The Ported, or Vented Subwoofer Enclosure.

The Vented, or Ported Subwoofer Enclosure is the most common design in use today. High efficiency and low-end response that rattle your fillings make it so - but is it the best sub box for your system? Consider these facts:


Advantages:

• Efficient - Speaker cone movement is greatest for a given input signal
• Tuning port allows contouring of frequency response
• Bass response and boost from port tuning can be thunderous

Disadvantages:

• Speaker is not damped by box, so bass is not quite as accurate
• Improper port design can annihilate a speaker well under its RMS power rating
• Response curve is usually nonlinear at port tuning frequency

The vented or ported subwoofer enclosure is best suited to electronic music such as rap or electronica where punchy, responsive bass is not as important as deep-reaching, longer bass notes are. Vented enclosures are also best when you don't have as big an amp as you'd like. As the most efficient sub box design, a ported enclosure will give you a higher spl per watt than other designs.

One must be cautious selecting drivers, when buying a prefabricated vented subwoofer enclosure: If the resonant frequency of the box is not well matched for the subwoofer driver you select, uncontrolled resonance can ruin your sound quality or even destroy your subwoofer. If you are driving the sub with nearly its maximum recommended power, be cautious using a ported box and pushing the sub to its limits. The enhanced output the vented subwoofer enclosure design offers may well cause your speaker cone's excursion to go beyond its design - causing mechanical noise and eventually destroying the subwoofer.

The subwoofer cone can begin wildly oscillating, moving far more than it ever would based on amplifier power alone. While this makes for some impressive youtube video, it is not good for your speaker or sound quality. Some speakers simply won't work in some ported boxes.

It is best to consider the size box you are willing to accomodate, then select a driver that works well in a vented enclosure of that size. All decent websites list this information for the drivers they sell - or, visit the manufacturer's website and look for the specifications for your subwoofer there. Finally, after deciding on a driver, use either the manufacturer's specifications for a ported enclosure, or download the software from the links on this site to design your own. When using the freeware sub enclosure tools, graph the frequency response of the sub and enclosure combination, and make any necessary alterations to keep the resonant response from sending your cone into orbit.



Typical Ported (Vented) Enclosure Volumes for Common Subwoofer Sizes 6.5-inch Subwoofer Driver
ranges from .2 cu ft - 1.0 cu ft

8-inch Subwoofer Driver
ranges from .4 cu ft - 1.5 cu ft

10-inch Subwoofer Driver
ranges from .6 cu ft - 3.5 cu ft

12-inch Subwoofer Driver
ranges from 1 cu ft - 6 cu ft

15-inch Subwoofer Driver
ranges from 1.5 cu ft - 8 cu ft

Deciding which type of subwoofer enclosure to build

The type of enclosure you use will have a dramatic impact on the performance of your car or home subwoofer. It's important to understand the three major types of subwoofer enclosures, and how they affect subwoofer driver performance.


The two first factors to consider when deciding on what type of sub box to buy or build are:

• Do I want the best possible sound or the loudest, lowest bass notes, and
• How much amplifier power do I have, and how close to the speaker's max is it?

Sound Pressure Level vs. Sound Quality Designs

SPL designs typically use a vented, or ported, enclosure. By tuning the port to the resonant frequencies of the speaker cabinet and subwoofer driver, low frequency response is boosted and optimized at what is known as the "port tuning frequency".

SQ Designs typically use a sealed subwoofer box enclosure type. This is because the sealed sub box provides damping - meaning, the sealed design helps control the motion of the speaker cone, causing its movement to follow the input signal more closely. The result is more accurate bass - the tradeoff is less efficiency.

The bandpass subwoofer enclosure attempts to enhance bass response and cancel out higher frequencies using a combination of port tuning and a driver that fires into another chamber rather than into the listener's airspace. They are more complicated, but offer distinct advantages in certain situations if well designed. These sub boxes offer the lowest bass response - and the most nonlinear. Amazing if done right - but horrible if they aren't built to tight specifications.