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Five things to consider when setting up a subwoofer in your car

Understanding how to get the bass you want

Heads up!

Welcome to this article from the Crutchfield archives. Have fun reading it, but be aware that the information may be outdated and links may be broken.
JL Audio subs

JL Audio's 10" (left) and 12" (right) W0v3 subwoofers. The size and number of subs you choose will largely depend on the amount of room you have available.

When it comes to picking the right sub for your system and setting it up to deliver exactly the kind of bass reproduction you want, we recommend that you consider five elements:

  1. Subwoofer size
  2. Enclosure type
  3. Power
  4. Impedance
  5. Low-pass filters

Here’s a quick look at how all of these elements work together.

Subwoofer size: how big should it be?

Really, the size of sub you choose is mostly a pragmatic matter — it depends primarily on the amount of space available in your vehicle. If you’re looking for maximum slam, consider the largest sub that your space allows. But if your space is limited, or you want to maximize your remaining cargo space, even adding a small sub, such as an 8" model, can deliver forceful, deep, and satisfying results.

In terms of performance, generally speaking, a subwoofer with a larger cone is capable of playing deeper bass than one with a smaller cone, simply by virtue of being able to move more air. How noticeable that difference is, however, is a matter of debate, and really depends on the other four factors we’ll talk about next. That’s why you should feel comfortable letting your available space dictate your sub size.

[Shop for component subwoofers]

Enclosure type: which should you choose?

Every sub needs an enclosure in order to perform, and the type of enclosure (also simply called a box) you choose for yours will have the biggest impact on the kind of bass reproduction you get. The two most common types of enclosure are sealed and ported. Sealed enclosures are airtight, while ported enclosures feature a vent or a tube that allows air to pass in and out of the box.

When trying to describe the difference between the sounds of sealed and ported boxes, you’ll often hear that sealed boxes are for "tight and accurate" bass, while ported enclosures are "loud and boomy." While this is useful as a shorthand explanation, it doesn’t quite fully capture what each box does and how it does it.

Sealed sub enclosure

Sealed enclosures

A sealed enclosure will provide an airtight home for your subwoofer, for tight, natural-sounding bass. With sealed boxes, what is often referred to as "tight" bass is the result of what’s called linear, or flat, bass response. This means that across the bass spectrum, the output of a sub in a sealed box will gradually and evenly decline as the bass notes get lower, without any excessive spikes or dips. Fans of music such as classical or jazz will get a lot out of a sub in a sealed enclosure, as the linear response ensures that instruments like the cello or the low keys of the piano will sound clean and natural.

A ported sub enclosure

Ported enclosures

A ported enclosure features vents (at the bottom of the box shown) that let air move in and out of the box to reinforce the sub's output for forceful, resonant bass. Ported boxes are great for people who want to get lots of low-frequency output. With a ported box, when the sub moves forward it creates a bass note. Then, when it moves backwards, it forces air out of the box’s port, which reinforces the bass output and reduces air pressure inside the box itself, allowing the cone to move more freely. This means you’ll get more output from a ported box than you will from a sealed box receiving the same amount of power — that's why ported subs are often described as "louder."

The "boomy" aspect of a ported box is a little trickier to understand. The port of a given box will have a specific "tuning frequency" (you can find this in the "Details" tab of a given box's web page when you’re shopping with us), which describes the frequency at which air naturally resonates through the port.

Air coming out of the port will reinforce the bass that the sub is playing. The closer the notes are to the tuning frequency, the greater the reinforcement — the "boom" that people describe. Below the tuning frequency, the sub’s output drops off more dramatically than it does in a sealed box, so the lower a box’s tuning frequency is (and most are in the 30s), the deeper a sub in a ported box will comfortably play.

Ported boxes are popular with fans of rock, who like the chest-punch of the kick drum that efficient ported subs can provide, and of rap, hip-hop, and electronic dance music, for whom the low-end reinforcement adds the resonance they crave.

The sound curves of sealed and ported boxes

Using pink noise, we tested two 12" JL Audio subs in the Crutchfield Labs: one in a sealed box, the other in a ported. The sub in the sealed box showed a natural response that was smooth and linear. The ported box played efficiently and, thanks to its 34Hz tuning frequency, reinforced the sub's output in the lower end.

Which one is for me?

For many, the choice between sealed and ported boxes comes down to a combination of power, size, and output considerations.

  • A sealed box will be smaller than a comparable ported box, but require more power to achieve comparable output because of the strength of the air pressure inside the box.
  • Conversely, while ported boxes deliver greater output from comparable amounts of power, they tend to be larger and will take up more space in your cargo area.

[Shop for subwoofer enclosures]

As you’re shopping, you’ll also run across boxes called "bandpass enclosures." These remarkably efficient enclosures combine sealed and ported designs to deliver very high output over a specific band of low frequencies. To learn more about them, and get more info on sealed and ported boxes, check out our subwoofer enclosure article.

Power: more is better

The sound waves created by bass notes are big. Very big. And subwoofers require lots of power to generate them — the kind of power that only an external amplifier can provide.

When you’re looking for an amp to power your sub, there are two specs you’ll want to pay most attention to: the sub’s upper RMS power-handling spec, and the amp’s RMS output (RMS refers to the amount of power a speaker can continuously handle, or an amp can continuously put out; maximum power specs refer only to short bursts and are irrelevant for sub/amp matching).

Ideally, then, your amp’s RMS output wattage will be equal to or less than your sub’s top RMS power-handling specification. You can learn more in our article on matching subs and amps.

[Shop for subwoofer amplifiers]

Impedance: wiring multiple subs, or subs with dual voice coils

All electrical circuits and components, such as the voice coils of a subwoofer, offer some natural resistance to the flow of electricity. This resistance is called impedance, and is measured in ohms (and expressed with the Greek letter omega: Ω).

When you’re wiring your sub to your amp, you need to make sure that their impedance specs match (in the case of the amp, this is called being "stable" when presented with a particular impedance rating). For example, if you have a sub with an impedance rating of 2 ohms, you need to make sure your amp is 2-ohm stable.

DVC wiring technique

This diagram shows a sub with dual voice coils wired to present 4 ohms safely to a mono amplifier. You can learn more by checking out other subwoofer wiring diagrams.

It’s not unusual for audio enthusiasts to drive more than one sub with a single amplifier. There are ways to wire multiple subs so that the impedance they present to an amp matches the amp’s impedance stability specs. Similarly, some subwoofers feature two voice coils, which can be wired together to present an acceptable impedance to an amp.

The lower the impedance a sub presents to an amp, the more power the amp will send to the sub. That’s why it’s so important to make sure that you present an acceptable impedance to your amp: if the impedance is too low, the amp will overheat trying to supply more power than it’s capable of delivering. On the other hand, when you’re wiring multiple subs, or dual voice coils, presenting the smallest acceptable (safe) impedance to your amplifier is a great way to maximize power output and get the best possible subwoofer performance.

You can learn more in our article on wiring subwoofers, and by checking out some sample subwoofer wiring diagrams.

Low-pass and subsonic filters

Setting a low-pass filter

Low-pass filters keep high notes away from your sub, helping maximize its performance, and letting you blend its sound with your full-range speakers.

Just about every subwoofer amp on the market these days provides a low-pass filter. This helps ensure that only the low frequencies in your music reach your sub. The filter lets you choose the frequency at which it begins to block the high notes, which helps you blend your sub’s output naturally with the rest of your full-range speakers.

Setting your filter typically consists of lots of experimentation — there’s no one, right "formula" for where to set it.

  • You’ll want to make sure that your filter isn't set so high that the sub overlaps too much with the woofers of your full-range speakers, because this can result in overemphasis on one range of frequencies (say, around 120 Hz or so; think bass guitar and drums) and muddiness in your sound.
  • On the other hand, if you set your filter too low, you can leave a gap between your subwoofer output and your speaker output.

Try this: initially set your low-pass filter at 80 Hz, then listen. If it doesn’t seem quite right, adjust the filter up and down until it sounds the way you want it to.

Bass boost

Some people use bass boosts to increase the output at certain low frequencies.

Another good feature to look for in a subwoofer amp is a subsonic filter. These work by blocking super-low frequencies that naturally occur in some songs. You can’t actually hear these frequencies, since they exist below the threshold of human hearing, but if they’re not blocked, your subs will waste energy trying to play them. By blocking them, you free up your sub to play the notes that you can hear more efficiently, which gives you a more satisfying experience.

Bass boosts

Many amps also offer bass boosts, which increase the output of your sub at targeted, specific frequencies. While some people like to engage boosts to get extra oomph in some songs, others tend to use them sparingly, if at all, in order to keep bass output in proportion with the rest of the system.

Blending it all together

The explanation above is just a quick look at how to get your amp and sub working together. For a more detailed look at how to get them sounding good and how to blend the bass from your subwoofer with the music from your speakers, read our article on tuning your subwoofer.

More questions? Call us

Bass is certainly a fun and exciting element of your music, but we understand that getting the best subwoofer setup in your vehicle can be a complex topic. Our advisors will be happy to walk you through the process, and help you find the stuff that’ll give you the experience you want.

  • Jon from Bacliff

    Posted on 3/9/2021

    I am buying a pair of subwoofers that by themselves in a ported box the manufacturer recommends 40Hz for tuning frequency, but the dual 10" box I am planning to get is tuned for 32Hz. Will I lose out? or have untapped potential? Will the bass sound not hit as clean? Just curious if there were any specific answers or ways to go from here

  • PeterGomes from bogura

    Posted on 5/19/2020

    What a great article share. A great contribution especially for someone looking forward to buying a car subwoofer, amplifier and enclosure. If anybody wants to install a new one, this is the most effective share, that will be very helpful for best choice. Thanks a lot for the post.

  • Maria lena from new york

    Posted on 4/24/2019

    Thank you for sharing the knowledge and the tips! It is very helpful and informative. Every people like the best shallow mount subwoofer. Because, This subwoofer is very amazing for all people.

  • Jason from Fairbanks ak

    Posted on 9/22/2018

    How do I tune the cabin airspace for the highest spl

    Commenter image

    Alexander Hrabe from Crutchfield

    on 9/24/2018

    Jason, if you're building a box, you'll have good luck adhering to the specs provided by your sub manufacturer. Otherwise, this is a good a resource when it comes to our tuning your sub(s).
  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 8/31/2017

    Josh, in an ideal installation, you will have already adjusted your sonic filters to route bass to your subs. In that case your sub control should be the best way to adjust your bass.

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 8/31/2017

    Preet, if it's boom you're after, set the subsonic filter to the lowest setting. Adjust based on your musical taste.

  • Preet from Hoshiarpur

    Posted on 8/27/2017

    hello sir i want to know that how to set subsonic filter of mono amp? I have a dvc 4ohm 2000 watt subwoofer with 420 rms. I wired this sub at 2 ohm with 2ohm stable amp. I just want to know that how to set the subsonic filter and get the louder and boomy bass.

  • Josh from Jacksonville

    Posted on 8/25/2017

    I was told i should have my factory radio bass all the way down so it dosent interfere with my subs in the the trunk. Is this true?

  • devilgirl from NewYork

    Posted on 5/27/2017

    way cool

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 3/28/2017

    Anthony, that's great to hear. Glad we could help!

  • Anthony Reyes from Montclair

    Posted on 3/27/2017

    I just want to say thank you for your articles, this one in particular. I am not very knowledgeable in car audio equipment, so I put my trust in my local stereo shop. While I did get a good deal on a full system install, I was not very happy with the sound. Although it was loud it was extremely unbalanced and overall just sounded bad. I was almost thinking of going back to the shop and asking for my money back. Instead I decided to educate myself on equipment and ways to solve my problems. While a lot of the articles I read were a little to advanced for me, your articles (and 1 YouTube video) were easy to follow and understand. I used your recommendations from this article specifically to try to dial in my system. WHOA!!!!! What a difference! After just one of starting from scratch, I was able to get my system sounding REALLY GOOD. I will be tweaking and readjusting to really learn my equipment and get the best out of it. Without your articles I would have been eternally unhappy. Thank you very much :)

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 1/31/2017

    Thanks for your comment, Thad. The explanation in this article is not intended to be a "face palmer" but rather an accessible explanation for those considering adding bass to their vehicle possibly for the first time. Both our advisors and our tech support team are available to customers who need more detail on any aspect of improving car audio -- just give us a call.

  • Thad from Plano

    Posted on 1/30/2017

    Your description of how a 4th order enclosure works is embarrassing. Many people must have pointed this out already, this face palmer of an explanation. Is there no one at Crutchfield that knows how enclosures work, at least more than "the cone moves and makes a note", lol. You could just say; there is a resonant relationship between the spring-loaded mass of the cone and the spring-loaded mass of the port that when tuned correctly causes 180-degree shift at the tuning frequency between the front of the cone and the rear of the port and vice versa per whatever side of the wave the speaker is on, 90° or 270° increasing the amount of air you can compress into the enclosure. The more air volume you can compress is that much more air you can move, low frequencies are all about how much air you can move. Your Response graph is quite funny also. Not so much the data (which is wrong also as 4th order roll off is 24db and 2nd order is 12db) but that there are only 7 points of data in the top line. Did you graph it with 386, lol? Low frequency waves are long, not big, lol. Big is amplitude not frequency.

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 11/3/2016

    Frank, it sounds like checking your wiring would be worthwhile. Also, keep in mind that if you bought your gear from Crutchfield, you can call Tech Support for free help troubleshooting your system. If you purchased your equipment elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Check out our tech support page for details.

  • Frank from Manhiem

    Posted on 11/1/2016

    Hey I'm having trouble diagnosing this problem. When I open my trunk I get continuance bass, not even bass from the music. I'm thinking it's the ground or something I may have wired incorrectly... any ideas? I have a 2016 Altima running a 1200 watt amp with 2 15" subs... factory radio.

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 8/22/2016

    Leo, you'll want to check the manual for the ideal dimensions for both subs. You may even want to consult the manufacturer's tech support before beginning. And be sure to take accurate measurements of the space you'd like to use in your vehicle. Good luck!

  • leo from LEEUWARDEN

    Posted on 8/21/2016

    hello, i want to put a 12 inch sub end a 10 inch in the same custom box cause of limited room. will this work fine.

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 7/21/2016

    Pratik, I'd consider driving your sub with a separate mono amp and dedicate your 4-channel amp to driving your front and rear speakers.

  • Pratik Donde from Mumbai, India

    Posted on 7/20/2016

    Hi!! I have a Renault Duster with edition, which has built in head unit known as Media Nav and stock speakers, in door.. To enhance the sound ( As I am Soft Bass lover) I installed Rockford Fosgate Prime series 10" Sealed enclosure which I powered with JBL GX-A644SI - 4 Channel Power Amplifier to get the better output (it was the best available in my budget) Now, My sub has 200 Watts with 4 Ohms and my amp is 1000 watts 4 channel AB type I have taken HU's rear L/R channels to give input to AMP, Duplicated signals using RCA to provide 4 channel input to AMP, I then used AMP's Rear channel for Sub and front for my rear door speakers (just to mention, rear door speaker output was unbelievable after this) everything looked good from my side but, I am not able to get the expected output from my speakers, my sub does not provide crisp sound as I expected, I have tried LPF tried gain tuning with Test tones of 40 hz tried to tune frequencies, now I feel very nervous as I am unable to find where I am getting wrong. Can you help me out!

  • clicchi from Chicago

    Posted on 5/16/2016

    I think that bass bins in cars should be banned completely. The effect of bass is felt and heard even through walls over a mile away. There should be a way to generate bass in a car that stays in the car and not polluting the sound environment and ruining quality of life for those up to hundreds of yards away from you and your noise. My kitchen walls vibrate from auto bass bins that are a half mile away. It's insane and invasive. Where does one person's freedom to make noise trump anther's right to peace and privacy?

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 4/28/2016

    Pavan, check the manual for the ideal dimensions for your subwoofer or you may even want to consult the manufacturer's tech support before beginning. Be sure to take accurate measurements of the space you'd like to use in your vehicle as well, then follow the steps outlined in this article. Good luck!

  • pavan from sivasagar

    Posted on 4/28/2016

    Hi i have a 12'' 150 watt woofer and i want to make a bass tube with it, but don't know about the correct thickness correct diameeter and hight of pipe. plz help

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 4/27/2016

    Angel, check out the link under the "Blending it all together" header. It will send you to this article in which we discuss gain.

  • Angel from DETROIT

    Posted on 4/26/2016

    Great article however you never explained how to set the gain so that the subwoofers won't be louder than the other speakers or too low

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 3/24/2016

    Quinn, your best bet is to contact your sub manufacturer for the ideal specs for your particular sub. This will give you a sense of the ideal requirements for great performance. Other than that, trust your ears. If you're happy with the resulting bass, then your work is done.

  • Quinn Leadbetter from West Monroe

    Posted on 3/23/2016

    I'm buying a box to go underneath my seats in my truck and the mounting depth of the box is 5.5" and the mounting depth of the subs are 5" will that work and will the sound quality be good since the bottom of subs are so close to the bottom of the box.

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 2/15/2016

    Eli, your best bet would be to contact Memphis customer support. They may be familiar with your problem. Also, you can get expert Crutchfield Tech Support - 90 days-worth for only $30. Check out our tech support page for details.

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 2/15/2016

    Fred, check your crossovers, especially those in your receiver and/or amp powering the speakers. Everything might accidentally be set for low-pass. Otherwise, if you bought your gear from Crutchfield, you can call Tech Support for free help troubleshooting your system. If you purchased your equipment elsewhere, you can still get expert Crutchfield Tech Support - 90 days-worth for only $30. Check out our tech support page for details.

  • Eli roberts from Monticello ky

    Posted on 2/14/2016

    I have a ddaudio 2500series 12" sub that is 400-800 watts rms and the burst power is 3200watts its in a Atrend ported box and I'm using a Memphis 750.1 amp sub is wired at 2ohms and for some reason the sub keeps bottoming out I think there is something wrong with the amp because this is not the first time it has done this to a sub before but I was also told it could be the box I've switched boxes and still dose the same thing need help please

  • Fred

    Posted on 2/12/2016

    What if my full range speakers aren't picking up the high hz? I have two 12"s and a amp. With aftermarket kicker full range speakers

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 12/14/2015

    Abel, there are a number of sites dedicated to sub enclosure building that feature widgets that might be able to help you with the exact dimensions you need. Worth an internet search. Also, keep in mind, that if you already have your sub, the manufacturer will provide you with the measurements you need to get optimum bass.

  • Abel from Arlington

    Posted on 12/11/2015

    Would a low tuned ported enclosure have to be much bigger In size than a higher tuned enclosure? I'm thinking for example 26hz compared to 35hz?

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 7/10/2015

    Tray, the numbers you cited point toward you having more than enough power. If it's possible, you might try powering the system directly from your car battery rather than the HC 800 to see if there's an audible difference in the output. Alternatively, if the "quiet" problem isn't extreme, maybe a repositioning of the subs could help too.

  • Tray from Warsaw, Indiana

    Posted on 7/9/2015

    I have 2 12 inch Pioneer SVC rated at 300 watts RMS. I wired them together at 2 ohms for my power acoustik amp pushing 1400 W at 2 ohms. its a Monoblock amplifier. I am running them from the battery in the car to an HC 800 battery in the trunk to reduce light dimming. I feel like my subs for some reason are getting quieter and not hitting hard at all. Is there anyway I can fix this?

  • Commenter image

    Robert Ferency-Viars from Crutchfield

    Posted on 6/23/2015

    Austin, first off, if you purchased your gear from Crutchfield, give us a call and our Tech Support team will be happy to help. If you purchased elsewhere, then check out this guide to tuning your subwoofers. It's a great place to start and will help you balance the subs in no time.

  • austin from 98801

    Posted on 6/21/2015

    how do i tune a sub woofer to be prominent, but not overpower the music. i just got a whole alpine system, alpine components up front with pillar tweeters, and co axils in the rear with a 350 watt alpine 5 channel. now how to do i tune the subwoofer. (kicker 10 comp at 4ohm 150 rms being powered at 250watt rms in specific ported box. where do i start?

  • Commenter image

    Alexander Hrabe from Crutchfield

    Posted on 6/9/2015

    Mickey, a match between your subs and amp will also depend on the subs' impedance and number of voice coils in each. This article should help you with that. Regarding the enclosure, you're above the minimum requirements you cite, so you should be fine. Since it sounds like you already have all the components, put them together and give it a try. Personal preference will be the ultimate decider. If it sounds good to you, then it's right.

  • MICKEY from W.V

    Posted on 6/8/2015