Is there a forumla for changing from vents to ports? - AVS Forum
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post #1 of 7 Old 06-17-2014, 02:25 AM - Thread Starter
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Is there a forumla for changing from vents to ports?

I have an extremely nice enclosure that I'd like to use but my new sub requires 0.38 ft^3 for it's vent which basically makes this this box useless because it's too small when you add .38ft^3! I'm from the old school and have never used a vented box, only sealed and ported. Is there a way to find a proper port size instead of a vent or do these new subs require vents and porting is a thing of the past?

Thanks guys!

Edit---I can convert the volume of a cube to the volume of a cylinder, that is not the issure...I am just wondering if the cyinder port differs in some way from a vent, ie less?

Last edited by functionalfool; 06-17-2014 at 02:49 AM.
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post #2 of 7 Old 06-17-2014, 06:08 AM
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Originally Posted by functionalfool View Post
I'm from the old school and have never used a vented box, only sealed and ported.
Vented and ported are the same thing.
For calculating speaker enclosure dimensions use WinISD.
http://www.linearteam.dk/default.aspx?pageid=winisdpro

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post #3 of 7 Old 06-17-2014, 07:41 AM
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Originally Posted by Bill Fitzmaurice View Post
Vented and ported are the same thing.
For calculating speaker enclosure dimensions use WinISD.
http://www.linearteam.dk/default.aspx?pageid=winisdpro

This brings up a speaker design question. Are these calculations aimed at creating the smallest possible box or at creating the exact size for best performance?
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post #4 of 7 Old 06-17-2014, 08:47 AM
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This brings up a speaker design question. Are these calculations aimed at creating the smallest possible box or at creating the exact size for best performance?
The program will default to the flattest possible response and lowest possible extension for the given driver specs. In the event that the default cabinet size is too large you can alter the box size and, in the case of a vented enclosure, tuning. But where going smaller than optimal is concerned Hoffman's Iron Law always constrains the result.

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post #5 of 7 Old 06-19-2014, 02:38 AM - Thread Starter
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Originally Posted by Bill Fitzmaurice View Post
Vented and ported are the same thing.
For calculating speaker enclosure dimensions use WinISD.
http://www.linearteam.dk/default.aspx?pageid=winisdpro
How is this possible? It would take a 4inch diameter cylindrical port of 53 inches long to equal that large of a volume! Volume of a cylinder is V=h*pi*r^2 ---> (55*3.14*2^2)= 665.7 inches, converting to ft you dived by 1728 which equals 0.385ft^3 (ideal vent size per manufacturer). This vent is virtually the size of a compact sealed enclosure! Am I way off here or missing something in my calculations?

I, personally, am not worried about size because this will be used in home audio so can be 6ft^3 if the specs called for that! I am just new to this vent thing, been 15 years since I bought a current model subwoofer before last weekend. I can absolutely make a vented enclosure with the long slit (vent) in the box but was hoping to use my old box is all.

Also, I am powering this with a dedicated amp that can handle 4 ohms and put out proper wattage so all that is left is the box.

Last edited by functionalfool; 06-19-2014 at 02:42 AM.
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post #6 of 7 Old 06-19-2014, 05:07 AM
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Originally Posted by functionalfool View Post
How is this possible? It would take a 4inch diameter cylindrical port of 53 inches long to equal that large of a volume!
The volume of a port/vent alone does not determine the Fb of the cab. Wherever you got that information from is incorrect. You also keep referring to vents and ports as if they were different terms. They are interchangeable. Suggested reading:
http://techtalk.parts-express.com/sh...Building-Bible

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post #7 of 7 Old 06-20-2014, 01:31 AM - Thread Starter
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Originally Posted by Bill Fitzmaurice View Post
The volume of a port/vent alone does not determine the Fb of the cab. Wherever you got that information from is incorrect. You also keep referring to vents and ports as if they were different terms. They are interchangeable. Suggested reading:
http://techtalk.parts-express.com/sh...Building-Bible
I'll give that a read and post back with any questions if I have any, thank you guys for all the info and help!
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