David ordered black MDF from OPMAATZAGEN.nl to make his own speaker box. He extensively documented the entire project! Follow along with David's approach and get inspired to start your own sound box!

Self-Built Speaker Box Report

In the past, I once built a speaker box from MDF from the local hardware store. To start, the dimensional accuracy was not great, they do their best, but it remains a struggle. After a lot of sanding, fitting, and measuring, it finally came together, but the MDF was rubbish. Like softboard. Primer made all the fibers stand upright, so sanding, repriming, etc. Even after 10 layers (with several days in between to let the primer dry), it was still not good. To top it off, the wood was too soft to properly screw in a speaker. Terrible. The work took a lot of time and effort, and the result was not worth it. At such a moment, you realize you're not a woodworm.

Recently, I wanted to build a sound box again, but not with such rubbish MDF. By now, I had heard from a professional that there are different qualities of MDF, and that the hardware store MDF is not top quality, but rubbish.

How I made this project

Google is your friend, so I ended up at OPMAATZAGEN.nl. After a pleasant email exchange to make sure that custom-made is really custom-made and that the MDF is top quality rather than rubbish, I ordered.

Because I always find the ends of MDF difficult to get flat, and OPMAATZAGEN.nl can also make miter cuts, I decided to go for full miter (exterior). Although with through and through black MDF this wouldn't be necessary, but I liked the material so despite the extra cost, I chose it.

Actually, a huge acid test, with the chance that I could throw my money away. The box is 53.0 × 32.0 × 28.0 cm, so ordered front, back, sides, and top/bottom in that size, without subtracting the material thickness. After all, it is miter cut. Only the sizes of the internal partitions/reinforcements need to be calculated.

It will be an active box, so with the electronics built-in, and for that, I needed some extra shelves. In the end, I ordered the following for my MDF speaker box:

The order was delivered and I could get started!

The wood arrived overly packaged within 3 days at my home, and I was immediately completely thrilled! This looked absolutely perfect. Super accurately cut, beautiful heavy MDF, and not a single flaw to be seen. I didn't prepare anything for the wood (no sanding, etc.) and started gluing it together the same evening.

Gluing the Miters

Well-mitered stuff is easy to glue: place the parts to be glued with the sharp edges tightly against each other on a flat surface (align well) and stick painter's tape over the parts. This creates a 'hinge'. Turn the parts together, thinly coat the angled (miter) parts with glue, spread the glue, and carefully fold the parts together. Press out the excess glue from the joint.

I used one of the non-miter cut 'bulkheads' to get the corner exactly at 90 degrees, although it actually went well by itself. I used quick-drying wood glue (Pattex Express D2 from Henkel). Great stuff. Fast-drying Bison wood glue D2 will work just as well.

After gluing a back and a side together in this way, I glued some intermediate partitions. If I had glued both sides, I wouldn't have been able to get in between them with a partition anymore. Some thinking about the order is therefore necessary!

Gluing the Partitions

Gluing the partitions went fine, everything turned out alarmingly accurate. Not only accurate to the millimeter, but even better than that!

After all the interior parts were glued, I glued the other side and finally the front. I had previously cut the holes for the speakers in the front, with my jigsaw. This went very nicely, although it was considerably slower than with the hardware store MDF (it's really hard stuff).

Only the bottom and the lid remained to be glued, and at that point I got nervous. All the dimensional deviations would end up in the bottom and lid. Oops, did I handle it smartly?

After some fitting, I was reassured. I had apparently glued the parts accurately enough, and the sawing work is precise because the bottom and lid fit without gaps!

So, spread glue on the angled surfaces, and put everything together. Again with painter's tape to get and keep everything in place. Where there was no painter's tape, I wiped off the excess glue with a damp cloth each time.

Nicely cut to size, and now painting!

After all this gluing, it became clear again what had gradually become apparent: incredibly nicely cut to size, that MDF!

After a day of drying (glue), I decided to give the MDF a layer of primer. I'm a bit done with water-based paint, so I bought primer and enamel paint based on turpentine.

After degreasing with Thinner, I lightly sanded the outside with sandpaper 600. It wasn't even sanding, because the MDF is already quite smooth. I slightly chamfered the sharp edges that had formed after gluing the miter-cut parts together. De-dusted (cloth with Thinner) and then rolled everything (except the bottom) in primer. No MDF primer, but just wood primer, and then diluted by about 5% (Turpentine). The MDF hardly absorbed anything, and the result is great. With sanding and priming together, I wasn't even busy for an hour. Wear a mask while sanding because MDF dust is carcinogenic.

After rolling with a foam roller, the primer doesn't seem smooth, just leave it like that, it will smooth out. Especially do not roll again later, it will only make it less smooth. I let the primer harden for 5 days because I don't want a base layer to still be a bit soft. After this hardening, I sanded again with sandpaper 600 (again little effort) to get everything nice and smooth. Since I didn't strip anything bare, I started rolling the first layer of enamel paint. I also did this with a foam roller. If you don't press too hard, a foam roller won't create bubbles, you won't push air into the paint. But unfortunately, this paint hadn't read the book. Next time, I'll use a Mohair roller. A bit more expensive, but even smoother!

After this one coat of semi-gloss black, I find the finish sufficient for now. Everything is covered. The lacquer layer is not 100% perfect yet, but I have to finish assembling the speakers, get their tuning (filtering etc) in order, and I'm still busy with that. Perhaps, in the long run, I'll sand it down again and roll it once more with a better roller.