SUBWOOFER BOX TYPES:

Sealed Sub Enclosures This seams to be one of the most popular subwoofer box used in SPL competition because it produces great low level power handling and require less space than most other speaker boxes need. The sealed box is the most forgiving to design errors. Now a couple of he cons of sealed boxes. You may notice more distortion at high frequency and the speaker magnet will not cool as easily as non sealed boxes. Now even though sealed boxes require the least amount of space if you have even less space than need for you sealed box for a give subwoofer you can use the Isobaric setup. This setup requires less air space in the sealed box but takes two subwoofers to get the output as if you had the one subwoofer in the correct sealed box. Isobaric is when you have a speaker mounted in a sealed box like normal but also mount another subwoofer to the first face to face. Vented / Ported Boxes / Bass Reflex If you are going to be making your own sub box, the bass reflex boxes are not nearly as forgiving as the sealed box and you will hear you design mistakes. The bass reflex or ported box is basically a sealed box with a port or vent tuned to a specific frequency. This setup has good power handling and excellent efficiency. Now the down side of the Ported box. The ported boxes can be much larger than sealed boxes. Playing a subwoofer below the tuned frequency and power handling will produce a very poor sound and will damage the subwoofer. Do not lower the port below the manufacturer’s recommended frequency, this will only make things a lot worse. An enclosure with a port tuned to a specific frequency. There is no internal pressure working against the speaker, giving it worse transient response and speaker damping than a sealed enclosure. It is more efficient (more sound) than sealed enclosures because the back waves are channeled into the listening environment along with the front waves. The ports in these enclosures help produce deeper bass up to the tuned frequency. Below the tuned frequency power handling is bad and damage to the woofer is likely to occur. Also, prefabricated boxes are not built with ports tuned to each speaker manufacturer’s recommendations and may sound muddy or sloppy depending which speaker is used. The air exiting the ports sometimes produce a medium to loud noise called port noise (speaker farts). Pros: • more efficient than sealed enclosures (higher sound output) • will generally have a better low frequency extension for a given response (up to tuned frequency) Cons: • larger than comparable sealed enclosure • poor power handling below tuned frequency making it easier to damage subwoofer • reduced transient response • ports on pre-fabricated boxes are not generally tuned to speaker manufacturer’s recommendations and sound can be muddy/sloppy • possible port noise (speaker farts) Bandpass Sub Enclosures The most popular in SPL competition. A bandpass box is basically a port box with another enclosure mounted to the front of it with another port or vent. When built correctly will produce very high SPL. But here is the problem. Bandpass subwoofer box is not for giving at all. If the box is not built correctly it will a total waste of time and money and sound horrible. Bandpass boxes have to be tuned for a narrow bandwidth of frequency response. Suboofers are susceptible to cone over-excursion for frequencies outside of the tuned frequency response, and even worse if below. Please make sure to use a very good crossover to keep the frequency response in the correct range. A bandpass enclosure is basically a combination of a sealed and vented enclosure. “A bandpass enclosure can sound good and give you a flat response but most of the generic bandpass enclosures are not designed for a flat response. They are designed to impress you in the stores. This means that they are built to produce a large peak at some frequency near 60hz. These enclosures will work well with something like rap music but generally won't sound good with other types of music. If you use a bandpass enclosure, it should be designed specifically for your speakers” Pros: • Great power handling • Good low frequency response Cons: • Not as efficient as vented enclosures • Ports are not tuned to speaker requirements • Most speakers will sound better in ported or sealed enclosure Polyester Fiber Fill - is used to slow down back waves from a speaker inside the box, making the subwoofer perform as though it were in a bigger enclosure than it is really mounted in. It is recommended to use approximately 1 pound of fill per cubic foot of box volume. In enclosures were it is possible for fill to blow out of port a light multipurpose adhesive should be used to secure the fill to the wall linings.

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