Exploring Common DIY Terminology - Sealed Enclosure

Sealed Enclosure

A sealed enclosure, also known as an acoustic suspension enclosure, is a type of loudspeaker cabinet design used in speaker systems. It is one of the most straightforward and commonly used enclosure designs in the audio industry. The primary purpose of a sealed enclosure is to provide a controlled environment for the loudspeaker driver to operate optimally. The basic principle is quite simple: the loudspeaker driver (usually a woofer or midwoofer) is mounted on a baffle within a sealed box or cabinet. The cabinet is airtight, meaning there are no air leaks, and the driver is the only opening in the enclosure. When the driver moves, it compresses and rarefies the air within the box, effectively creating a sealed, air-spring system. Here's how it works:

• Air Spring Effect: When the loudspeaker driver moves inward (toward the cabinet), it compresses the air inside the sealed box. Conversely, when it moves outward, it rarefies the air. This air-spring effect acts as a restoring force, pushing the driver back to its resting position when no input signal is present.
• Lower Resonant Frequency: The sealed enclosure provides a stiff air-spring system, resulting in a relatively low resonant frequency for the driver. The resonant frequency is the frequency at which the driver naturally tends to vibrate or resonate without external input. In a sealed enclosure, this resonant frequency is typically lower than in other enclosure types like ported or bass reflex designs.
• Roll-Off Rate: A sealed enclosure has a natural roll-off in the low-frequency response. This means that the output level decreases relatively steeply below the resonant frequency of the driver. This roll-off is usually around 12 dB per octave.
• Tight and Controlled Bass: The sealed enclosure's roll-off rate contributes to tighter and more controlled bass response compared to some other enclosure types. It doesn't produce as much extended low-frequency output, but the bass it does produce is often considered more accurate and well-defined.
• Reduced Group Delay: Group delay refers to the time delay experienced by different frequency components of a signal passing through the loudspeaker system. Sealed enclosures typically exhibit lower group delay compared to other designs, resulting in better time coherence and improved transient response.

While sealed enclosures have several advantages, they do require more power to achieve the same volume levels as ported or bass reflex designs. Additionally, they may not be as efficient in producing very low frequencies due to their natural roll-off. However, their controlled and accurate bass response makes them popular for critical listening and audio applications where precision and tightness in the low end are priorities.



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