Subwoofer box: How to choose one

Subwoofer box

A subwoofer is a speaker unit that requires a right enclosure unit known as the subwoofer box. In order to get the best bass sound quality and audio experience, the right choice of subwoofer box is what you need to sort after. There are various categories of subwoofer boxes that you need to know which will be discussed in this article before walking into a shop and purchasing one. The main categories of subwoofer boxes are ported, sealed and bandpass boxes. A car owner should ensure that they purchase the best subwoofer box choice which should be professionally designed and crafted to avoid compromise on audio quality.

Ported subwoofer boxes

First in the category, the ported subwoofer box which is the most popular subwoofer box. A ported subwoofer, also known as a “vented box” comprises a box with a port. The port is tuned to a specific frequency which makes it reinforced to low bass response hence making it the most efficient subwoofer box in the market today. Ported boxes allow maximum volumes of music to be reached as well as that sonic boom of bass to be produced. That forceful bass is produced since the enclosure allows more output as compared to sealed boxes which require high wattage amplifiers for greater sound reproduction.

Ported subwoofer boxes require a bigger enclosure as compared to sealed boxes. The advantage being that it can be used to produce more sonic, deep bass by use of a subwoofer of a similar characteristic. The design of this box allows back waves to reach the listener’s ears as well as the front waves. This makes them produce more sound output. Port design allows the ports to produce sound to a tuned frequency but if the power handling is below the tuned frequency, thus poor, it will compromise the subwoofer speaker hence susceptible to damage.

These ported subwoofer enclosure boxes do not provide internal pressure against the subwoofer where the cone is free for movement. Reasons for ported subwoofers to have a loud and deep base is caused by the air flow in and out of the port which create an audio effect similar to whistling. The tone strengthens and adds to the note the cone plays. Ported boxes are preferred for hard-driving music like rock and heavy metal. The only downfall of a vented subwoofer box is that they are less accurate as compared to a sealed subwoofer box.

Sealed Subwoofer boxes

The second category is the sealed subwoofer boxes. These types of boxes are popular for quality bass production. They are small in size as compared to ported subwoofer boxes hence can fit in different car sizes. They deliver a punchy deep bass, hence the best subwoofer box design for deep bass, not thunderous bass. All bass notes are accurately produced where the air retained in the box acts as a shock absorber to the subwoofer cone. This cushions the cone during its back-and-forth motion therefore all notes are produced accurately, hence an increase in transient force.

Sealed subwoofer boxes have excellent power handling capabilities where the subwoofer speaker cannot undergo excursion beyond peak excursion commonly referred to as “bottom out”. A sealed subwoofer has a low frequency response and tends to play tight full bass that provides a low level frequency foundation to the music played. The air being held into the box has several negative impacts on the subwoofer speaker. The main one being heat produced by the cone does not escape due to the trapped air by the seal which may affect the performance of the speaker. Due to the limited displacement of the cone, the subwoofer is less efficient, hence less sound production.

Bandpass subwoofer boxes

The last variant of the subwoofer box is the bandpass box. This is an unpopular subwoofer type that raises a lot of questions amongst car subwoofer buyers. This is a specially designed type of ported box design for maximum bass output and slam. The subwoofer speaker component is inserted into the box where the cone faces the sealed part of the box while the face of the speaker faces towards the ported side of the subwoofer box. Sound waves emerge from the ported side of the subwoofer enclosure where it is extra loud and within a narrow frequency range.

This subwoofer box combines the two technologies of ported and sealed subwoofer boxes. This makes the speaker loud and booming hard. Bandpass subwoofer box designs are the loudest subwoofer box designs in the car audio market. The bandpass subwoofer boxes are easily suited for their aggressive nature in loud bass sound reproduction. The music they work best on is reggae, rap and hard rock. They have off the chat power handling and excellent low frequency response. These types of subwoofer boxes pose a big challenge when it comes to tuning them to suit the consumer needs and speaker specifications. This poses a need to buyers to ensure that they purchase a subwoofer box specifically made for the subwoofer to ensure optimum performance.

Bandpass subwoofer boxes have an untuned port to suit speaker requirements therefore a ported or sealed subwoofer box might be the best option if you want to build the box by yourself. It is therefore recommendable to buy a subwoofer box unit that is already pre built and assembled in a factory since you will be guaranteed that the speaker and the box will work together without further or additional adjustments.

There are some other two rarely categorised subwoofer boxes that are the stealth box and the free air subwoofers. These are subwoofer boxes’ designers that have come up with these terminologies.

Stealth subwoofer boxes

The stealth boxes are meant for vehicle specific dimensions where they are ordered depending on your ideas or specification of the car space which is communicated earlier to the subwoofer box designer. This makes the subwoofer box incorporated into your car with regards to its physical space and interior design. They also include bass forms which are custom made up of fiber glass because of its light weight and long-lasting properties. This saves on dead weight and car interior space. These boxes are the strongest and the most lightweight subwoofer boxes available in the market today.

Free air subwoofer or infinite baffles

Free air subwoofers, also called infinite baffles, consist of woofers mounted to a board attached to the rear car deck or placed in the trunk against the rear seat. In this setup, the car boot space acts as an enclosure space where the speaker sound is isolated from the back of the speaker hence solving the sound cancellation problem of subwoofers without enclosures. This type of arrangement saves on space but the subwoofer must be designed for use in a free air environment hence specifically designed for free-air use. Flat frequency cancellation response is effective on this setup and also their installation is easy but has a drawback in power handling levels that subwoofer box counterparts.

Other factors to consider while choosing a subwoofer box

Other factors that a car owner should put into consideration include: materials used in constructing the subwoofer box, accessories required to assemble a subwoofer box and the fixation methodology. There are various materials used in the manufacture of subwoofer boxes which highly influence the performance and longevity of the subwoofer unit. The materials commonly used are medium density fibre (MDF) boards, fibreglass, plywood, pine wood, standard wood, sonotube and polycarbonate. We will give a brief description of the above stated materials so that you can see how and which is the best.

Medium density fibreboard is a standard material which is the most popular construction material due to its availability. It is durable and made up of dense and thick manufactured wood which prevents resonance and sound distortion. The con of having a subwoofer box constructed with medium density fibreboards is that it tends to get heavy hence requires more effort to move around and increases the car’s dead weight. Pine wood, plywood and standard wood are good alternatives for MDFs where the difference comes from sound quality.

Fibreglass is light in weight and highly customisable to suit customer tastes and preferences. The material is easy to work with but its drawback is that it is not suitable for large single panels. It also needs professional hands to work around with since it is a high-end installation material. Sonotube is the best for cylindrical subwoofer box construction. It is used in the concrete making where it is a thick and sturdy cardboard tube. It can be combined with MDF or plywood to be the top or bottom material for the tube.

Polycarbonate material is used to manufacture transparent subwoofer boxes. This material is flexible hence it can sustain the air force produced by a subwoofer even at full blast. Polycarbonate is used where aesthetics is put into consideration or top priority.

Accessories required to fix a subwoofer box

Accessories are required to fix a subwoofer box into a car and all components required are top priority hence a car owner or a subwoofer installer needs a subwoofer box calculator methodology. This will facilitate the managing space and efficiency of the unit. Some installers put the amplifier into the box which should be well fixed to allow proper functioning of the subwoofer. This gets technical hence professional advice should be sought by a buyer hence a better recommendation would be an out of the shelf subwoofer box because everything has been tested and assembled by the manufacturer.

8-inch to 12-inch subwoofers are the most common to find in the car audio market. Therefore, choosing the right enclosure for your subwoofer is a critical decision-making process. Example a subwoofer box design for a 12-inch subwoofer speaker, all the components sourced should match it so as to avoid compromise to the sound system. This is achieved by sourcing the best audio components of the best specifications in the market.

When it comes to how to build a subwoofer box, this exercise will depend on whether you are a skilled subwoofer box designer or you just want to try out a talent or a hobby. All you will need is some basics and materials. This will be a fun a moment and also it can save on cash which can be invested in other audio components.

The basic steps include determining the minimum depth of the subwoofer box where you measure the depth of the subwoofer that is the front to back dimension of the box and add two inches. This should be the total depth of the subwoofer box. The next step is to measure out the dimensions of the height and width of the box. Additional space should be provided if the owner plans on adding a protective grill. Then the subwoofer box designer should determine available car space and sketch out the box. Determine the interior box dimensions and adjust to suit the subwoofer specifications. Create passages for the cables and if an amplifier is being added to the setup, also create space for it. The final task is ensuring that the subwoofer box is well finished to the owners’ personal taste and liking.


Once all the above-stated details are followed in this article, a car owner can comfortably come up with the best subwoofer box of choice. It is a great and soothing experience to obtain a subwoofer box of choice where you will always be confident to listen to music as you cruise the roads with friends and family. Enclosed powered subwoofers are the best when it comes to subwoofer choice but nothing can match passive subwoofers paired with the right audio devices and gadgetry.

Noting that all subwoofer boxes are well designed and built for deep and loud bass production, at times it narrows down to consumer preference and tastes. These are also influenced by the type of music played, types of subwoofer speaker units and the amplifier classes or types. If you need to get things separately, then you should have a great understanding of how they function and sound. To conclude, sealed, ported and bandpass subwoofer boxes are the most popular in the car audio market, followed by smaller players such as stealth boxes and free air subwoofers.


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