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why is port diameter important?


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rfhvhtoo 
Copper - Posts: 238
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Posted: January 26, 2010 at 1:36 AM / IP Logged  
Why do people suggest larger port diameters? when you can get the same tuning with shorter length at smaller diameters and less displacement?
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Steven Kephart 
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Platinum spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spaceThis member consistently provides reliable informationspace
Joined: November 06, 2003
Location: Oregon, United States
Posted: January 26, 2010 at 2:54 AM / IP Logged  
Because a smaller port diameter will have higher air speeds to allow for the same amount of air to flow. Higher air speeds in the center along with friction along the walls of the port and the resultant slower air speed in that area cause a chuffing sound. That is also known as port noise.
kanarrjl 
Member - Posts: 30
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Posted: January 26, 2010 at 9:04 AM / IP Logged  
also because up to a point (depending on your application) it will increase your spl numbers.
incognyto 
Copper - Posts: 64
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Posted: January 26, 2010 at 9:12 AM / IP Logged  
Now knowing this is it possible to make a box specificly for spl but make it easy to convert it to sq??? Swap tube ports legnths??
kanarrjl 
Member - Posts: 30
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Location: Michigan, United States
Posted: January 26, 2010 at 9:16 AM / IP Logged  
incognyto wrote:
Now knowing this is it possible to make a box specificly for spl but make it easy to convert it to sq??? Swap tube ports legnths??
generally a spl setup is about 16square inches of port face area to every square foot of box space and is tuned high (50-70hz) and a sq setup is around 10square inches of port and tuned low (25-35hz)
incognyto 
Copper - Posts: 64
Copper spacespace
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Posted: January 26, 2010 at 9:21 AM / IP Logged  
So with that I can build a box for spl with a large port and Maybe have a divider in thAt port so part of it could be split off and sealed making the port area smaller?? Or would the lenth have to change also???
kanarrjl 
Member - Posts: 30
Member spacespace
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Posted: January 26, 2010 at 9:56 AM / IP Logged  
to some extent that may work it depends on your aplication give me some numbers then i could help you out
incognyto 
Copper - Posts: 64
Copper spacespace
Joined: December 26, 2009
Location: British Columbia, Canada
Posted: January 26, 2010 at 12:20 PM / IP Logged  
I have the PDF at home for the ts
parameters but it's fir the 15" alpine type r
Swr-1542d
I have 2 of them And I put them in my box that I made fir my jl audio 12's to jl specs I'll post those dimentions too bit apparently it's 3.5 cubic feet total when I measure the box I get 5.5 without takin the ports out of the measurement
rfhvhtoo 
Copper - Posts: 238
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Location: Florida, United States
Posted: January 27, 2010 at 1:59 AM / IP Logged  
im getting the calculation on carstero.com that I should not have a port Diam less than 7.69inches. done this mean that 2 4inch Diameter ports give me 8 inches in Diamter of port?
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kanarrjl 
Member - Posts: 30
Member spacespace
Joined: September 23, 2006
Location: Michigan, United States
Posted: January 27, 2010 at 8:27 AM / IP Logged  
rfhvhtoo wrote:
im getting the calculation on carstero.com that I should not have a port Diam less than 7.69inches. done this mean that 2 4inch Diameter ports give me 8 inches in Diamter of port?
No. 1-4" port is 12.56 square inches. Then take that x2 and it gives you what 2 of them would be 12.56x2=25.12 where as 1-8" port is 50.26 square inches. Basically you would need 4-4" ports.
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