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to port a sealed box....

Old 01-03-2004, 03:50 PM
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hey guys. i got a shaker 15" (yea shaker i know...) in a 2.75cuft sealed box. would i just be able to stick a 4" port in this box tuned to 25hz?? i think 2.75cuft is large enoguh isnt it? maybe two 3" ports? or even two 4" ports...thanks
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Old 01-03-2004, 04:43 PM
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just port it, then fill it with compressed air...it will get more air in the box, thus raising the amount of cubic feet of air inside.
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Old 01-03-2004, 04:47 PM
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what he said, but only up to 60 psi, or else you raise your sound stage..
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Old 01-03-2004, 05:02 PM
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hahaha if only...seriously though...2.75cuft is too small for a ported 15 to 25hz?
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Old 01-03-2004, 05:07 PM
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I donít know about this... I heard a rumor Dukk was sealing all his ported enclosures... I think it was something about compressed air and a blown mind [img]graemlins/freak.gif[/img]
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Old 01-03-2004, 06:08 PM
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Actually, he's sealing the boxes, removing the dust caps from the sub and putting a lightweight port in through the dustcap.
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Old 01-03-2004, 09:16 PM
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For a 15" you will want a bigger box or a box tuned higher.

If you really want it tuned to 25hz one 4"ID x 16.5"L port will do it

Perhaps tune it to 35hz instead for a more reasonable curve for the box size. Then you can use 4"ID x 7"L port.

Post all the information you have on the sub and we will be able to help find whats best for you.
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Old 01-03-2004, 09:35 PM
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its ok i have winISD. so the disadvantage to a smaller ported box is a worse curve?
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Old 01-03-2004, 10:00 PM
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A smaller box won't allow the woofer to extend into the lower frequencies as easily. Depending on what you want it to do youmight be better off keeping it sealed (ie a smoother curve or deeper bass response) But if you are looking for SPL you could tune the box to 45 hz and have a huge hit at 45hz that would be way more powerful than any sealed box.

Since you have WinISD, I guess that it is up to you as what you want - do you want the deep 'thunder' at the expense of volume, or do you want loud bass hits with weak 'thunder'

Play with all sorts of tuning frequencies - but remember if you tune it low and have really long ports the volume of the ports will have to be subtracted from the volume of the box unless you make external ports (JVC minisystems)

Remember, not much music plays below 40-35 hz, so don't shoot for lower than that unless your planning on listening to thunder tracks regularly.

Or, start from scratch and build a new box to your liking.
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