Design a sealed enclosure the easiest way possible

If you want to learn how to design a sealed subwoofer box, this article is for you. And when I said article I meant this video. Because I explain everything in that video, so go watch that. In this article I’m just going to add some minor commentary. In addition, here is also the place where you can download the excel spreadsheet. Finally, you will find the building plans for the active subwoofer mentioned in the video.

Excel spreadsheet

If you came here just to download the excel spreadsheet, I’m just going to place this at the beginning of the article.

Here is the Download link.

If it doesn’t download automatically, just right click and save as. This excel spreadsheet is very versatile. While it does not have all the bells and whistles, it get’s the job done super fast. Even today I still use it in the detriment of other sophisticated software. You just enter 3 parameters and you are done. While this article was meant to help you how to design a sealed subwoofer, this is especially fast for bass reflex boxes. When you are searching for a particular driver this is very handy, to quickly check the box requirement for each driver.

As a side note, I want to mention something which I missed in the video. If you want to model the response of a box with multiple drivers, you can do that. While I have not implemented an option to select the number of drivers, I simply do this trick. When you enter the speaker parameters, enter Fs and Qts like normal and for Vas multiply the Vas number by how many drivers you have. And that’s it. As a result, if you have 2 drivers just double the Vas value and keep Fs and Qts the same.

Parts list for active subwoofer project

Besides the 18 mm MDF we are using. Here are the 3 additional parts that you need. I’m going to list links for EU and US buyers. These are all affiliate paid links :

Seems like a short parts list, but this is a simple project, and all the complex stuff is integrated in the plate amplifier anyway.

How to design a sealed subwoofer – Enclosure overview

First of all, I want begin by letting you know that I used 18 mm MDF. Secondly, I want to swiftly post a picture with the overall dimensions. While this sub was meant to be a small one, the fact that the amp needs a separate air tight chamber, makes this box larger than it needs to be. As a result, even if I meant to make a small sub, this might not be that small after all. So check out the overall external dimensions.

how to design a sealed subwoofer box

So, the external dimensions are 300 x 292 x 446 mm (W x H x D). The front panel is small in my book, but the overall enclosure is pretty deep. In conclusion, please check this before you decide it’s a small box or not.

We settled on 23 liters of internal volume. However, if you measure the internal volume of the chamber the speaker goes into and subtract the volume displaced by the speaker, you will get around 18 liters. This is because we are going to fill it up with dampening material and the perceived volume will go up significantly. An estimate of 23 liters perceived volume is probably very accurate.

Panel dimensions

While we discussed how to design a sealed subwoofer in the YouTube video, here I’m going to give you the exact dimensions of the panels so you can build this project without any calculations.

Here is a list of the panels dimensions :

  • Front / Back : 300 x 292 mm
  • Top / Bottom : 410 x 300 mm
  • Sides : 410 x 256 mm
  • Internal panel : 256 x 264 mm

Next, I’m going to list the drawings of all the panels, so you know how to make the cutouts and where to place the internal panel:

how to design a sealed subwoofer enclosure Closed box sub subwoofer panels MDF panels

I think it’s straightforward now how the panels puzzle together. However, there is something I want to mention. The internal panels I made it 10 mm thick, to get the box size to a minimum. This might be an inconvenience to buy MDF of different thicknesses (10 and 18 mm). If you want, you could place an 18 mm panel there, in the same position and eat from the internal volume of the speaker chamber. It won’t make that much of a difference. In addition, you might want to consider predrilling some holes in this panel to route the wires from the amp to the speaker. Use some silicone in that spot so there is no air leakage. And that’s pretty much it. Have fun building!