Now we will start with :

Sealed enclosures : A SEALED enclosure will be the smallest,and is the simplest of enclosures and will have good low frequency extension, but might not have the best low frequency extension. If space is limited.

and its a good choice for SQ fans (Sound Quality).

PORTED enclosures (Bass Reflex) : A PORTED enclosure will generally have a better low frequency extension for a given response shape,but would require a larger enclosure. If you made the enclosure as small as the sealed enclosure, but ported it to gain the low frequency response, the output would deviate from the desired flat response.

Ported enclosures are slightly more difficult to design than a sealed enclosure. When using a sealed enclosure, it is difficult to be so far off as to risk damaging the woofers. In any type of enclosure, the woofer relies on the enclosure for damping. If there is insufficient damping, the woofer's cone will move significantly more than it should. The ported box will provide virtually no damping below the port frequency, all of the control will be provided by the woofer's suspension. Below the tuning (port) frequency, it is possible to cause damage to the woofer well before power levels approach the maximum power ratings of the woofer.

common tunning frequencies :

Sound Quality : 20 up to 28 Hz.

Sound Quality Loudness : 30 up to 35 Hz

Sound Pressure LeveL SPL : 40 up to 80 Hz (test tones are played rather than normal music, to avoid Low frequencies, which damages the speaker).

Its commonly used for competition propose. and not everyday driving.(unless you like listening to test tones for everyday driving).

BandPass enclosures (Single Reflex): Bandpass enclosure can sound good and give you a flat response,but most of the bandpass enclosures(in the market), are not designed for a flat response, this means that they are built to produce a large peak at some frequency from 50 to 60 Hz, these enclosures will work well with Rap, but generally they dont sound good with other types of music.

if u use a banpass enclosure. it should be designed specificaly for your speaker.

P.S : its not always recommended.

check attachment below

-hope that this info will help many to understand the different types of enclosures. and which type is better for their propose.

-zAK.

A bandpass enclosure should NEVER has the ports at that angle (sub firing straight into the port(s))... Always at least 90 degrees

thnz for info

and yes i 've seen bandpass, and yes 90 degrees

I'd make it like this ...

i like the colours

I would say that the meat of the post dealt with glaring generalities that do not stand up to real world scrutiny. First, what is your definition of low frequency extension? 30 Hz? If so then I have yet to see a sealed subwoofer system that could not hit 30 Hz in the car. Tuning in the 20's may sound horrible depending on the sub. It could also end up less efficient than a sealed enclosure for the same sub. Depending on the sub, you might need to tune it to the high 30's or even into the 40's to get the smoothest response from it. Also depending on the sub, you may not be able to get it to sound good in a sealed enclosure at all. If the sub wants a mid 30's tuning for best response it will have poor low frequency extension as the sub will not produce usable output below tuning. Until you talk specifics, you can't make a statement about the SQ of a particular enclosure type or tuning as it will depend totally on the sub installed in the enclosure.

A bandpass enclosure should NEVER has the ports at that angle (sub firing straight into the port(s))... Always at least 90 degrees

Can I ask why?