Making a sub-woofer box is one of the more difficult things to do in a DIY sense. Boxes need to be made that are the same size as your receiver and center speaker, have a hole cut for the sub-woofer, and must be of enough material not to vibrate. This blog post will go through all the steps necessary to make this project and will show off an example of what you can do with it!
How To Make Home Theater Sub-Woofer Box
It’s often difficult when it comes to building boxes around audio components, but with some patience and diligence, you can do anything. I’ve found a few sites on the Internet that address the process of making a box to hold an audio component, but most only go through one step at a time. This post attempts to cover all the steps required for this project.
You won’t need to buy anything for this tutorial other than your trusty tape measure and laser cutter. I used my Craftsman Laser Cutter we built in A Guide To Setting Up A Laser Cutter For Home Makeover,. My cheap $20 Harbor Freight laser cutter can handle fabric, paper, cardboard, but not wood or plastics. I bought this pack of staples to go through the boxes with each step.
Measure and mark the holes for the speaker. This is where most people will have difficulties. It’s hard to imagine when you are starting a project that your cut out will turn out perfectly, especially because you aren’t going to do it over and over again. When I started this project I was going for a square box with straight lines all around it. Well, I had no idea how big my speaker was and I made the hole too big for my center speaker which caused it to be too loose in the hole. I had to get a new speaker for my setup, but I had to fix this problem first by cutting out the hole one more time.
I ran into the same problem again. I didn’t look at my drawing and measure how deep I needed the speaker slot to be. Instead I just decided it was close enough. Well, it wasn’t close enough for a pair of headphones! They rattled around in there after I put them in! So, back to step one. This time I didn’t make a square hole like before so that it would fit my speaker perfectly in it with no rattling or jumping around and hitting the inside of the box when turning on or adjusting volume (very annoying).
After making all sorts of mistakes, I finally got the hole right (1 1/8th inches wide) and put the speaker in it perfectly! All that is left is to cut out the rest of the box and make sure that it fits your center channel. It took me about 10 cuts before I could get it looking like a box. I could have saved myself a lot of time by measuring my speaker first to get the size and depth of the hole perfect on the first try.
Clean up your work area which is now covered in sawdust. Lay down the box template and trace it onto your masonite board. You can also use a hinged door from a cabinet or something similar, but this material should be about as thick as you can get that you can cut yourself. The speaker will vibrate this board and you don’t want it to crack. I’ve seen some people use plexiglass for this because it is strong, but it’s not very practical because if the speaker vibrates enough you end up with scratches on the surface of the box or cracks along the edges of it especially if you are using a cheaper laser cutter like me.
Once you have a box cut out, measure the depth from the top of the speaker hole to the bottom of the box. The depth is the distance in which you will fold back on your masonite board so that it fits into your laser cutter. If you are using a hinged door, be sure that when you fold it back there are not any sharp edges or if there is material caught between them then cut off some of it so that they fit together perfectly. If you would like to omit this step then skip down to Step 6 and just make a long straight cut through your board without folding it back.
You can optionally omit the folding on your masonite board if you want to save yourself some time. When using a laser cutter, it’s better to cut through masonite and make a straight cut so that there are no worries about getting the material too course or catching litter between them. I didn’t add the fold back step so that I could make it fit exactly in my laser cutter but if you are worried about having to change another setting in your laser cutter, then do this step. Measure the depth of your speaker box (from the top of the hole all the way down) and make a long straight line starting at one end of your board and ending at the other side.
Using your tape measure, measure the length of your masonite board from one end to the other. If you are not using a hinges or it’s not going to need one later, then your measurement is all that it will need and you can go ahead and cut out your box. If it is going to need hinges or if you want to add more depth in which case the board will be folded in half lengthwise, then add a bit more material to the board so that it is wider than your hole when folded in half (so that it fits snugly under the laser cutter). Measure this amount before cutting so that you know how long to leave a hinge on it.
Glue the hinge at the desired location of your box and make sure that you have enough pressure on it so that it holds the material in place without ripping the hinges off. Do not glue down your top piece as much as the bottom piece because you will be stepping on this while out doing your measurements. Glue down one side of your board to secure the hinge, then glue down the other side to secure it all the way around. If you are using a hinged door, use a clamp like I did or just brace it against something else to prevent it from moving around while folding back on itself.
With your box now folded, you can measure the depth of your speaker hole with a tape measure and then cut off the excess. Be careful when cutting because you are working with two pieces that are glued together so make sure you don’t cut off anything else. Now that this is done, you are almost finished! We just have to add another piece of masonite to support the speakers soldered leads. If you have a dremel tool, use it to cut notches into the bottom of your box for the wires to go through without them getting in the way during use.
Place your speaker with the attached cable to the cutout in your box and mark where it needs to be cut on your masonite board. I used a flat head screwdriver to scratch away some of the excess material so that my box would fit flush against my speaker. Now use a file or sandpaper (depending on how smooth you want it) to smooth out this area of your masonite board. Be sure not to leave any rough edges or sharp spots either.
The only thing left to do is to attach the speakers soldered leads either to the back of your box or to one of your cabinet halves. I soldered them onto the back of my box because it was easier for me. Just be sure that you don’t overload your amplifier and blow it up! If you are using a smaller speaker like me, you should probably solder them onto an inch wide piece of wood so that they won’t get too hot during use.
Now that you have your speaker box (if you made it this far) all that is left is to put it somewhere near where you are going to be using it and then hook up your amplifier. I will show you how I put mine on the back of my TV cabinet since this is what is easiest for me to do. If you plan on putting your box outside, then just make sure to use a weatherproof box or hang it aboveground so that rain can’t get inside and ruin everything! Press the power button on your amplifier and plug in your speakers. If everything worked like it should then you will now be able to hear the sound much better. Mine was very quiet at first so I had to turn my amplifier up quite a bit, which is why it looks like I blew out the picture on my TV.
I used this speaker box for a while before finally deciding that is was too small for my liking and the speakers were just too close together. The material that I used to make the box wasn’t exactly very strong either so I knew from all of these problems that if I was going to do another project, then I would definitely be using something stronger than masonite. Luckily, there are many types of materials that you can use including plywood. You could also use aluminum or fiberglass if you have some laying around.
When using plywood, you can make it in a number of different sizes so that you can fit your speakers to the size that they need. I also wanted to use something else besides masonite as well because I always thought that it looked flat and plastic-y even though I know that it’s supposed to be spongy and soft. For this project, I decided to use 3/8 inch plexiglass which is slightly transparent like glass or plastic but you are not going to really see through it because of the refraction off of the edges. You could also use acrylic which is much stronger than plexiglass but it would be much louder so I went with the less expensive material in the hopes that I wouldn’t blow my amplifier.
Using a jigsaw, cut out two pieces of plexi (one for each side) and glue them to each of your speaker box sides using your regular glue. Be sure not to place them too close to the ends of the box because you don’t want them to crack when you roll up the speaker box. I would also recommend using clamps to hold them together for a longer period of time since it is going to take a bit of time to dry. Also, when you do this, put the glue on the inside of your speaker box and not the outside because otherwise, you will be faced with a messy sticky mess.
Now that the glue has dried, place your speakers in the newly formed speaker box and mark where you want it cut out on your plexiglass. You can use a tool like I did or just cut it out with a blade. Before cutting it out be sure to measure the depth of your speaker box and make sure it is small enough to fit inside of your plexiglass. You could also use a jigsaw again to cut out the final piece of plexi that will cover your speakers, but I like using a saw blade because you can always have new stock of plexi if you so choose.
To finish this project, turn your amplifier back on and test it. Make sure that you can hear the speakers in the sound and that none of the wires are pinching off under tension.