30 Oct, 2015 by Pioneer India

When things shake or vibrate, they make sounds we can hear in the world around us. Sound is invisible most of the time, but sometimes you can actually see it. If you see a speaker cone (diaphragm) when it is turned on, you can notice the cone moving up and down very quickly. Due to this rapid movement of cone the sound waves are generated. These sound waves get generated from both directions of the cone. These reflected waves bounce off the walls, floors, and furniture in your room and interact in many different ways, sometimes adding together and sometimes canceling out. You can dramatically alter the quality of the sound your speakers make by putting them in different places. You would have noticed how most speakers are built into wooden cases? That's not just to make them look nice: it drastically changes the sound.
The primary role of the enclosure (typically, a box) is to prevent sound waves generated by the rearward-facing surface of the cone (diaphragm) of an open driver interacting with sound waves generated at the front of the driver because the forward- and rearward-generated sounds are out of phase with each other, any interaction between the two in the listening space creates a distortion of the original signal as it was intended to be reproduced. Additionally, because they would travel different paths through the listening space, the sound waves would arrive at the listener's position at slightly different times; introducing echo and reverberation effects not part of the original sound.


Types of enclosure

The speaker enclosure (typically, a box) is critical. Any speaker will produce sound in any cabinet, but optimizing the relationship between the speaker and the enclosure is the key to good bass. Shaping the low-end (bass frequencies below 200Hz) is the reason for choosing a particular enclosure type.  Three major types of speaker enclosures are sealed, ported and bass-pass type.

1. Sealed (or closed) enclosures

Here’s how a sealed enclosure works. The back of the speaker is completely sealed off. The air inside the enclosure acts as a spring, which helps control the movement of the cone. When the speaker moves out, the pressure inside decreases, when the speaker moves in, the pressure inside increases. It helps to create a better control on the diaphragm leading to more accurate sound.
A sealed cabinet produces a deep base and more accurate sound. Sealed cabinets are much easier to design and build than ported enclosures and are typically smaller in size.

2. Ported (or bass reflex) enclosures

In the front of this enclosure is a hole (port) that equalizes pressure between the inside and outside of the speaker. When the diaphragm moves back into the speaker, it increases the internal pressure, which is funnelled out through the front port of the speaker. This action augments the sound waves traveling from the speaker and increases the efficiency tremendously.
A ported cabinet produces punchier sound. It is large in size and complex to design when compared to sealed enclosures.

3. Band-pass enclosures

Band-pass boxes are a special type of ported box designed for maximum slam. The woofer is mounted inside a dual-chambered box (one chamber sealed, the other ported), with the sound waves emerging from the ported side. The sound that comes out of the port is extra loud within a narrow frequency range. Because bandpass boxes are super-efficient within that range, they tend to boom. These enclosures are used for subwoofers.


Conclusion

Now, you can play ‘In-Pin-Out’to choose which kind of speaker enclosure you wish to use. With every enclosure comes a different sound effect and you can choose what you desire. Unfortunately, you can’t get all of these together. So, you can choose your kind according to your needs and where you have to use it. The diagram below will help you out.

- Precise, clean sound
- Compact, fits in more places

- More boom (works better with hip-hop, rap and R&B music)
- Harder to tune: use a subsonic filter on the amp for clear tones

- Louder at Specifically tuned ranges of frequencies
- Boxes are often large
- Used for subwoofers

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