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| By: mycarjams.com on Sat, 4 Oct 00:03:20 -0500
| | Lots of enthusiasts argue the benefits of each every day, but they do so with uneducated facts. Here I won't give the advantages and disadvantages of each, rather just give facts as to what each does. This way one can draw their own conclusions as to which they would rather use.
For those who don't know what these are, here is a little refresher. The two most common enclosure types that are used in audio systems are ported (or vented) and sealed (or air-suspension or acoustic-suspension). A sealed enclosure is simply that where the entire enclosure is airtight, with no vents or holes of any kind. This is what you will commonly see people using, as they have not built their own and are using a pre-fabricated box. Sealed enclosures tightly regulate the suspension of the woofer, as the air inside the box is always trying to equal its pressure to that of the atmosphere.
Typically, the bigger the enclosure is, more low-end output is produced at the expense of the amount of power that can be allocated to the woofer. The larger box limits throw less, and excursion is increased. This results in an overall lower box Qtc (Q quotient), which is a more advanced topic I will discuss later.
The smaller a sealed enclosure is, the more controlled the woofer's stroke is. Driver excursion is limited, and response is generally more punchy. Because of this limit in excursion, more power can safely be allocated to the woofer through means of an amplifier.
A ported enclosure is that which is "tuned" to a specific frequency within the frequency range. This tune usually ranges anywhere from 25 Hz all the way up to 50 Hz, which is the optimal range for producing bass. This tuning is accomplished by means of a port, which acts as a bass reflex to amplify the sound produced. This port utilizes the rear sound waves that come out of the back of the subwoofer, thus effectively increasing output, among other things.
This kind of enclosure is tuned by adjusting the dimensions of the port in relation to the internal net volume of air inside the box. This change is affecting the way the port resists motion, thus tuning the box. Tuning a box in this way however, does limit the frequency range where the most output can be achieved. When the factors are put together, the rear waves from the subwoofer are delayed so that the front waves and the port waves are constructive and compliment each other.
Designing a useful ported enclosure is much more complicated than a sealed, so making one is usually only for experienced enthusiasts who have calculated the factors correctly. However, doing so can cause a large increase in output over the main frequency range of bass, usually 3-6 decibels.
Some people like to claim that one enclosure type is better than the other, but this is just not true. Both have their ups and downs and in-betweens.
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