Do You want Subwoofer Plans that will Crush Competing Subwoofers?

Decide on your subwoofer design budget

This is going to be a determining factor for the level of parts you will be able to start with. A subwoofer box design needs to have good parts in order for everything to work well together. Cheaper parts will most often mean sacrificed performance.

Decide on a configuration, sealed, ported, band pass, etc.

If you are taking the time to build a subwoofer do a little bit of homework to make sure its going to work well. There’s no point in building a nice box that sounds terrible because you didn’t bother to do some simple calculations based on the Thiele Small parameters and optimize the box type, volume, and bracing.

Many designers may disagree with me here but I feel the box type needs to be chosen first. In order to do this you need to establish the type of bass that you are after.

Ported Sub woofer enclosure

Do you play mostly movies and want bone crunching bass that has high impact? Maybe you don’t care about music that much, but if you do listen you like rap music and other bass heavy tracks? If this is you a ported box is likely to work really well.

Ported enclosures are also a bit cheaper to make, as the drivers don’t need to have quite the low bass extension as the port relieves the driver of some of the output.

Ported subwoofer boxes also don’t need quite as much power to reach the same SPL in-room.

It may look like I favor ported cabinets, I am not, ported boxes have their place but… a sealed subwoofer enclosure design is my preferred box type.

Sealed boxes are more costly to bring to the same level of output due to differences in the way that they work.

Sealed sub woofer box

If you listen primarily to music, want a high degree of accuracy, pitch definition, and don’t care about your teeth being rattled during movies, then a sealed box is likely better for you. However, if money is not a problem, a sealed box can also deliver all the positive attributes of a ported box, it will just demand a more expensive driver, more power, and possibly a very large box that is heavy and well braced.

Choose a driver that is best suited for the type of subwoofer box design that you want

This is where many start to bow out of the idea to build their own subwoofer. I assure you, it is not difficult. You can learn enough to start in a few hours of studying.

First, a very basic scaled down explanation of some key information you will need to know. These are known as Thiele/Small parameters (or T/S parameters). They are present in most data published for any reputable speaker manufacturer. If you cannot get access to the data, choose another speaker driver, as your results cannot be accurate without them.

Qts:

For a sealed driver this is usually best if over .37 Qts. Ported are usually below that so, .37 and lower for ported. This is not absolute and you can go over or below this. But typically, a sealed box will have a Qts of .37 to .60.

Qes

Same as above .37 Qes to .60 Qes for sealed boxes. Below .40 Qes, is usually best for ported boxes.

Vas

This is not the box volume you should put the driver in, but it is a good place to start. Using a speaker box calculator, enter all of the T/S parameters of the driver and then start to play around with the subwoofer plans 'box' volume.

The best volume is usually pretty close to the VAS. Optimal box volume uses the Qts, Qes, Qms, and VAS to determine optimal size.

Here are the calculators you will need to determine volume, and suitability of your drivers

Use to determine if driver is better for ported or sealed subwoofer plans.

Ported Box Calculator

Sealed Box Calculator

Next, build using your subwoofer plans using the ideal box volume, but also take into account for bracing

Use a calculator to measure the volume of each brace and subtract it from the volume of the inner cavity. You may need to adjust the volume up to stay at the ideal volume internally. Bracing is very important in a subwoofer. Don’t cut corners here. The good news is that if you design a brace that will work throughout the cabinet, you often can just use multiples of the same type of brace.

I would suggest that the outer walls have no more than 3” of space without a brace. This will inevitably increase the size of the outer cabinet from the number of braces, but it will increase the cabinet wall strength substantially, and keep transients very sharp and crisp.

A sloppy cabinet will not allow the speaker driver to operate with low distortion as the box will be adding its own distortion into the room. This is key, and one of the things separates good subwoofer plans from poorly designed plans. In fact the box is the most common fault in a good subwoofer. Most designers just don’t put enough consideration into the box itself.

It will be helpful to draw out a subwoofer diagram with the bracing and basic box structure that you want to use. Your subwoofer box plans need to incorporate all of the factors that affect performance. Include; power handling of the woofer, power of the amplifier, size of the box, T/S parameters, and an excellent bracing scheme. Subwoofer basics are critical to achieving a high level of success in your design.

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