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[How To] Design a ported box
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<blockquote data-quote="seth350" data-source="post: 1280537" data-attributes="member: 559168"><p>Now for the other part of my write up....</p><p></p><p><strong>Slot Ported Boxes</strong></p><p></p><p>Ported boxes are similar to sealed boxes in the way you calculate the airspace.</p><p></p><p>You still start out finding out how much cuft you need and then going from there.</p><p></p><p>Lets begin.....</p><p></p><p>Lets say your sub needs 3.5cuft ported and you want it ported at 33hz.</p><p></p><p>You first begin by finding what measurments will give you 3.5cuft.</p><p></p><p>To calculate for cuft, read my other article for instructions on how to do it.</p><p></p><p><a href="http://forums.caraudio.com/vb/showthread.php?t=128157" target="_blank">http://forums.caraudio.com/vb/showthread.php?t=128157</a></p><p></p><p>WxHxD</p><p></p><p>34"x18"x13" = 3.56cuft Close enough!</p><p></p><p>Ok you have your dimensions, and your net volume now time for the port.</p><p></p><p>I recommend using a program like WinISD for this. Its quick and easy to do.</p><p></p><p>Punch in the parameters and we get this....</p><p></p><p>WxHxL</p><p></p><p>3"x18"x30.5" = 33.66hz</p><p></p><p>Now you have decided on how big of a port you want. Now its time to calculate its displacment.</p><p></p><p>#1 What you do is you take the length (30.5") and substract .75 from it. = 29.75</p><p></p><p>#2 Then you multiply that by your height (29.75x18=535.5)</p><p></p><p>#3 Then take your width (3") and add .75 it (3.75) then multiply by what you got in step #2.(535.5x3.75=2008.125)</p><p></p><p>#4 Now take the number you got from #3 and divide it by 1,728 (2008.125/1,728=1.162109375) then do significant figures and you get 1.16cuft.</p><p></p><p>Now you have your port displacment and now you need your sub disp.</p><p></p><p>Lets say your sub needs .18cuft displacment.</p><p></p><p>Ok now here is what you do.</p><p></p><p>Take you net volume (3.56cuft) and add your port disp. (1.16cuft) and add your sub disp. (.18cuft) together and you get your gross volume which is 4.90cuft.</p><p></p><p>Now, you have to make adjustments to your dimensions in order to get 3.56cuft after you add the port and sub.</p><p></p><p>So now you take the measurments you started out with and adjust the height and width until you get 4.90cuft.</p><p></p><p>Which you should end up with 36.75"x18"x16" and that gives you 4.88053cuft and then do significant figures and you get 4.90cuft.</p><p></p><p>You dont change the height b/c then it would mess with the disp of the port and also cause it to change the tuning and it gets confusing from there. So do not change the height when adjusting your measurments</p><p></p><p>Now you build the box to those dimensions, not the dimensions you started out with.</p><p></p><p>You use the new measurments because then when you put in the port and the sub you have 3.56cuft left for the sub. Which is what it called for!</p><p></p><p>Now you have designed your own box and its done right! Hopefully........</p><p></p><p>Hope this helped out the noobs, and anyone else who needed it.</p></blockquote><p></p>
[QUOTE="seth350, post: 1280537, member: 559168"] Now for the other part of my write up.... [B]Slot Ported Boxes[/B] Ported boxes are similar to sealed boxes in the way you calculate the airspace. You still start out finding out how much cuft you need and then going from there. Lets begin..... Lets say your sub needs 3.5cuft ported and you want it ported at 33hz. You first begin by finding what measurments will give you 3.5cuft. To calculate for cuft, read my other article for instructions on how to do it. [URL="http://forums.caraudio.com/vb/showthread.php?t=128157"]http://forums.caraudio.com/vb/showthread.php?t=128157[/URL] WxHxD 34"x18"x13" = 3.56cuft Close enough! Ok you have your dimensions, and your net volume now time for the port. I recommend using a program like WinISD for this. Its quick and easy to do. Punch in the parameters and we get this.... WxHxL 3"x18"x30.5" = 33.66hz Now you have decided on how big of a port you want. Now its time to calculate its displacment. #1 What you do is you take the length (30.5") and substract .75 from it. = 29.75 #2 Then you multiply that by your height (29.75x18=535.5) #3 Then take your width (3") and add .75 it (3.75) then multiply by what you got in step #2.(535.5x3.75=2008.125) #4 Now take the number you got from #3 and divide it by 1,728 (2008.125/1,728=1.162109375) then do significant figures and you get 1.16cuft. Now you have your port displacment and now you need your sub disp. Lets say your sub needs .18cuft displacment. Ok now here is what you do. Take you net volume (3.56cuft) and add your port disp. (1.16cuft) and add your sub disp. (.18cuft) together and you get your gross volume which is 4.90cuft. Now, you have to make adjustments to your dimensions in order to get 3.56cuft after you add the port and sub. So now you take the measurments you started out with and adjust the height and width until you get 4.90cuft. Which you should end up with 36.75"x18"x16" and that gives you 4.88053cuft and then do significant figures and you get 4.90cuft. You dont change the height b/c then it would mess with the disp of the port and also cause it to change the tuning and it gets confusing from there. So do not change the height when adjusting your measurments Now you build the box to those dimensions, not the dimensions you started out with. You use the new measurments because then when you put in the port and the sub you have 3.56cuft left for the sub. Which is what it called for! Now you have designed your own box and its done right! Hopefully........ Hope this helped out the noobs, and anyone else who needed it. [/QUOTE]
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