In this article we will consider the 3 main types of subwoofer enclosure and establish the pros and cons for each type. It is important to firstly match the subwoofer mild steel enclosures that you have to an appropriate type of enclosure, and also it is important that you know what you want to achieve when choosing the subwoofer and the enclosure type. If this is not considered then you could easily end up with something that either just thumps away loosely in the background drowning out all the other frequencies or does not produce the levels of bass that you want.
The three types of enclosure that we will be looking at are sealed enclosures, ported enclosures and bandpass enclosures. Each of these enclosure types will produce different effects on the sound that is produced. They will also all produce different results depending on the specifications of the subwoofer you choose. This article covers the different characteristics of these 3 main types of enclosure.
Firstly we will look at the easiest to design and to make, the sealed enclosure. This type of enclosure has a subwoofer on one wall facing out. The inside of the enclosure is sealed so the air inside the enclosure is kept separate from the air outside the enclosure. The main characteristic of this type of enclosure is a smooth frequency response meaning that the bass frequencies will remain at a similar level throughout the frequency range. This type of enclosure will also give the cleanest tightest sound reproduction. The problem with this type of enclosure is that to produce very low bass very loudly you would have to use a large enclosure and subwoofer that was capable of moving lots of air. The volume of the enclosure should be matched to the properties of the subwoofer for best results.
The second type of enclosure that we need to consider is the ported enclosure. This is very similar to the sealed enclosure except that it has a port which allows air to be pushed out of the enclosure through this port. The effect that the port has is to increase the bass response at a certain frequency. This effect will cause more bass to be produced across a narrow band of frequencies. Therefore it is possible to get greater volume from your subwoofer than you would typically get from a sealed enclosure. The trade off from this is that you will also lose some agility in the sound. The bass will appear to be less precise than the equivalent sealed enclosure.
The third type of enclosure is the bandpass enclosure. This type of enclosure will contain at least 2 chambers. The subwoofer will be mounted between them on the inside of the enclosure. One of the chambers will be ported allowing the waveforms to travel into the external environment. This type of enclosure will usually have multiple ports in order to maximise the frequencies that will be heard. In order to achieve this, the ports are usually different sizes as this influences the frequencies that will tend to travel out through the ports. A bandpass enclosure will give you lots of bass over certain frequencies but this will again come at the cost of precision.