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Best Free Air Subwoofers

Using a free air subwoofer is great for applications where trunk space is at a minimum. It’s usually the easiest and least expensive way to add some bass to your ride without giving up your precious trunk space for a giant subwoofer enclosure. But with so many great subwoofers to choose from, how do you know which ones are the most suitable for air use?

Luckily, We’ve done the heavy lifting for you. We’ve put together this resource – a one-stop-shop, all-inclusive guide to help you make an informed buying decision and find the best free air subs that fit your vehicle.

What is a Free Air Subwoofer?

To put it simply, a free air subwoofer, as its name suggests, is a specially designed speaker that’s built to work efficiently without being mounted in a box, or let’s say it’s designed to be installed on any kind of baffle with an air space behind it, such as a car trunk.

Unlike regular subwoofers, free air subs have specially designed suspensions that let them work without a real enclosure and make them perfect for lower-volume systems.

Best Free Air Subwoofers Reviews

1. Kicker 10C104

Kicker 10C104 Free Air subwoofer Review

Specifications of Kicker 10C104
Size 10″
Impedance 4 ohms
Dual Voice Coil No
Sensitivity 86.2 dB at 1 watt
Frequency Response 30 – 500 Hz
Power Handling (RMS/Peak) 150/300 Watts
Top Mount Depth (inches) 5″

Kicker is another well-established brand in the car audio industry. They’ve been in business for a very long time and have mastered the art of making quality car audio products for a reasonable price.

Kicker offers everything from car speakers and subwoofers to car amplifiers and signal audio processors. Most of their car subwoofers are designed to be as universal as possible. Therefore, they can be mounted in sealed or vented boxes as well as on an Infinite Baffle (free air).

The 10C104 is one of the best free air subwoofers in the Kicker Comp series. This 10 inch subwoofer is built to give you all the hard-hitting bass you could want in a sub without spending a ton of cash.

This woofer is built on tough steel basket which provides a reliable foundation for big bass. It features a thick injection-molded polypropylene cone with ribbed foam surround. The ribbed foam surround offers long excursion and keeps the cone on target, while the double stitching ensures your sub won’t come apart at the seams.

This versatile sub sports a strong motor structure with extensive venting to ensure long-lasting performance. Its 4-ohm impedance makes it compatible with just about every amplifier on the market.

Our main complaint about this subwoofer is that it can only handle 150 watts RMS and has a relatively weak sensitivity rating (86.2 dB). Depending on your setup, this sub might not give you enclosed sub levels of bass. Nevertheless, it’s still a decent subwoofer for the price.

2. JBL S3-1224

JBL S3-1224

  • Polypropylene cone
  • Nitrile rubber surround
  • Stamped steel vented basket
  • SSI (Selectable Smart Impedance)
  • Premium screw-down terminals
  • Oversized 3.0 inch Aero-cooled voice Coil
  • Premium 8 AWG screw-down terminals

Last update on 2021-05-07 / Affiliate links / Images from Amazon Product Advertising API

Specifications of JBL S3-1224
Size 12″
Impedance 2 ohms
Dual Voice Coil No
Sensitivity 92 dB at 2.83 volts
Frequency Response 25 – 175 Hz
Power Handling (RMS/Peak) 500/1500 Watts
Top Mount Depth (inches) 7″-1/16″

JBL is one of the most trusted names in the loudspeaker industry. The company has been in business for a very long time and have mastered the art of making quality. They’ve released everything from home audio systems to headphones and maintained a level of quality throughout. The same goes for their their selection of car speakers and subwoofers.

The S3-1224 is one of the best free air subwoofers that JBL has to offer. It’s 12-Inch in size, and it can handle a decent amount of power on continuous basis.

The JBL S3-1224 is rated for a sensitivity rating of 92 dB, and can handle up to 500 watts RMS. It has a frequency response of 25Hz – 175Hz and is suitable for both sealed and ported enclosures, as well as free-air use.

This JBL 12 inch sub is incorporated with an oversized three-inch (75mm) voice coil, allowing the subwoofer to be relatively lightweight compared to subwoofers with four-inch voice coils, and capable of handling more power than conventional two-inch voice coils. This strikes the perfect balance between thermal power handling and low mass.

Speaking of thermal management, this JBL free air subwoofer sports an advanced aero-cooled voice coil design which ensures long term reliability and consistent performance.

What sets this 12 inch free air subwoofer apart from other subwoofers in the market is the SSI (Selectable Smart Impedance) technology that it’s featured with. SSI lets you select the optimum impedance —2 or 4 ohms— by simply flipping a small switch. This allows for greater flexibility and a variety of system configurations.

All in all, if you’re looking for a reasonably priced free air subwoofer with more power, more reliability, more flexibility — and no compromises, then JBL S3-1224 is for you.

3. Kicker CompRT 43CWRT672

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Kicker CompRT 43CWRT672

  • Injection-molded polypropylene cone
  • Tough Santoprene surround with interlocking front gasket
  • Dual pair of spring-loaded wire terminals
  • Double venting for max cooling
  • High-temp voice coil for increased power handling

Last update on 2021-05-07 / Affiliate links / Images from Amazon Product Advertising API

Specifications of Kicker CompRT 43CWRT672
Size 6 3/4 -inch
Impedance 1 ohm or 4 ohms
Dual Voice Coil Yes
Sensitivity 82.57 dB at 1 watt
Frequency Response 30 – 500 Hz
Power Handling (RMS/Peak) 150/300 Watts
Top Mount Depth (inches) 2″-3/4″

This is another great free air sub from Kicker, except this time the subwoofer at hand is on the small size. That’s not to say that it’s lacking in terms of performance. Quite honestly, the subwoofer at hand is designed to perform just like a full-size sub, but without killing all your cargo space.

Kicker CompRT 43CWRT672 is a 6-3/4″ subwoofer with dual 2-ohm voice coils. It stands at less than 3″ tall, so your installation options are wide open. It could be an excellent replacement to a factory installed subwoofer (a little trimming might be required).

This subwoofer is featured with a rigid injection-molded polypropylene cone that won’t flex and cause distortion while you’re cranking the bass. Its cone is supported with heavy duty Santoprene rubber surround to ensure it’s centered, and to allow for long-lasting performance that won’t break down when the bass gets heavy.

if properly powered, this small sub can make a night and day difference in terms of bass and sound quality. Speaking of power, the subwoofer at hand can handle up to 150 watts RMS so make sure you’ve got a solid amp to power. Furthermore, this sub can hit as low as 30Hz which is quite good for a subwoofer this size.

As far as wiring is concerned, you can wire the dual voice coils for either 4- or 1-ohm total impedance, giving you more flexibility when setting up your system.

In addition to being compatible with free air setups, this subwoofer also sounds great in a sealed enclosure.

4. Kicker CompRT 43CWRT102

Kicker CompRT 43CWRT102

  • Injection-molded polypropylene cone
  • Tough Santoprene surround with interlocking front gasket
  • Dual pair of spring-loaded wire terminals
  • Double venting for max cooling
  • High-temp voice coil for increased power handling

Last update on 2021-04-08 / Affiliate links / Images from Amazon Product Advertising API

Specifications of Kicker CompRT 43CWRT102
Size 10″
Impedance 2 ohms
Dual Voice Coil Yes
Sensitivity 84.8 dB at 1 watt
Frequency Response 25 – 500 Hz
Power Handling (RMS/Peak) 400/800 Watts
Top Mount Depth (inches) 3″-7/16″

The phrase “bigger is better” can be very hit or miss depending on what you’re talking about. When it comes to subwoofers, it can become even more inconsistent. That said, the phrase rings true when it comes to the Kicker CompRT 43CWRT102.

The CompRT 43CWRT102  delivers a bigger and better version of the CompRT 43CWRT672 subwoofer (listed above). The motor structure and the internal components are just as durable, making it ideal for serious bassheads. The power handling is bumped up to 400 watts RMS for better performance. However, the biggest improvement is in the frequency range. I mean this subwoofer can handle low frequencies beautifully and brilliantly as it can hit as low as 25Hz.

The dual voice coil subwoofer at hand can be wired for either 4- or 1-ohm total impedance, giving you more wiring options when setting up your system. Further, this sub can mounted in sealed or ported enclosures. It’s also suitable for free air use applications.

5. Infinity Kappa 1200W

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Infinity Kappa 1200W

  • Acoustically damped glass-fiber cone with rubber surround
  • Steel basket
  • Proprietary aero-cooling design keeps the voice coil cool
  • Premium screw down terminals
  • Selectable Smart Impedance (SSI)

Last update on 2021-05-06 / Affiliate links / Images from Amazon Product Advertising API

Specifications of Infinity Kappa 1200W
Size 12″
Impedance Selectable 2- or 4-ohm impedance
Dual Voice Coil No
Sensitivity 91 dB at 2.83 volts
Frequency Response 23 – 400 Hz
Power Handling (RMS/Peak) 500/2000 Watts
Top Mount Depth (inches) 7″-1/16″

Within the audio space, Infinity is one of the oldest and trusted names. They’ve been in business since 1968. The company has released everything from home audio systems to car audio components and maintained a level of quality throughout.

Infinity subwoofers have always distinguished themselves clearly from the competition. The Infinity Kappa 1200W subwoofer is no exception. It’s one of best 12 inch subwoofers that Infinity has to offer.

The subwoofer at hand is fitted with an acoustically damped glass-fiber cone for exceptional accuracy and detail. Due to its non-resonant nature, the glass-fiber cones eliminates distortion so your bass comes through loud and clear.

Once you get past the cultured exterior, the interior components uphold Infinity’s affinity for advanced technology.  This subwoofer sports Selectable Smart Impedance (SSI) technology which lets you build exactly the system you want without complicated wiring. It allows the subwoofer to run at 2 Ohms or 4 Ohms with the flick of a switch.

That said, If you’re thinking about upgrading your car audio system down the line, this sub makes it easy to reconfigure — and it’s nearly impossible to wire incorrectly.

The Infinity Kappa 1200W subwoofer is fitted with a steel basket with voice coil vents. This basket provides a solid base for the sub, which can handle a staggering 500 watts RMS of power. Furthermore, this sub can hit as low as 23Hz which translates to well-detailed and refined bass.

In addition to being suitable for free-air applications, this versatile sub also works quite well in sealed or ported enclosures.

6. Pioneer TS-SW2002D2

Pioneer Free air shallow mount subwoofer

Specifications of Pioneer TS-SW2002D2
Size 8″
Impedance 1 ohm or 4 ohms
Dual Voice Coil Yes
Sensitivity 86 dB at 1 watt
Frequency Response 20 – 200 Hz
Power Handling (RMS/Peak) 150/600 Watts
Top Mount Depth (inches) 2″-11/16″

A brand that pioneers in the car audio industry is worth the trust you’d put in a product that carries its logo; Pioneer is one of the top rated car stereo brands in the audio space. They’re as old as history, and none have set the standard the way Pioneer has.

The company has released everything from home audio systems to headphones and maintained a level of quality throughout. The same goes for its selection of car subs.

The TS-SW2002D2 is one of the best 8 inch shallow mount subwoofers out there. This 8 inch sub has 2-5/8″ mounting depth which is  less than half a typical subwoofer in this class. It’s designed to bring great bass to vehicles where traditional subs won’t fit. If mounted in a sealed box, this sub will neatly fit in under the seats of your vehicle.

The TS-SW2002D2 is featured with dual 2-ohm voice coils so you can wire it for 1- or 4-ohm impedance. It has an oversized cone made of mica-injected molded resin that moves more air and delivers accurate bass.

In addition to being a great sub for free air setups, the sub at hand works equally well in small sealed enclosure, making it ideal for those tight spaces in today’s smaller vehicles.

As far as power handling is concerned, the subwoofer at hand can handle up to 150 Watts RMS. It can reach as low as 20 Hz, which quite impressive for a subwoofer this size. Nevertheless, this subwoofer won’t shake the neighborhood by any means, so if you’re a serious basshead, you might want to invest in bigger subwoofer or in a couple of medium sized subs for better results.

7. Alpine SWR-M100

Alpine SWR-M100

  • Injection molded polypropylene woofer
  • High Amplitude Multi-Roll (HAMR) surround
  • Marine-grade Nomex® spider
  • High-strength polypropylene frame and waterproof rubber mounting gasket
  • High excursion for deep high output bass
  • Thermal management system
  • Integrated insert and spade terminals
  • 4-Layer single 4 ohm copper wire on TIL former voice coil

Last update on 2021-05-07 / Affiliate links / Images from Amazon Product Advertising API

Specifications of Alpine SWR-M100
Size 10″
Impedance 4 ohms
Dual Voice Coil No
Sensitivity 86 dB at 1 watt
Frequency Response NA
Power Handling (RMS/Peak) 300/900 Watts
Top Mount Depth (inches) 5″-1/16″

Taking a boat out on the water for the day with family or friends is one of the best ways to get away from it all. That said, no one can deny that music is the ideal complement to the sound of the wind and the waves whilst sailing or motoring along. But what if your boat audio system sounds muddy and muffled?

Well, Adding a subwoofer to your boat audio can make a significant difference in your overall sound quality. A subwoofer doesn’t merely extend bass response, but it also provides a sense of scale and dynamics superior to the speakers on their own. This even applies to music that doesn’t have a lot of obvious bass content.

What we have here is one of the best marine subwoofers on the market. The Alpine SWR-M100 is designed to help you take your next boating or fishing experience up a notch. It’ll deliver classic Alpine punch for resonant bass you can hear and feel.

This marine free air subwoofer is engineered to to stand up to heat and humidity, so you’ll enjoy great bass, season after season. Speaking of durability, this sub is featured with a molded polypropylene cone bonded to durable Santoprene™ rubber surround for long lasting performance. It’s also sports an airflow management system and CRC motor structure to keep it running cool, even in the summer heat.

The Alpine SWR-M100 sub can handle up to 300 watts RMS from your marine amplifier. It’s designed to work in virtually any type of enclosure including a sealed or vented enclosure. It’s also suitable for free-air use (infinite baffle) for the widest application.

8. JL AUDIO 10W0V2-4

JL AUDIO 10W0V2-4

  • Polypropylene cone with foam surround
  • High-quality push terminals accept speaker wire up to 8 AWG
  • 4-Layer 2 inch voice coil
  • Elevated frame cooling
  • High linear excursion

Last update on 2021-05-07 / Affiliate links / Images from Amazon Product Advertising API

Specifications of JL AUDIO 10W0V2-4
Size 10″
Impedance 4 ohms
Dual Voice Coil No
Sensitivity 84.07 dB at 1 watt
Frequency Response 25 – 250 Hz
Power Handling (RMS/Peak) 300/600 Watts
Top Mount Depth (inches) 4″-15/16″

When it comes to car subwoofers, JL Audio is probably one of the most legendary. JL Audio was founded in 1975 and has made a name for itself as one of the most renowned brands in the audio industry.

They offer a wide range of car audio components including speakers, subwoofer, audio processors, amplifiers and accessories. They’re best known for their top-notch car subwoofers.

The 10W0V2-4 is one JL Audio’s best free air subwoofers. Being featured with cutting-edge technologies such as optimized motor system that promotes precise, linear cone movement, plus advanced cooling throughout the frame for rapid heat dissipation allow this free sub to deliver trademark JL performance.

Additionally, this 10 inch free air subwoofer sports a tough polypropylene cone that’s bonded to durable foam surround for controlled driver excursion. Speaking of which, the cone’s extra-long excursion capability allows it hit truly deep lows with minimal distortion, while the beefy 2-inch voice coil drives the woofer accurately for extraordinary power handling.

Speaking of power handling, this subwoofer can handle up to 300 watts RMS which is more than enough to fill your ride with solid, clean tight bass bass.

So, if you’re looking for stellar performance at an affordable price, JL Audio 10W0V2-4 is for you. It’s one of the top rated free air subwoofer at this price range.

9. Rockville W12K6D4 V2

Rockville W12K6D4 V2

  • Polypropylene (pp) dustcap
  • Fiber reinforced ultra stiff black non-pressed paper cone
  • Double stacked 100 oz high quality magnet
  • 2.5 inch 4-layer black aluminum voice coils
  • Cast aluminum basket with black sanded finish makes this sub very efficient
  • Thick foam surround provides incredible sound quality with minimal distortion
  • Red stitching cone reinforcement ensures long life

Last update on 2021-04-08 / Affiliate links / Images from Amazon Product Advertising API

Specifications of Rockville W12K6D4 V2
Size 12″
Impedance 4 ohms
Dual Voice Coil Yes
Sensitivity 85 dB
Frequency Response 27 – 1500 Hz
Power Handling (RMS/Peak) 600/1200 Watts
Top Mount Depth (inches) 5.75″

While Rockville might be one of the younger companies in the audio space, it has been able to carve out a place for itself as a viable competitor.

Rockville offers a wide variety of car subwoofers of different types and sizes; Their car subs are modestly priced for the most part. They are not the best sounding car subwoofers out there, however, they get the job done without breaking the bank.

The Rockville W12K6D4 V2 is one of the best 12 inch subs that Rockville has to offer. Despite being budget-friendly, this beast is well-built. It’s equipped with a cast aluminum basket with black sanded finish. This basket provides a solid base for the subwoofer as it can handle a staggering 600 Watts of power on continuous basis (RMS), and with great power comes great responsibility. That’s why this sub is just as adept at shaking the car as it is reproducing a pure booming bass you can feel as much as hear.

This Rockville sub is designed to hit extremely hard. It’s featured with an ultra stiff fiber reinforced paper cone bonded to thick foam surround for incredible and clean bass with minimal distortion.

The Rockville W12K6D4 V2 can work equally well in a sealed or ported enclosure. It’s also suitable for free air setups.

10. CT Sounds Tropo 12 Inch D2

CT Sounds Tropo 12 Inch D2

  • 2.5 inch voice coil
  • Y35 graded triple stacked ferrite magnet
  • Sturdy and stupendous basket frame

Last update on 2021-05-07 / Affiliate links / Images from Amazon Product Advertising API

Specifications of CT Sounds Tropo 12 Inch D2
Size 12″
Impedance 2 ohms
Dual Voice Coil Yes
Sensitivity 85.2 dB at 1 watt
Frequency Response
Power Handling (RMS/Peak) 600/1200 Watts
Top Mount Depth (inches) 6.4″

Despite being a new born (founded in 2008), CT sounds has a relatively rich history in car audio world, and it offers a compelling line up of car subwoofers that are competitively priced.

The Tropo 12″ Free Air D4 Subwoofer is one of the best free air subwoofer that CT Sounds have to offer. It’s jampacked with advanced technologies that allows it to offer stellar performance while keeping your wallet intact.

This 12″ inch sub is incorporated with Y35 graded triple stacked ferrite magnet, which in conjunction with it 3″ voice coils and a stupendous arm styled basket frame allow this subwoofer to deliver quality SPL performance.

Speaking of performance, this subwoofer sport SPL rating of 90.9 dB and can handle up to 450W RMS.

Can Any Sub Be Mounted “Free Air”?

infinite baffle mounting

A regular subwoofer can be used as a free air subwoofer, but it won’t deliver that kind of performance and bass output you’d normally get when you mount it in a suitable enclosure.

Both the efficiency and power handling of the subwoofer go down significantly when it’s run free air or infinite baffle. This is because free air subs get their damping from the suspension while regular subs get it from the air pressure within the box.

I mean, think about it, typical sealed and even ported enclosures damp the motion of the cone because of the air pressure within the enclosure. In a free-air setup, you don’t have that, so a normal sub’s excursion isn’t as well damped as it should be, and the over-excursion puts your subwoofer at risk. For this reason, most free air subs have a stiff suspension to help deal with that.

Free air subs require a lot more power to achieve the same power output of a sealed subwoofer. I mean, if you take two similar non free air subwoofers and mount one in free air setup and the other in a sealed enclosure, the former would take a lot more power to sound as close as possible as the latter.

All in all, free-air mounting (Infinite baffle) does limit the total output of the subwoofer and its power handling. That is why it is best to stick with a subwoofer that’s designed specifically for this type of mounting configuration.

If, for whatever reason, you decide to mount a regular subwoofer in a free air application, make sure you set your gains low, and choose an amplifier which has a subsonic filter to filter out or attenuate frequencies so low that your subwoofer cannot reproduce efficiently.

How Free Air Subwoofers Work?

Since free air subs don’t have an enclosure, they will not take up as much room in your vehicle and can be mounted (in some applications) where they may not even be seen at all.

Free air subwoofer - infinite baffle setup

In a free-air application, a subwoofer is mounted either in the rear deck or attached to a medium to high density fiberboard placed between the backseats of a car and the trunk. This board makes an airtight seal and turns the entire trunk into an enclosure (which is also known as Infinite Baffle).

Infinite baffle Back Seat InstallationNot having to build an enclosure/box for your subwoofer is an advantage; a big one. However, since free air subwoofers use the whole trunk as a box, the trunk has to be as sealed as possible from the cabin so that the sound waves from the rear of the speaker cannot reach the front of the speaker to cause cancellation. Thereby, your vehicle might require a new rear deck panel and/or vent to be constructed to accommodate these woofers.

P.S: These custom vents and panels could cost as much as a prefabricated or custom box. So, when someone says that adding a subwoofer the infinite baffle way is inexpensive, take that with a grain of salt.

 

Free air applications require a woofer with a beefier suspension for high power handling and one with better cone damping. This set-up will be relatively less efficient at accurately reproducing the lowest frequencies.

Further, more amplifier power will be required as compared to a regular sealed or ported box, but then again, you still have a full trunk.

All in all, a free air setup is a great solution for you if you want to add punch and presence to your music without sacrificing the entire cargo area on your vehicle.

Free Air Vs. Infinite Baffle 

Free Air Subwoofer“Is Infinite Baffle and Free-Air the same thing” is a common question that we frequently get asked. The answer is that they are not actually the same thing but are very much related.

In a nutshell, a free air sub is a speaker designed to sound well in the open air (hence free air) without the use of an enclosure. It’s built to be mounted in the rear deck of a car, for example, and still sound good.

Infinite baffle on the other hand can be as simple as a board or a mounting surface (called a “baffle”). This can be a flat MDF board with your free air sub(s) mounted to it and then attached to the back of the seats of a sedan.

Many vehicles out there have at least one subwoofer mounted in the rear package tray infinite baffle right next to the full range speakers.

With this type of mounting, the car trunk is typically used as an “enclosure”. However, It must be noted that when mounting your subwoofers in an infinite baffle configuration, you must have a woofer that is capable of operating in an infinite baffle.

Infinite Baffle SetupAdditionally, you need to make sure that you seal the mounting baffle as good as possible to prevent the rear waves of the speaker (generated from the back of the subwoofer cone) from cancelling out the front ones.

An ideal infinite baffle setup can be a serious challenge due to the potential difficulty of sealing off the back pressure waves of the subwoofer from its front pressure waves, because otherwise bass cancellation will occur.

It must be noted that bass can easily travel through anything that is not solid enough such as the rear seat foam or even the speakers mounted near the subwoofer. Therefore, any area that’s not sealed enough between the front and rear of the baffle will negatively impact bass quality.

Infinite Baffle : Pros & Cons

Pros

  • The infinite baffle system is very simple and easy to install
  • Simplified installation on a baffle board ( no full enclosure )
  • Smooth frequency response
  • Does not take up much room in trunk
  • Uses speakers’ natural frequency roll-off

Cons

  • Separating back waves from front waves is challenging
  • Limited power handling
  • Limited output
  • Requires an amplifier with subsonic filter (mandatory)
  • The trunk must be sealed from the cabin to prevent bass cancellation
  • Rear side of the driver is exposed along with the wiring and it may not be a clean looking installation

Infinite Baffle/Free Air Application Types

There are various ways to mount your subwoofer the infinite baffle way. All of these follow the same concept. Which to use is dictated by your vehicle. Any of these could work just fine in a a large sedan. However, some of these configurations might not work well in hatchbacks.

Typical Rear Deck Installation

If you have a large sedan, then you’re in luck because you’ll have enough surface area to accommodate a pair of 10 or 12 inch woofers.

These vehicles are the easiest to incorporate an infinite baffle set-up into. However, like with any free-air application, the trunk has to be as sealed as possible from the cabin.

This can accomplished by putting a thick medium to high density fiberboard under the deck to help hold the weight of the subwoofer and to keep it from flexing during playback.

To prevent the trunk, or rear, sound waves (generated from the back of the subwoofer cone) from entering the passenger area of the vehicle and cause cancellation, a thick particle board should be added behind the seats.

Back Seat Installation


As shown in the diagram, mounting your free air subwoofer behind the back seats instead of under the rear deck is another type of infinite Baffle.

This is often much easier and less expensive than cutting the rear deck and will not require a ton of modifications to the existing deck panel.

Small Deck Installation

The lack of the surface area needed to mount a large free air woofer in the rear deck is one of the most challenging things with many modern vehicles. However, you don’t have to feel left out if this is the case with your car because it is still possible to use free air woofers by venting them through the rear deck as shown in the the diagram.

Sealing the trunk area from the cabin is still critical to a successful installation.

P.S : Try to keep the inside dimensions of the front and rear walls of the vent at least four inches apart when working around trunk springs and other obstacles.

 

How to Install a Free Air Subwoofer

In this setup, we decided to make the baffle the full width and height of the back seat. We started by making a template out of cardboard.

After marking your baffle with the template, make sure to cut directly on the line. Once done, test fit it.

If the baffle fits perfectly, start cutting the speaker opening. A this point, there will be a lot of grinding and sanding to get the opening right.

For rigidity purposes, you’ll want to double up the baffle to keep it from flexing during playback.

For aesthetics purposes, you’ll want to finish the baffle. If you decide to carpet the baffle, it is important to cut the carpet around the woofer opening. It’ll be hard to get a good seal if you have both the gasket and the carpet between the woofer and the baffle.

Once the baffle is fully carpeted and finished, install the driver in it and mount it flush against the back seats. This gives the baffle some extra support and ensures that all of the front wave is funneled through the ski pass.

In this case, we didn’t have to seal the baffle as the back seat is already sealed nicely to the cabin. However, our major leak was in the rear deck, and for that we used Dynamat to close them off.

This how the  subwoofer looks like from the front

Free Air Subwoofer Installation – Tips

Tip #1 – Use a free air subwoofer

It goes without saying that only a free air subwoofer should be used in an infinite baffle / free air application. Otherwise, expect limited output and bass response.

Tip #2 – Make sure there’s no bass cancellation

The key factor when mounting a free air subwoofer in your car is to make sure the sound waves produced by the front and the back of the subwoofer don’t meet, so they don’t cancel out each other. If the front and back are not sealed from each other a big part of the bass will get cancelled out.

That said, to completely seal the trunk from the interior of the car, use a thick particle board behind the seats, seal all around the baffle, and make sure all gaps or holes in the trunk area are filled with silicone.

Finding where the rear sound waves are leaking into the cabin can be very difficult. The best way to identify that is a simple smoke leak test.

Tip #3 – Don’t push your subwoofer to the limits

Infinite baffle subwoofers can easily exceed their Xmax (also known as over-excursion) if pushed hard. Xmax refers to the distance a voice coil can move in one direction without leaving the magnetic zone.

Tip #4 – Reinforce the rear deck

If you’re mounting the subwoofer in the rear deck, make sure you mount a thick MDF (Medium Density Fiberboard) to the bottom of the deck to help hold the weight of the subwoofer and to keep it from flexing when bass gets heavy.

Tip #5 – Take boot  space into account

Mounting a small subwoofer the infinite baffle way in a large trunk will result in subpar performance due to the lack of air pressure in the trunk. So, always take boot space into consideration.

Vented, Sealed, Bandpass, or Free Air, Which is better?

Well, this is not an easy question to answer. Simply, because it depends on a ton of things including but not limited to your vehicle, the kind of bass you want, the compromises you’re willing to make, your overall sound setup …etc.

Infinite baffle or Free-Air

Infinite Baffle SetupTo put it simply, a subwoofer without an enclosure is in an infinite baffle configuration. The latter usually consists of a woofer mounted in a rear package tray or on a flat board (called a baffle board) that is attached to the back of the seats of a car.

As we mentioned above, a free air subwoofer is a basically a speaker that’s designed to operate in a very large sealed enclosure, such as a trunk, therefore, it’s safe to say that real world infinite baffle configurations are merely a particular case of sealed box.

I mean think about it, if you build a super large sealed box, the air inside it will not alter the compliance of the driver, and there you have it : infinite baffle.

infinite baffle frequency response curve

Pros

  • Relatively easy to construct
  • Smooth frequency response
  • Does not take up much room in trunk
  • Uses speakers’ natural frequency roll-off

Cons

  • Limited power handling
  • Limited output
  • Requires specific crossover tuning for best results.
  • Sealing off the back waves from the front ones can be challenging

Sealed Box

A sealed enclosure is exactly what it sounds like. A closed box that is air tight. In this type of enclosure, the air doesn’t escape the box. It acts like a limiting spring to help control the movement of the cone of the woofer.

Sealed enclosures are the easiest enclosures to design and build. They vary in size and shape – depending on the size of the subwoofer – and are considered one of the most accurate sounding enclosures when built properly. In a sealed box, the lower bass response will roll off at 12dB/octave.

Sealed enclosure frequency response curve

Sealed enclosures have very deep and smooth bass response, impressive power handling, and hard-hitting sound. This will all depend on how the box is constructed. If the air volume of the enclosure is too large for what the subwoofer manufacturer recommends, then the subwoofer will no longer behave as if it were in a sealed enclosure. It will sound and perform like an infinite baffle.

Pros

  • Easy to design and build
  • Great power handling
  • Very tight bass response
  • Smooth low frequency roll off
  • Work great for music that has more upper, punchy bass

Cons

  • Require more power to overcome the internal air pressure = Low efficiency.

Ported Box

Also referred to as “vented” or “bass reflex”, a ported enclosure is a box that has one or more ports (which is usually cylinder shaped) in the enclosure to allow the rear sound wave to couple with the front sound wave of the speaker for greater output. The port has a predefined dimensions. The latter are crucial as they set a certain resonant frequency.

In a ported enclosure, the lower bass response will roll off at 24dB/octave, which is twice as fast as a sealed enclosure.

Ported enclosure frequency response curve

Ported enclosures can play louder. So, it’s safe to say that they’re one of the loudest subwoofer box designs. Why? Simply, because in a vented box, the rear sound waves are allowed to couple with the front sound waves from the subwoofer, resulting in an increased output around the tuning frequency. This increase in bass response makes them a good choice hip hop, rap recordings, and all other applications where where more bass volume is required.

Unlike sealed enclosures, ported ones are supper efficient. What this means is that you can get more output from the same power of an amplifier than a sealed enclosure.

Pros

  • Great efficiency
  • Reduced distortion (speaker doesn’t need to move as far near resonance frequency)
  • Reduced distortion around vent tuning.
  • Driver can hit lower frequencies, outside its frequency response.

Cons

  • Not as good transient response as sealed
  • A bit more difficult to design and build compared to sealed
  • The “port” can become noisy at high volumes.
  • Steep roll-off of 24 db/ octave.

Bandpass Box

In a bandpass enclosure, the subwoofer is out of sight, because it’s mounted completely inside of the enclosure, and the sound comes out only through the port(s).

A bandpass enclosure consists of a single enclosure with a divider inside that will form two chambers. There are a few types of enclosures when it comes to bandpass (4th / 6th / 8th order bandpass).

In 4th order bandpass, one side of the speaker is placed in a sealed enclosure, while the other side is placed in a ported enclosure. A 6th order bandpass has both chambers ported, while 8th order bandpass has an additional ported chamber.

Bandpass enclosures are usually big, and very unforgiving when it comes to volumes and port sizes, which makes them quite difficult to build. Therefore, you must follow the manufacturer’s instructions to avoid speaker damage and failure.

Bandpass boxes usually deliver more bass than sealed and ported boxes (especially at lower frequencies), but only over a narrower frequency range.

Bandpass enclosure frequency response curve

Pros

  • Bandpass boxes are much harder to construct (because the woofer is totally inside the enclosure)
  • They’re extremely critical on the design, with no room for error
  • Good choice for high SPL applications

Cons

  • Enclosure can get impractically big
  • Tune it for efficiency, and get subpar sound quality
  • If pushed hard, you don’t hear the woofer “struggling” (as it is inside the cabinet) and might kill it unknowingly.

Final Thoughts

If you have a question about a free air subwoofer you’re considering — or want to pick my brain on anything in the article — leave a comment below. I’ll respond quickly, and if I don’t know the answer I’ll find someone on my team that does. Thanks for reading!

Alex Brown

Hey There, my name is Alex Brown, I'm an LA-based sound engineer with over 10 years experience installing, troubleshooting, and repairing commercial, automotive, and household sound equipment. I've installed highly competitive car audio systems, and everything from navigation systems to full car stereo systems, remote starters, alarms and beyond. I enjoy creating solutions and simplifying everyday needs. I also love helping people get great sounding gear, thereby, saving the world from bad sound one customer at a time.

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