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port length

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absami 
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Posted: August 08, 2009 at 5:50 AM / IP Logged  
when we calculate circular port length for our desired frequency on different sites does that include the thickness of the enclosure which is 0.75?
following are some links to calculate vent length
https://www.the12volt.com/caraudio/boxcalcs.asp
http://www./help/Articles.cfm?id=31
http://www.psp-inc.com/psp-inc.com/c...calculator.cgi
DYohn 
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Joined: April 22, 2003
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Posted: August 08, 2009 at 9:36 AM / IP Logged  
If you use the12volt's calculator, you input the material thickness and it does take it into account.
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absami 
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Joined: July 18, 2009
Location: Pakistan
Posted: August 08, 2009 at 9:47 AM / IP Logged  

DYohn wrote:
If you use the12volt's calculator, you input the material thickness and it does take it into account.

thats for the cylinder volume calculator.....i am talking about Round Port Length Calculator....the 4th formula....

DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: August 08, 2009 at 11:35 AM / IP Logged  
Well, since you manually enter the enclosure volume, you should enter only net volume for whatever you are building.
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absami 
Member - Posts: 17
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Joined: July 18, 2009
Location: Pakistan
Posted: August 08, 2009 at 3:45 PM / IP Logged  
so if i get a port length of 8 inch for tuning 33 hertz i would add 8 inch + 0.75 wall thickness = 8.75 or 0.75 wal thickness + 7.25 = 8 inches.....get my point?
stevdart 
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Posted: August 09, 2009 at 7:51 AM / IP Logged  

Got your point.  No, you don't add more length to the port because it goes through the baffle from inside to outside of the enclosure.  That length, the thickness of the baffle, is part of the calculated port length.  In your example above, the port is still 8" no matter how thick you construct the walls.  Just don't make them any thicker than 8"!

It will be easier for you once you start thinking of a port as "air" rather than thinking of it as a physical enclosure.  While the port is the actual air itself and has its own dimensions and volume, the port structure is the total air / enclosure that is specific for port function and displaces volume from the box.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: August 09, 2009 at 10:29 AM / IP Logged  
Yes, sorry I misunderstood your question.  Port length is always the total inside length of the opening from front to back and has nothing to do with how it is constructed.
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absami 
Member - Posts: 17
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Joined: July 18, 2009
Location: Pakistan
Posted: August 09, 2009 at 1:09 PM / IP Logged  
great! thank u so much people....next question coming up in another thread port length - Last Post -- posted image.

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