There are several types of enclosures that you can use for DIY speakers, including sealed, ported, and passive radiator enclosures. Each type of enclosure has its own unique characteristics and will affect the performance of the speaker in different ways.
Sealed enclosures, also known as closed or acoustic suspension enclosures, are the most basic type of speaker enclosure. They are relatively simple to design and build, and are known for their smooth and extended low frequency response. However, sealed enclosures tend to have a relatively limited bass output compared to other types of enclosures.
Ported enclosures, also known as bass reflex enclosures, use a specially designed port (a hole or opening in the enclosure) to enhance the low frequency response of the speaker. Ported enclosures are typically larger and more complex to design and build than sealed enclosures, but they can produce more bass output and have a more powerful overall sound.
Passive radiator enclosures use a special type of speaker driver called a passive radiator in place of a port. Passive radiators are similar to conventional speakers, but they are not driven by an amplifier and instead rely on the movement of the air in the enclosure to produce sound. Passive radiator enclosures can offer a combination of the smooth low frequency response of a sealed enclosure with the increased bass output of a ported enclosure.