SEALED vs PORTED (basic info.)

I do have a question...I'm looking at a dual 12" vented enclosure tuned at 34Hz. it has one 6" vent port on one side and no divider and it is built very stout double baffle and all. Does it matter that there is no divider (seperate chambers)? Also can someone tell me does it matter if inside of the enclosure that the corners aren't rounded (curved)? i heard that the bass is smoother if the corners and the port is curved.....The enclosure is 5 cubic ft......Thanks for your help in advance!! OH YEAH....the specs. on my kicker comps are:sensitivity 89.1 db......frequency response 27-500 Hz. ...recommended rms power 150 watts....peak power 300 watts...Impedence 8 ohms......Someone please give me some good answers \m/

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Originally Posted by squeak9798

I think you may have your terminology a little off there, or I am reading it wrong. The ported will have greater low frequency output down to the tuning, but a sealed with a decent Qtc will have greater low frequency extension (i.e. sealed can play lower than a ported box, but down around the tuning frequency the ported will have greater output).


Also a good time to mention Hoffman's Iron Law:

You can only have two of the following three at any one time;

1) Small Box
2) High Efficiency
3) Low frequency extension

If you want any two of them, then you must sacrifice the third.

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Sealead bloxes have less group delay, which means it has a more linear response on the rolloff. Like a 6db/octave highpass xover vs a 12db one for example, so it "sounds better".

Anyway, you can sacrifice a little output at tunning for a lower extension, you can get the extension very low like 20hz, which is good.

Depends on the sub, competition subs with an fs of about 46hz, and a low Qts will almost need to sacrifice efficiency for the extension.

Ported boxes have MUUUUCH less distortion for high SPL applications on music vs sealed, for sure. Or atleast around tunning.

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Originally Posted by Gilgamesh

I do have a question...I'm looking at a dual 12" vented enclosure tuned at 34Hz. it has one 6" vent port on one side and no divider and it is built very stout double baffle and all. Does it matter that there is no divider (seperate chambers)? Also can someone tell me does it matter if inside of the enclosure that the corners aren't rounded (curved)? i heard that the bass is smoother if the corners and the port is curved.....The enclosure is 5 cubic ft......Thanks for your help in advance!! OH YEAH....the specs. on my kicker comps are:sensitivity 89.1 db......frequency response 27-500 Hz. ...recommended rms power 150 watts....peak power 300 watts...Impedence 8 ohms......Someone please give me some good answers \m/

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that box is a bit too big for those subs FYI...3-3.2 is about the biggest i would go for them...

but.... the shared chamber design is a plus.. it lets both subs compress the same air space and helps control the cone movement..which in turn increases the output..it also reduces the required airspace by about 10% - 25% per sub... IE. if each sub needs 1 cf each then the 2 same subs in 1 shared space would only need 1.5-1.8cf..

almost all my boxes I do are shared space and i also do not round the interior corners unless the customer wants to pay the extra for it... the dif in sound at high volumes is negligable at best and I am positive no one can "hear" the difference...

After hearing my new ported setup, I will never do another sealed one

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Originally Posted by bigbang

A sealed box rolls off at about 12db/octave below f3, relatively shallow, whereas a ported box rolls off at about 18-24db/octave past f3, pretty sharp. The sealed box will give you alot of usable bass in the very low range, mid 20's and down, where in most automotive ported boxes, this low bass would be diminished or absent. A sealed box almost certainly gives you a smooth frequency response unless built too small, in which you will start gaining a midbass peak, so from a musical standpoint, they sound good because they are predictable, and you won't have a narrow band of a frequencies that are way too loud, or one-note-bass as in the case of a ported box tuned for output. The benefit of the ported box, besides output, is extra energy in the low frequencies, but I wouldent say they play lower. If you design a ported box for low frequency extension, not SPL, you can choose a sub and box to give the system an almost flat response, down to the port tuning frequency, where it drops sharply. In my opinion; a ported box tunned high for SPL. For the flattest response, a ported box tuned low with the correct sub. For the absolute lowest sub-bass frequencies or inaudible notes, the large sealed box. And as for group delay...

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Just browsing the thread getting ideas...ran across this thread. What if a sub is recommended for a sealed enclosure, but you graph a flat response by tuning ported and still get the low extension? I am working on a f3 of 27 which gives me a roll-off at 29, but I am not concerned about hitting any notes lower than 33hz noticeably.

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Originally Posted by soldiermedic

Just browsing the thread getting ideas...ran across this thread. What if a sub is recommended for a sealed enclosure, but you graph a flat response by tuning ported and still get the low extension? I am working on a f3 of 27 which gives me a roll-off at 29, but I am not concerned about hitting any notes lower than 33hz noticeably.

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What sub? With what you described you should be fine. F3 of 27hz is quite nice, and will play nearly anything you throw at it.

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Originally Posted by RAM_Designs

What sub? With what you described you should be fine. F3 of 27hz is quite nice, and will play nearly anything you throw at it.

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It's an Infinity Perfect DVQ 12" with the mid insert, and it is recommended for a sealed box. But graphing it, I am seeing too much roll at too high of a frequency. However, when I played with it in WinISD and bass box pro, I got to a nice place on my graphing that gave me the f3 of 27, putting the tuning down to 18hz in a 2.5cf box. I know it seems a little extreme, but I get a flat response from 25hz on up, and I can get plenty power to the sub.

i have a 1979 ford F-150 rag cab and im going to build a box for my p1222 jbl but i do not know if i should got ported or sealed i have 9 inches from floor to back of seat and it can be 16 inches tall and has 5 inches of room at the top from back cab wall to seat with about a 2 inches inbetween seat and the box but what kind of box should i build?

thanks for the help

oh and the box can be long ill get the exact mesurement if needed and i will power the sub for now off of a kenwood 800/800 thats until i can get me more power :P

These questions were asked that I am interested in, but were never answered.

- Does the port location make much difference? I.E. front firing, top firing, rear firing or side firing
- Does the port need to be a least one port diameter away from the box wall sides, rear wall and edge of sub? (does placement matter? How?)
- Okay... how do you determine what a box is tuned at?
- Also if a box is sealed does that mean it is not tuned?
- If not with a sealed box does different size sealed boxes sound better than others? (How does the size of the sealed affect the sound, regardless of specs?)

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Was unsure if I could use a ported box in my truck know I know my answer. Helpful thread. Thanks