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Old 24th January 2004, 08:29 AM   #1
sma is offline sma  Indonesia
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Default enclosure port

anyone can help for port specification?.I want to build subwoofer enclosure the enclosure spec is 2.50 cu ft volume,port is 25sq inch X 15" Lenght....I don't understand about 25 sq",how i can convert that to normally round diameter inch?
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Old 24th January 2004, 08:33 AM   #2
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you can see if this helps

http://www.loudspeakers101.com/VentCal1.htm
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Old 24th January 2004, 08:41 AM   #3
sma is offline sma  Indonesia
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thank you,

i already try but i don't understand use this conversion.i input data,but the calculator can't process...i don't know what the mistake.

is the sq inch port mean not rounded ?
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Old 24th January 2004, 11:49 AM   #4
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To use that calculator you need to know what freq the port will tune your box to .
what dia tube is available to you to use such as plumbing pipe 3" or 4" plug them in & it will give you a length
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Old 24th January 2004, 04:47 PM   #5
Ron E is offline Ron E  United States
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square inch is a measurement of area
a circle with an area of 25 square inches is :
Area=pi*diameter^2/4
rearrange:
sqrt(4*Area/pi)=diameter
For your area of 25 square inches, the diameter is 5.64 inches, or 14.3 cm.

It is hard to make a round port a specific size, so you can scale your length, based on available port diameters.
L1/L2=A1/A2, where L1, A1 are the original length and area, and L2,A2 are the new length and area...
rearranging again, and Realizing that area is proportional to diameter squared, and entering your port data:
L2=15*(Diameter^2/5.64^2)

You input the diameter of the ports you can get, and from that you can get the new length.....
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