to operate the crossover just as you would to power your amp. The power and ground wiring for your crossover do not have to be the heavy-gauge stuff that you use for your amp — typically wire as thin as 18-gauge wire will be fine. A distribution block is a good way to get power for your crossover via the same main power cable as the amp uses. You'll also need a solid, noise-free grounding point — it's best to ground your crossover at the same place as your amp. Make sure the grounds get attached tightly to the metal chassis of your vehicle, with all the dirt and paint removed where contact is made.

As for the turn-on lead, you can usually tie it into the turn-on lead for your amps. However, a receiver's turn-on circuit has a limited capacity and could fail if there're three or more devices to be turned on. If that's the case, you'll need a relay, that'll get triggered by the turn-on circuit but get its 12-volt power from another source, like the fuse box. If you bought your crossover from Crutchfield and need help with such a relay network, you can call our tech support department for free advice (please have your invoice handy).

Signal wiring

You get the input for your crossover via RCA patch cables from your receiver. If your receiver doesn't have RCA outputs, you can use a crossover that accepts speaker-level signals for inputs. Or, you can get a line output converter to step the speaker-level signal down to preamp level. Lastly, you run more patch cables from the crossover outputs to the amplifier inputs — highs to the tweeter amp, mids to the woofer amp, and bass to the subwoofer amp, for example

Make sure the patch cords supplying the musical signal to the crossover and amplifier are kept well away from potential sources of noise, such as the amp's power and ground cables, the vehicle's brake light wires, or rear window defroster wires.

Kicker KX3 3-way crossover

Kicker KX3 3-way crossover

Crossover points

Crossover points are the frequency settings of a crossover that represent the points in each output band where the signal is attenuated, turned down, by one-half — a 3 dB drop in power. The intention is, that at each crossover frequency, two adjacent drivers (tweeters, speakers, or subs) are playing the note at one-half power — so the result is full power at each crossover point.

The crossover points you choose ultimately depend on the frequency response of each component driver in your speaker system. Check out the frequency response specifications of each of your drivers and use those frequencies as preliminary crossover points. If you can't find any such specifications, start with 100 Hz as the crossover point between your subwoofer and mid-bass drivers, and 2,000 Hz for the midrange-to-tweeter transition point.

Adjusting frequencies

Unlike the following tune-up tips that take into consideration your music's tone and volume along its entire spectrum, you adjust crossover frequencies to eliminate the distortions a driver will put out when it tries to reproduce notes it can't play well, at the extremes of its frequency response. So, for instance, if you hear your mid-bass/midrange driver distorting on low notes, you adjust its crossover point higher, so it won't even try to play those notes. The same goes for the midrange/tweeter crossover point — you move the crossover point to eliminate distortion — higher to clean up the tweeter's sound, lower for midrange clarity.

Kicker Front Row signal processor

Kicker Front Row signal processor

Now you get to tune your system

The first objective, in setting up a crossover, is to end up with each band of frequencies — for the tweeters, midrange speakers, and subwoofer, for example — playing at the same volume. Next, you apply the EQ curves and other tone adjustments you like in your music. Then, you do it all again, re-setting the crossover to compensate for the equalization adjustments. Some people even tweak the EQ again after that, and on and on, until it sounds perfect to them.

You start off by playing familiar music with all the tone and EQ controls off or set flat and the amp gains down low. All crossovers are different, but you can use the following as a general guide for setting a 3-way crossover:

  1. Find the top level at which your receiver plays your music cleanly. Turn up the volume until music distorts, then turn it back a little.
  2. Set the input sensitivity of the crossover, if it has it. Crossovers with this feature will also have clip indicator lights that help you set this control.
  3. Set the level for each output so they play evenly.
  4.  Set the gain for each pair of amplifier channels. Turn it up until the music distorts, then turn it back a little.
  5. Re-set the crossover output levels to balance the highs, mids, and lows playing from each component. Try to make the system's total response flat— high notes, mid notes, and low notes all playing at the same volume.
  6. Re-set the amp gains, to compensate for any crossover output adjustments.
  7. Re-set crossover output levels again.
  8. Apply EQ or tone adjustments at the receiver. Adjust every available control and /or boost to allow your music to sound its best. Turn on the bass boost, if you use one.
  9. Because you've added equalization, you'll have to slightly re-set the crossover and amp gains again. Find the top level at which your receiver plays music cleanly. Turn up the volume until the music distorts, then turn it back a little.
  10. Re-set the input sensitivity of the crossover, if it has it.
  11. Adjust the level for each crossover output to blend them together smoothly.
  12.  Set the gain for each pair of amplifier channels. Turn it up until the music distorts, then turn it back a little.
  13. Re-set the crossover output levels to balance the highs, mids, and lows playing from each component. This time, your goal is to make it sound great, not flat.
  14. Adjust the amp gains, to compensate for any crossover output adjustments.
  15. Adjust crossover output levels again, if necessary.
  16. Adjust the tone at your receiver again, to allow your music to sound its best, and enjoy.

Audio Control 2XS 2-way crossover

Audio Control 2XS 2-way crossover

  • Rolando Delos Santos from Philippines

    Posted on 4/25/2015 11:46:00 AM

    what might happen if iwill directly attach speakers to amplifier without using crossover?

  • Buck Pomerantz from Crutchfield

    Posted on 4/27/2015 9:50:23 AM

    Rolando, A full-range speaker should play fine without a crossover. A crossover filter could be applied to clean up the sound - remove high notes from a subwoofer or low notes from a small speaker that can't handle bass - but it isn't absolutely necessary. For a tweeter, however, it is absolutely necessary to employ a high-pass crossover filter, or else low notes will tear the tweeter apart.

  • Jake Peterson from Los Angeles, California

    Posted on 5/9/2015 2:45:27 PM

    Hello Crutchfield, I have a pair of Kenwood Excelon component speakers for the front of my car. They have an in-line crossover. The sound is fine but I feel as though the 18 watts that are coming from my heading are not enough. So my dad gave me a pair of his Boston crossovers (like the ones pictured at the top just made by Boston). My question to you is, can I replace my inline crossovers with the other ones, and then amplify them later?

  • Buck Pomerantz from Crutchfield

    Posted on 5/11/2015 10:08:17 AM

    Jake, The crossovers that came with your Kenwood components were designed to work with those specific tweeters and woofers to create a balanced and smooth sound. The Boston crossovers were designed for a different set of drivers. You'll get no benefit from changing crossovers, and it might even damage your tweeters or woofers. When you do add an amplifier you should continue using the Kenwood components' in-line crossovers. Later, if you want a more advanced, but not necessarily louder system, you could "go active" and lose the in-line crossovers, and run each tweeter and woofer with its own amplifier channel crossed-over, filtered appropriately for each driver.

  • Walker from Kelowna

    Posted on 9/29/2015 5:10:03 PM

    Hey Buck, I've read online that it's better to install crossovers as close to the speakers as possible and I was wondering if this is true, and why? The thing is I am looking at putting in HSK165XL speakers in my 01 Jetta TDI but the passive crossovers turned out to be huge. The crossovers alone are around 6" x 4" so my doors may not fit them with alterations. I was hoping you could help me on this one. Would simply having the crossovers in the trunk next to the amp work? Thanks so much for your time and efforts. TL:DR Is it better to install crossovers closer to speakers? What are the pros/cons?

  • Buck Pomerantz from Crutchfield

    Posted on 9/30/2015 11:19:46 AM

    Walker, There are no factors that I know of that would dictate where a crossover should go between amp and speakers. Maybe some folks don't want to have to run two sets of speaker wires per side in their installs. Go ahead and mount your crossovers in a convenient location.

  • Wayne arringron from Chantilly

    Posted on 10/20/2015 6:50:24 PM

    Is there a good/bad distance to mount a passive crossover? I don't want to really mess with the wiring in my vehicles doors but want to add component speakers. I wanted to put the crossover in the trunk and run the wires for the tweeter and midrange separately from the front to the back.

  • Buck Pomerantz from Crutchfield

    Posted on 10/21/2015 2:46:41 PM

    Wayne, Because the inputs and outputs of passive crossovers are amplified, speaker-level signals not prone to interference, it really doesn't matter where you mount them. Go ahead and mount yours in your trunk.

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