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conig
Dodge Dakota
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1/24/2003
13:14:18

Subject: porting sealed box. how to calc ports?
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As of present I have an rt enginering box with an internal volume of 1.75 per sub. the link for the box is here http://www.sounddomain.com/sku/RTE32312

I want to try porting my box to get some more bass out of it. for my subs x-tant x series dual 4 ohm subs the ideal size of a ported enclosure is 2.00cf and the alternate boxes with spl gradually getting lower is for larger boxes.
the tuning frequency for the 2.00 ported box is 32hz and the port size it shows is 4x15. for a net volume of 1.81cf includeing port and driver.

I don't really want to take on the task of building a whole new box my question is can I port the box I have? also I have been looking at equations for tuning ports but can't figure out how to calculate it. the ports I'm thinking of useing are either 3x12 or 4x12. If I port this box will it still sound ok? which size port should I use? how about square ports?

all info is as always greatly appreciated.



conig
Dodge Dakota
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1/24/2003
18:21:16

RE: porting sealed box. how to calc ports?
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never mind remeasured my box size is 1.25.

the optimim sealed size is 1.00 can I add like a small box or something to the inside to take out some of the airspace.



silverD
Dodge Dakota
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1/24/2003
18:52:33

RE: porting sealed box. how to calc ports?
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Conig
What kind of sound are you after? A sealed box will give you better sound quality than a ported, but the ported will be louder than the sealed near the tuning frequency. The port will add more "boomyness" to the bass. Although people say that square ports have less distortion, PVC pipe cut to the right length works very well. The pipe diameter and length are determined by the subs T/S parameters (Qts, Fs, Vas....etc) and box volume. Tuning can be a long task to get it just right. If it is off by a few Hz, you can introduce peaks of output at certain frequencies. If you are willing to cut up your box to make it ported, keep in mind it may sound worse. Do you know if anyone else has used these subs in ported boxes? I'll check out the subs and let you know if it is a good idea with the box you have. If you want to make your box have less volume, put scrap pieces of wood, brick, or anything dense. Make sure you measure its volume and subtract it from the box volume.

Any more Q's let me know,
Nate



silverD
Dodge Dakota
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1/24/2003
19:34:09

RE: porting sealed box. how to calc ports?
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I found some info on suggested applications:
www.xtant.com/html/techSupport/pdfs/X1244.pdf

Here is what I came up with:
Because the Qts of the subs is near 0.5, the woofer is best suited for sealed use. 0.4 and lower is when ported is the best option, and above .65 infinite baffle. The box should be at least 2 ft^3 for this sub to be ported to get good sound. Since yours is 1.75 or less, I wouldn't suggest porting. Although porting would be possible, I find that the required port length is too long for your box. I found that a tuning freq of about 34Hz would work with a 1.75 ft^3 box with a square port that is 3.25" x 2.66" and 9" long, or a 3.25" diameter pipe that is 8.25" long. This would produce a bad peak in output though. I would say stay with the sealed box.
Nate



conig
Dodge Dakota
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1/26/2003
16:02:16

RE: porting sealed box. how to calc ports?
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thanks for the help man. I think I'm just going to get some new subs.



Gabe
Dodge Dakota
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3/16/2003
20:15:46

RE: porting sealed box. how to calc ports?
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Hey, i know it's probably a little late but, for reference a site with the math for the port tuning is diysubwoofers.org . I had the same question you did and ended up finding this info in the diy site ported section. Good Luck



conig
Dodge Dakota
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3/17/2003
13:21:03

RE: porting sealed box. how to calc ports?
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yeah I found that site a while back. I just built a new box about a month back but Im about to build another one again as the one I have now leaves no practicality to the rear seat.



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