How to Build a Ported Subwoofer Box
Need a sub box but don’t want to spend loads? In this article, we explain how to build a ported subwoofer box without needing all the expensive professional tools.
Of course, you will need some tools, such as a drill, a jigsaw, and a few other bits, but this is the least expensive way for building custom subwoofer boxes from scratch.
Getting your sub box right is incredibly important, because it can have a dramatic effect on your subwoofer output. It has to be the right size, and even the port can have different effects if you put it in different places.
In this article, we guide you through the full process for how to build a ported subwoofer box. Before we get going, however, if you want to build a sealed enclosure, you can follow the steps with slight differentiation.
It’s pretty much the same way to assemble it, but of course you will need less pieces of MDF and it will actually be easier to build.
The cost for your parts, should be around $30 and it should take you no longer than an hour to put it all together, once you have it all ready at home.
So, with all that said, let’s look into how to build your very own custom ported subwoofer box.
Tools You’ll Need
- Electric Drill
- 2″ Wood Screws
- Wood Glue
- Silicon Caulk
- 2 Binding Posts
- Sound Deadening Mat
- Speaker Box Carpet (optional)
- Adhesive (optional)
How to Build a Ported Subwoofer Box
Determine The Size Enclosure You Need/Want
When you’re looking for a subwoofer, take note of the manufacturer’s recommended enclosure size. The box volume (cubic ft) tells you how big your enclosure needs to be for maximum performance from the sub.
Every subwoofer manufacturer will offer the minimum and maximum size subwoofer box, and you shouldn’t build a sub box outside of these guidelines.
If you’re not sure of the exact size of the custom subwoofer box you intend to build, you should go to this subwoofer box calculator, and enter your details into the online calculator. Add as much detail as you can into the ‘Box’ ‘Subwoofer’ and ‘Port’ tabs and it will calculate the perfect size your custom subwoofer box should be.
It’s a great tool and it will even design a truly customised ported subwoofer box, in which you can offset the subwoofer mounting hole and place the port at whichever side you choose.
There’s an option for double thickness on the front panel. I would recommend this as it will make your box stronger to hold your subwoofer in place.
Once you put all your specifications into the calculator, it will design it for you with the size cutouts you need. And best of all, it will show you your design in 3D.
Take Your Box Measurements To Hardware Store To Get Cuts
When you’re satisfied with the plan and the subwoofer box measurements, you want to take your cutout measurements and go to the hardware store to get your MDF and other tools and bits.
The sub box calculator will tell you the optimum thickness the MDF should be, and it’ll be around ¾”. Anywhere around this thickness will be perfect, but I wouldn’t go as low as ½” as that would be too thin.
If you go to Lowes, or B&Q in the U.K., they will likely cut your sides to size for you. If not, you’ll have to cut it to size yourself. Either way, always buy a bit extra as you’ll need some spare timber to work on at the very least.
Prepare Panel Edges and Draw Outline of Panel and Port Placements
Whether the hardware store cuts your panels, or you did it yourself, you need to make sure the edges are nice and straight. Check them all and maybe sand any down that have a rough edge sticking out.
Now it’s time to draw the layout of the front, back and sides of the outer walls of your sub box and the ported wall. Draw the outline on the bottom panel, just so we know where to drill the pre-holes.
Drill Pre Holes Through Top and Bottom Panels
First thing to make sure, whenever you’re drilling, always have some scrap MDF underneacth so you drill into that instead of your workbench.
Once you have drawn the outline of all panels on the inside of your bottom panel, get the top and line it up exactly with the bottom and drill through both with the pre-hole drill bit. Doing it this way is both faster and you get the screw holes in the exact same location on the top and bottom.
Then on the outside of the top and bottom panels you want to drill a countersink, so your screws won’t stick out when you drill them in. Make sure you drill all holes into the top and bottom, and when you’re done, it’s time to sand them down so there’s no sharp bits sticking out.
Screw and Glue Ported Panels Together
Now it’s time to drill the holes in the sides, where the screws are going to be screwed in. Now, because we’re doing this with MDF, it’s important to drill the pilot holes into the edge as big a diameter as possible.
This is because MDF is pretty weak when drilling into the edges, and if your screws are quite a bit bigger than the pilot holes you drill, it could crack the MDF. The screw only needs to be slightly bigger than the holes – as long as the screws grip a bit and the glue, the fit will be secure.
First you should do the two parts of your ported walls. You should already have your pre holes drilled in place. Now put the four screws in on the outside of your panel ready to be drilled through, then run some wood glue down the edge of the other piece.
When you have it all lined up, drill the four screws in tightly. It’s best to drill the 2 outside screws in first so you don’t go out of line as you drill them in.
Once the ported walls are secured, you should fill the countersunk screw holes with a filler. You should also make sure the L-shaped interior edges of your sub box are rounded as much as possible.
The rounder the ported wall is the smoother the soundwaves will be able to travel. When this is done you can leave the ported wall until you have the outside edges and bottom secured together.
Now Fix The Rest of Your Panels as You Build Your Custom Subwoofer Box
Now you’ve got your ported panels ready, it’s time to build the side panels together and then fix them to the bottom panel.
To do this, you need to line up the bottom piece with each wall (one at a time), where it will sit. Then drill through the pre-holes and down into the left, right, front and back wall edges, where the screws will go.
Now you can start fixing the sides together. First, get the left and back – run some glue all the way down the joint and then line them up perfectly, put the screws in and then drill the screws in tightly. Any excess glue that protrudes from the joint, just wipe it down with your finger and this will help seal the joints further.
As you fix all panels together, run some silicon caulk down each edge to secure each joint. Do this with every panel joint.
Now do the same with the right and back so you now have 3 pieces glued and screwed tightly together.
Now it’s time to screw the bottom on. Again, make sure it’s turned around the right way so you can put the bottom piece on top of the 3 walls (this makes it easier to drill the screws in). Then put all the screws in the bottom so they’re ready for when you drill them into the sides.
Then run some glue down the three edges that you’re fixing together, sit the bottom on top of the 3 sides and screw all screws into each pre-hole and make sure they’re all tight. Again, run your finger down the joint to wipe away any excess glue.
Now you can do the same with the L-shaped ported piece, always making sure you wipe away the excess glue.
Now, do the same with the top. This should be screwed and glued onto the side and ported edge so you now have a closed subwoofer box with the ported gap on the front to the side.
Cut Out Wire Terminal Connection Points
Many people go with a terminal cup to wire a subwoofer up, but I don’t recommend these. They’re made of thin plastic and air will get out of your sub box if you use them, so I don’t recommend using them.
Instead you should use 2 Binding Posts for your connectors. For this you should drill 2 holes into the back of your subwoofer box.
The 2 holes should be slightly smaller than the diameter of your binding posts, and then you need to thread the binding posts into your back panel and secure them in tightly.
Drill the holes as close as possible to where your speaker wire terminals are in your subwoofer. And if the wires are to sit on the base of your enclosure, it’s a good idea to stick some sound deadening material under them so you dampen the rattle.
Cut The Subwoofer Mounting Hole on The Front Panel
You should have everything together, except the top and your mounting hole where the subwoofer will sit in your custom box. Now it’s time to cut the mounting hole in your custom subwoofer box.
You could do this before you build all your subwoofer box together, but unless you have a professional set up, you will need a clamp and some space under the front panel to make it possible to cut the hole out.
The first thing you need is the actual center point of your front. To do this, get a straight edge so you can draw diagonal lines from all four corners to the opposite corners. The meeting point of these will be your center point.
Drill a small hole in the center point, so you can drill your compass template into this to get your perfect circle.
Now you need a spare piece of thin cardboard that’s longer than 50% of your cutout diameter. My Kicker 43CVR124 CompVR has an 11” cutout diameter, so I will use this as an example.
In your spare piece of cardboard, pierce 2 small holes that are just over half the length of your cutout diameter. Mine is 11”, so my 2 holes are 5.55” apart.
Now drill a screw through one hole into the center point hole that you just drilled in your sub box. And with a pencil piercing through the other hole, move your cardboard around in full circles, so you draw an 11.1” circle on the front of your sub box.
*You can do this with a compass if you have one large enough.
Now, measure your circle to make sure it’s exactly the size of your cutout diameter. If it isn’t you must have drilled the 2 holes in your cardboard the wrong distance.
Next, drill a large enough hole close to the edge of your circle (on the inside), so you can get your jigsaw inside.
Now with your jigsaw, you need to cut right around the inside of the circle you have drawn. It’s important not to cut exactly on the line as this might end up being too big, and you can always shave more off if it’s too small.
Once you’ve cut the hole, sand it down so you don’t have any rough edges. Then clean out the insides with a vacuum cleaner so there are no loose wood shavings.
Time To Test Your Math and Carpentry Skills
Now it’s time to test your math and carpentry skills and sit your subwoofer in to make sure you have the right size mounting hole for your subwoofer. And that’s it you’re now a master at building a subwoofer boxes.
Basically, that’s how to build a ported subwoofer box. You can finish the exterior if you like. The countersunk screw holes don’t have to be filled on the exterior, but if you paint it, it would be a good idea to.
Or if you want to do the best job possible, you could cover the exterior with some vibration reduction carpet. This will ensure you get the best sound from your newly built sub box.
Installing Your Newly Built Subwoofer Box
You should really know where you intend to install your subwoofer box, and this obviously depends on the type of vehicle you have and the space you have available.
Wherever you intend to install your sub box, it’s best to put some sound deadening material under the bottom so it’s sitting on some.
Also, if the back or any side of your subwoofer box is tight against a wall of your vehicle, put some sound deadening material between your box and car interior. This will ensure you cut out the vibrations, and increase the clarity of your bass from your new installation.
Having read through this step-by-step guide you now know how to build a ported subwoofer box. Of course, the steps to building a sealed subwoofer box are the same, but you’ll need less timber and it will be easier to do.
As long as you go to the Sub Box Calculator and put the correct specifications in, you can’t go wrong for your panel cutouts.
It can be a little awkward when you’re first putting cutouts together, but as long as you make sure the joints are exactly matched, your new custom subwoofer box will come out perfect.
And the best thing is, now that you know how to build a subwoofer box, you can build them for your friends and make some extra cash!
Have you built your own custom sub box? If so, how did it go? Please share your story in the comments section below to help anyone intending to do it in the future.
I am a passionate and skilled car audio enthusiast with 15 years of experience in the industry. My journey started when I replaced my first set of factory car speakers, sparking a deep love for high-quality sound. Since then, I have worked as a representative for renowned brands like Kenwood and Alpine.
With a background in both retail and distribution, I have developed a comprehensive understanding of the car audio market. Currently a certified (MECP) installer in the Mobile Electronics industry, my expertise lies in delivering top-notch audio installations. My knowledge, coupled with my genuine passion, makes me the go-to professional for all car audio needs.