Importance of cubic capacity for subwoofer

Subwoofer box enclosure: what is it, its importance and how to calculate the correct one

on December 19, 2022

Enjoying your favorite music in the car could become an extraordinary experience by installing a subwoofer. Buying it is just the first step for listening to great music in the car. The next step is the installation and calculation of the cubic capacity, for which you can follow the manufacturer's manual or instructions.

For a better understanding, today on the Genius Car Audio blog we will tell you what does subwoofer box enclosure means, how to calculate it and why it is important to follow this process. Let's get started!


What is a subwoofer enclosure?

Subwoofer box enclosure is a little complex. It's not just about getting the highest volume of air, it's also about finding the exact frequency of where you want the subwoofer to be at a "RF" resonant frequency point. This RF is the spot where the subwoofer´s resonance is adequate, and it is essential to spot it in the car in order to know where the subwoofer is going to be installed.

Usually, the manufacturer's manual gives us a clue of how many liters or cubic feet (ft3) will be indicated for the subwoofer´s work and will even advise where the subwoofer can be placed. However, vehicle models are different and have their own characteristics, so it will be essential to calculate the liters or cubic feet (ft3) that are specified in the manual which are expressed as Vb.

Measure the space you left to be used for the subwoofer box speakers or acoustic box  and save those measurements in centimeters or in inches to use later. Take the measurement of the bottom base (bottom depth) and the top base. In many cases, both measure the same, and in any case you will have to subtract the thickness of the two MDFs.

Correct subwoofer calculation

For example, when calculating the measurements of a box we will be using the unit of measurement in centimeters (cm) and we will have to take into account the thickness of the MDF that we are going to use; which in this case will be 1.9 cm. The external measurements of the box will have the following measures:

30 cm from the lower base and 20 cm from the upper base, 30 cm height and 55 cm length. Then we will have to subtract 3.8 cm from the thickness of the two MDFs in the lower base and another 3.8 cm from the bottom and then, the numbers that were gotten must be added and divided by two in order to obtain the average depth.

Following the previous example:

The height of the base is 30 cm, minus 3.8 cm of the MDF equals 26.2 cm. The length of the drawer is 55 cm minus 3.8 cm of the MDF equals 51.2 cm. Let's add: 26.2 + 16.2= 42.4 cm, and if we divide it by two it gives us an average depth of 21.2 cm.

Furthermore, if we multiply the average depth of 21.2 cm by the 51.2 cm length, it equals 28,438. Divided by a thousand, it equals 28,438, which indicates the liters of the box or enclosure. And if you want to convert this into cubic feet (ft3), the liters obtained are divided by 28,317, having in the example;  a 1-foot box.

The only thing missing, will be to increase or decrease the measurements in order to obtain the liters or cubic feet of the box for the installation of the subwoofer.


How to Calculate Net Internal Volume

When calculating the internal volume of the cabinet, you must subtract the volume of air displaced by the port, internal bracing, and subwoofer. That is: gross internal volume of the box (in cubic feet ft3) –subwoofer enclosure = net volume of the box.


Recommendations for best results

In order to have better results with the subwoofer installation, it is recommended to introduce an absorbent material, such as glass wool which is used in panels to soundproof spaces. These can help having a better reflection of the sound waves inside the vehicle and prevent too much noise from sounding outside.

An extra recommendation is to use wood glue and screws to fix the MDF to your vehicle instead of using cables, since the car´s movement or bumps on the road could cause interruptions in the sound.

How to calculate the correct displacement for subwoofer

In the case of very closed spaces, it is best to calculate sealed boxes that need fewer liters and are more flexible in terms of measurements. For example, a box of 15 to 20 liters can have a sealed speaker of between 24.1 and 49.5 liters.

Finally, we recommend that you always turn to professionals in order to achieve the results you are looking for. For both, to acquire your subwoofers, as well as for installation and technical support. You need the best to obtain the highest audio quality when you hit the road. Your car deserves it!

We hope this information is useful to you. We invite you to browse the Genius Audio online store to see the products we have for you: midrange speakers, drivers, car audio tweeters, installation cables, car audio coaxials, component kits, car amplifier, woofers, subwoofer for car, loudspeakers and much more.

For more information about our products, or if you are interested in being one of our distributors, write to us through the contact form or through the WhatsApp button where our staff will assist you and answer all your questions.


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