How to build subwoofer box to specifications?

How to build subwoofer box to specifications?

Johann a TV mounting Technician and Editor
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Last Updated on June 8, 2022 by Johann Holsinger

Finding or buying a premade subwoofer box is easy, but the easy option can look a bit bland and boring in your vehicle compared to building and designing something yourself with a bit of DIY expertise.

From my experience building, your own custom subwoofer box does take a little bit more effort but your results will blow for years of great times and enjoyment when driving or parking your vehicle up at the river.

This DIY project will give your car the best new look inside and create the best sound coming from your music.

Your custom-built subwoofer speaker box can also be made to fit into your car’s available space perfectly!

Flush in subwoofer

Why making a subwoofer box is not as simple as making a standard box?

A subwoofer box must be constructed to specific measurements, both inside and out.

You need to ensure proper room for the speaker itself, as well as air volume around the electronic components for the best sound quality, especially if you upgrade and install the other speakers in your car.

Speakers need to be reinforced heavily with glue and screws to prevent distortion and damage over time from the vibrations.

A standard box will likely not be made strong enough to withstand the intense vibrations that a subwoofer will create, nor will something standard have any airtight features to keep the background (air) volume muffled better inside the box.

Assembled subwoofer

What is the purpose of a subwoofer box?

Improving bass response.

A subwoofer enclosure that is made correctly can increase the sound quality of your subwoofer.

The bass response will be much higher and the distortion from vibrations will be eliminated.

 

Protect subwoofers from damage.

Having a properly sized box will prevent your subwoofer from suffering damage due to over-excursion. This is the term used when a speaker is pushed past the electrical limits of the technology.

The internal and external vibrations, if not contained correctly, can quickly destroy the speaker itself.

What to consider before making a subwoofer box according to specifications

1. Speaker size

Your speaker size will directly determine what size of subwoofer box you need to build.

The size needed to accommodate the blast will also determine how much space you need to allow for, and the distance you need between speakers.

Here’s a tip on how to build a subwoofer box for deep bass.

A larger enclosure will have more air volume inside which will not allow your bass to reverberate as much as it would in a smaller and more properly sized space. This would be good for music that does not have a lot of basses. 

If you create a box that is much too small for your speaker size, the acoustics will not be as good and your bass reverberation will sound a bit off, and not as good as soundwaves should.

This is a common cause of distortion and overall poor sound quality from my experience, and from what I have noticed in many badly built and designed DIY speaker systems.

A customized subwoofer

2. Shape

Most standard subwoofer boxes are rectangles, however, there is no limit to the shape you can create.

Wedge shapes are popular for trunk installation, but custom creations in a variety of unique shapes can work just as well too.

A small subwoofer

3. Volume

 If you plan on playing music loud enough to impress those around you, a subwoofer box needs to be made to the highest quality.

This is to not only ensure you get the best sound quality possible but so that the speaker does not self-destruct under the intense vibrations made from, your favorite musical instrument – the base.

4. Your amplifier

If you will be housing an amplifier with your subwoofer speaker, this needs to be taken into account for both added size as well as containment within the speaker box. 

Choosing the types of subwoofer enclosures

1. Sealed enclosure

These are the most common type of enclosure and are best for any general or all-around purpose.

They are great for providing an accurate bass return regardless of the size of the speaker and the volume of the music you are playing [1].

Subwoofer box with sealed enclosure

2. Vented or ported enclosure

If you’re looking for an enclosure that is made to be used with extremely loud and high-base music, portable boxes are the solution to your question. 

Building vented subwoofer boxes to specifications is highly recommended for efficiency while providing a booming return from your low bass frequencies and tones.

A vented enclosure

3. Bandpass

This is a unique combination of the sealed and vented enclosure.

Bandpass includes a plexiglass window and is great for displaying vehicles at shows or exhibitions.

When you’re ready to stand out from the crowd and turn heads with your music setup, this is the one to go with.

Measuring your subwoofer

1. Speaker diameter.

This is by far the easiest measurement to get. This measurement is easily found by measuring the subwoofer you will install across the mainframe.

Do not include the mounting frame or security lugs in the hole cut from your box, as the speaker frame should lay directly over the support. 

2. Cutout diameter.

When getting the speaker diameter, the cutout diameter would be the measurement of the speaker with the mounting frame and holes.

This measurement will ensure the cone and surround can clear the mounting plane of the enclosure box.

3. Mounting height.

Always get an accurate measurement of the subwoofer’s projections on the top and bottom.

This will ensure the speaker does not project outside of the box you plan to build or install the subwoofer components within.

4. Mounting depth.

Similar to the mounting height, this is the measurement of the subwoofer’s front and back components and projections in comparison to the mounting frame.

How much space is needed for different subwoofer speaker sizes?

To properly make a subwoofer box at home, you need to know the right amount of space and specs needed for building the enclosure.

The cubic feet measurements shown above are the generally recommended sizes.

You can make the space larger or smaller to suit your unique needs and the space you have available for the enclosure itself.

However, design-wise and working with speakers keep in mind that adjusting the size larger or smaller can also have a direct impact on the sound quality and longevity of the subwoofer you plan to build.

A larger enclosure will provide more volume of air around the subwoofer. This can create a flatter-sounding bass, and this is great for music that does not use a lot of bass in the first place.

Smaller enclosures will limit the sound quality as they have a lower acoustic resonance. They will also vibrate much more overall which can lead to your subwoofer wearing out much more quickly.

Size:Space needed:
6 inches0.300 cubic feet
8 inches0.375 cubic feet
10 inches0.625 cubic feet
12 inches1.25 cubic feet
10 inches2.83 cubic feet

How to calculate a subwoofer box size to get dimensions?

Calculating the area.

o calculate the area of a rectangle or square, multiply the length by the width. The answer will give you the area inside your used measurement, be that inches or millimeters.

To calculate the area of a triangle or wedge, multiply the base depth by the height to the tallest point and divide by two.

Calculating the volume.

Multiply the height by the width and the length of your subwoofer box.

The resulting answer is your total interior volume in cubic feet, inches, or millimeters depending on what measurement you used.

Materials for your subwoofer boxes

Plywood

While plywood is probably the most readily available and cost-effective material for most people, it isn’t as easy to work with as MDF, while ply is also more subject to more movement with weather changes.

If you live in an area with crazy hot summers and beer cold winters, expect to be replacing or at the very least resealing your subwoofer box annually if you don’t use plywood correctly.

  • Use wide structural grade plywood (Standard plywood glue shreds over time).
  • Use a biscuit joiner to strengthen joins and use lots of glue on the joins.
  • Use a sealer or paint to protect the plywood from moving and breaking any air-tight seal.

A stained wooden subwoofer

MDF

This is without a doubt one of the most popular materials used into build subwoofer enclosures. the man-made board is highly durable as long as it doesn’t come into contact with any water.

This material is easy to cut, and sand and can be found in a variety of thicknesses.

The medium-density fiberboard made from recycled wood chips is dense and can help increase the overall sound quality output from your subwoofers, better than plywood can, as plywood is usually less dense.

Hardwood

This is the best-looking option on the list, and it can be stained or left natural.

The biggest issue is finding wood that does not have any knots or grain imperfections as these can crack or warp over time.

Sketching your subwoofer design

For sealed enclosures, the design size is critical for matching the drivers and enclosure space, plus you need to ensure that the amplifier can deliver without causing any damage to the driver parts [2].

In order to sketch your subwoofer box design, you must ensure you have the proper measurements beforehand.

Determine the minimum depth, height, and available space you have in your vehicle before you get started. 

Using the dimensions you worked out above, start sketching out the shape you want to go with.

Rectangles are the most common choice, either horizontal or vertical depending on where you will be installing them, but wedge or triangle shapes are just as easy to construct and can work better in your vehicle.

In this case, you have to know each part of the speaker.

Sketching a speaker design

What you’ll need before building a subwoofer box?

  • Circular Saw or table saw
  • Drill with wood boring and screwdriver bits
  • 2 and 3-inch screws
  • Wood glue and silicone caulking
  • MDF or other material of choice
  • The subwoofer hardware and related components
  • Cabling and connection hardware

How to build a subwoofer box to specifications?

Step 1. Measure and sketch.

After you have determined your measurements and sketched the shape you want to go with, use a table saw or circular saw to cut out all of the panels from the MDF or other material you have decided to use.

Ensure your cuts are as straight and square as possible for the best end result.

Cut hole inside a subwoofer

Step 2. Find the center and cut the speaker hole.

Use an X from each diagonal corner on the front piece to find the center. From the center, make a circle that fits the size of your speaker, leaving an overhang to secure the mounting frame.

Use a compass or the template that came with your speaker for this part.

Or attach a string to a nail in the center, and around a pencil at the right length, then use the string or old wire as a custom compass to work as a marker.

Before cutting out the hole using a cordless jigsaw tool.

Sanding a subwoofer

Step 3. Assemble the enclosure.

Use wood glue and 2 or 3-inch screws to fit together with your rectangle box, or triangle box if that is the shape you went with.

Ensure the glue is given plenty of time to dry, and that all pieces are secured together as straight and accurately as possible.

You want your subwoofer box to be as secure as possible to ensure the absolute best sound quality.

Step 4. Cut the terminal and wire access.

Use the template that came with your subwoofer to make the hole on the back panel. This will be for your terminal and wiring.

Always check for the template before cutting any holes as your terminal should be either round or square depending on the speaker model.

Step 5. Caulking and Carpeting

Use the template that came with your subwoofer to make the hole on the back panel. This will be for your terminal and wiring.

Always check for the template before cutting any holes as your terminal may be either round or square depending on the speaker model.

Caulking a subwoofer

Speaker Carpet  

  1. You will need to remove your speaker and terminal posts first. Route the wires from the subwoofer to the terminal before securing the carpet.
  2. First cut to size, and apply glue to the wooden. Wrap the carpet around the speaker. Be generous with the glue and use staples to hold the fabric down until the glue dries fully.
  3. Use a box cutter or razor blade to remove the carpeting from the speaker and terminal holes. Allow excess so that you can wrap the carpet all the way inside with room to staple the edges on the other sides that can’t be seen. 
  4. Now reinstall the terminal box and speaker over top of the carpet.

Step 6. Finishing the installation.

Decide how you want to finish the speaker box, you could paint it, stain it, polyurethane it, or line it with speaker carpet.

Spacing inside a speaker

Paint or polyurethane?

  1. Fill any holes using the right color filler, or builders bog if you’re going to use paint.
  2. Sand the box using an orbital sander or a finishing sander.
  3. Apply an undercoat and 2 or 3 coats of paint, or 3 coats of polyurethane. Allowing for full dry time in between.
  4. Enjoy your New Subwoofer Enclosure
  5. Place the enclosure in the trunk of your vehicle or another place you had in mind and enjoy the great bass sound quality your DIY boom box produces.

Tips for building a subwoofer box

  • When building a subwoofer box, regardless of the size, do not use nails. Always use screws. Nails will vibrate out over time and can cause your enclosure to fail and squeak like a mouse.
  • The stability of the box is extremely important. Don’t be afraid to add internal braces between the walls that separate your speakers or your speaker and driver.
  • Ratchet clamps are an excellent item to use when securing panels together with glue. If your glue has a long curing time, clamp the box together tightly and let the adhesive set overnight until the glue fully cures for a tight grip.
  • If you are working on a theater inside your RV or campervan also consider an RV TV mount with an extendable arm.

A painted assemkbled subwoofer

Time to DIY your subwoofer box

Building a custom subwoofer box might seem complicated at first if you are new to doing some DIY, but once you get started you will see how quickly and easily the pieces just fall into place.

The most difficult part will be determining the size and shape you need to work with your subwoofer speakers as well as the space available in your vehicle.

Aside from that, the actual construction and installation are quick and easy and can be done over the weekend!

More information:

  1. How to build a subwoofer box, published in https://www.kicker.com/how-to-build-a-subwoofer-box
  2. Building a DIY sealed subwoofer, https://www.audioholics.com/diy-audio/diy-sealed-subwooferfor

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Hi, my name is Johann Holsinger, here at mountyourbox.com I share all of the tips and tricks I have professionally learned to help you set up your ultimate home entertainment system.