What are the different categories of subwoofers?

The classification of subwoofers can be done from multiple dimensions, and the following are some of the main classification methods:

1、 Classified by whether there is a built-in amplifier or not
     Active subwoofer: Integrated with a power amplifier, it can directly connect to an audio signal source and amplify sound without the need for an external amplifier. This subwoofer is very popular in home theaters and car audio systems because they are easy to use and can provide sufficient power.
Passive subwoofer: It does not have a built-in power amplifier and requires an external amplifier to function. This type of subwoofer is more common in the field of customized installation, as they can achieve more flexible embedding and better heat dissipation control through external amplifier design.

2、 Classified by box design
     Sealed subwoofer: The entire enclosure is sealed without any ventilation holes. This subwoofer uses a fixed air volume inside the speaker to generate resonance. It has a small volume and can withstand high power, making it suitable for playing at high sound pressure and helpful for extending low frequencies.
Reflective subwoofer (bass reflex subwoofer): The cabinet is equipped with a sound outlet (inverting hole), and the sound waves radiated backwards from the speaker are inverted through a duct and radiated forwards from the sound outlet, where they are superimposed in phase with the sound waves radiated forwards from the speaker. This subwoofer can provide wider bandwidth and higher sensitivity than enclosed speakers, making it the most widely used type currently.

3、 Classify by sound direction
     According to the different directions of sound, subwoofers can also be divided into various types such as front facing sound, rear facing sound, ground facing sound, upward facing sound, and left and right facing sound. This classification method mainly affects the placement and listening effect of the subwoofer.

4、 Other classification methods
     According to the interfaces and functions of subwoofers, they can also be divided into subwoofers with USB, FM, TF, TWS, Bluetooth and other interfaces and functions. These interfaces and features make it easier for the subwoofer to connect and use with other devices.

      From a technical perspective, subwoofers can be further subdivided into various types such as low-frequency reflex design, strip design, and transmission line design. These design methods each have their own characteristics and are suitable for different application scenarios and requirements.
In summary, there are various ways to classify subwoofers, and consumers can choose the appropriate subwoofer type based on their needs and budget when making a choice.