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Sealed vs Ported vs Bandpass Enclosures

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 Sealed vs Ported vs Bandpass Enclosures
topic by -Phase One- - 01-10-2007, 02:25 AM


Some question what is best. Hopefully this topic will help people understand more about sealed and ported enclosures.

Sealed is the smallest and the simplest of enclosures and will have good low frequency extension, but might NOT have the best low frequency. If space is limited, sealed would be your best choice. It's also the favorite type of enclosure for the SQ fans. (Sound Quality)

Ported will have 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, but ported it to gain low frequency response, the output would deviate from the desired flat response. They are also more difficult to build and need more space than sealed.

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

Common Tuning Frequencies
Sound Quality(SQ): 20hz - 28hz
Sound Quality Loudness (SQL): 30hz - 35hz
Sound Pressure Level (SPL): 40hz - 80hz (Test tones are played rather than normal listening music, to avoid low freq., which damages the speaker. It's commonly used for competition purpose only and not daily driving. Unless you like listening to test tones for your everyday driving music)

Bandpass enclosures can sound good and give you a flat response, but most bandpass enclosures (prefab) are not designed for a flat response. This means that they are built to produce a large peak at some freq. from 50hz - 60hz. These enclosures work well with rap, but they don't sound good with other types of music. If you use a bandpass enclosure it should be specifically designed for your sub(s).


Calculations & Formulas

dV = is the required diameter of port in inches
Fb = is the tunning frequency of the enclosure in hertz
Vd = is the volume displaced by the driver (woofer)
Lv = is the LENGHT of port in inches
R = is the internal radius of vent tube
Vb = is the internal volume of the enclosure cubic inches

To convert cubic feet into cubic inches
# cuft *1728 = value in cubic inches
Vd = Sd x Xmax
dV>/= 39.37*(Fb*Vd)^0.5
Lv = [(1.463*10^7R^2)/(Fb^2*Vb)] - 1.463
Value of R
R = square root (a/3.142)
and "a" is the area of square vent = Width*Hight

changing Round vent to Square vent
[CODE]A= Pi* (4/2)^2 [/CODE]
and Pi =3.142



8 comments for "Sealed vs Ported vs Bandpass Enclosures"

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 01-10-2007, 12:39 PMaway - #2
Jaiden05  space
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Originally Posted by -Phase One-
Some question what is best. Hopefully this topic will help people understand more about sealed and ported enclosures.

Sealed is the smallest and the simplest of enclosures and will have good low frequency extension, but might NOT have the best low frequency. If space is limited, sealed would be your best choice. It's also the favorite type of enclosure for the SQ fans. (Sound Quality)

Ported will have 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, but ported it to gain low frequency response, the output would deviate from the desired flat response. They are also more difficult to build and need more space than sealed.

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

Common Tuning Frequencies
Sound Quality(SQ): 20hz - 28hz
Sound Quality Loudness (SQL): 30hz - 35hz
Sound Pressure Level (SPL): 40hz - 80hz (Test tones are played rather than normal listening music, to avoid low freq., which damages the speaker. It's commonly used for competition purpose only and not daily driving. Unless you like listening to test tones for your everyday driving music)

Bandpass enclosures can sound good and give you a flat response, but most bandpass enclosures (prefab) are not designed for a flat response. This means that they are built to produce a large peak at some freq. from 50hz - 60hz. These enclosures work well with rap, but they don't sound good with other types of music. If you use a bandpass enclosure it should be specifically designed for your sub(s).


Calculations & Formulas
CALCULATIONS/ FORMULAS

dV = is the required diameter of port in inches
Fb = is the tunning frequency of the enclosure in hertz
Vd = is the volume displaced by the driver (woofer)
Lv = is the LENGHT of port in inches
R = is the internal radius of vent tube
Vb = is the internal volume of the enclosure cubic inches

To convert cubic feet into cubic inches





Value of R

and "a" is the area of square vent = Width*Hight

changing Round vent to Square vent
[CODE]A= Pi* (4/2)^2 [/CODE]
and Pi =3.142


Props on this post.
 01-14-2007, 11:07 AMaway - #3
King Allister 36 heat pts36 space
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LOL at posting Pi...
 02-04-2007, 06:33 AMaway - #4
bibbyboi 16 heat pts16 space
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Originally Posted by -Phase One-
Common Tuning Frequencies
Sound Quality(SQ): 20hz - 28hz
Sound Quality Loudness (SQL): 30hz - 35hz
Sound Pressure Level (SPL): 40hz - 80hz (Test tones are played rather than normal listening music, to avoid low freq., which damages the speaker. It's commonly used for competition purpose only and not daily driving. Unless you like listening to test tones for your everyday driving music)
Is this right?? I swear that spl uses lower freqs than sq.....
 02-04-2007, 01:54 PMaway - #5
GhosT  space
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^ no spl uses higher frequencies because they're more audible. lower frequencies are considered subsonic, you feel more than you hear. great way to find out what i mean is to pop in a bass cd that has test tones, go to normal listening volume and then compare 28hz to 45 hz. the 45 hz will be a hell of a lot louder
one
GhosT
 03-08-2007, 04:44 PMaway - #6
gweb63  space
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Hmmmmm

;) Very interesting....
 04-20-2007, 12:31 AMaway - #7
bdawson72  space
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Originally Posted by GhosT
^ no spl uses higher frequencies because they're more audible. lower frequencies are considered subsonic, you feel more than you hear. great way to find out what i mean is to pop in a bass cd that has test tones, go to normal listening volume and then compare 28hz to 45 hz. the 45 hz will be a hell of a lot louder
one
GhosT
I don't necessarily agree with this but its somewhat true. It has to do with a lot more than just that. Box Tuning and your specific sub have a lot to do with it. If you played a 65hz tone vs a 45 hz tone chances are that the 45 would seem louder to the average person.


Subsonic frequencies are actually those under 20hz because thats the range of human hearing even though it may vary from person to person.

Last edited by bdawson72; 04-20-2007 at 12:32 AM..
 04-20-2007, 12:44 AMaway - #8
GhosT  space
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generally speaking. i know it all depends on the subs and box, but overall the higher the frequency the louder compared to lower frequencies. also i never stated that all low frequencies are subsonic, i just stated "lower"

i will restate it though. lower frequencies are "less audible"

one
GhosT
 04-20-2007, 07:03 PMaway - #9
dcole18  space
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SPL has nothing to do with how audible the tone is... its easier to be louder with higher frequencies because the sub moves more air (with less excursion) this also makes it less of a load on the sub allowing it to handle more power... in most competitions 80-100hz is the highest freq. competitors are allowed to use.

the resonant frequency of the vehicle has alot to do with the frequency chosen to compete with as well...
 

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