8w7 port length

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kilj00y

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Joined: October 19, 2004

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Posted: October 20, 2004 at 11:17 PM / IP Logged

im in the prosess of designing a ported box for an 8w7 in a 1 cu. ft box and am looking at the diagram from jl for ideas. it reccomends a port (8.5" x 1.5" x 26"). my question is could i substitute a shorter port and just make it wider? or is just the width interchangeable (ie 7.5" x 2.5" x 26".

boxmaker85

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Joined: September 19, 2004

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Posted: October 20, 2004 at 11:23 PM / IP Logged

As long as the internal volume of the port is maintained then you should be good. I'm sure there is a limit but the sub is moving the same air mass in the port no matter how you change the shape of it.

kilj00y

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Joined: October 19, 2004

Location: United States

Posted: October 20, 2004 at 11:34 PM / IP Logged

so say i wanted a port 20 x 1.8 x 9 ... which all has roughly the same volume... just a different config. would that be the equivelant

stevdart

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Joined: January 24, 2004

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Posted: October 21, 2004 at 8:56 AM / IP Logged

http://www.carstereo.com/help2/Articles.cfm?id=31 is one of the tools found

here: http://www.carstereo.com/help2/Articles.cfm

"If you come up with a value too long for your enclosure, enter a smaller number(s) for the diameter, or the heighth/width of your vent(s), and click the "Calculate Length" button again to recalculate (you don't need to reload the page)." ___from the linked calculator.

First and foremost, keep the recommended box tuning frequency the same when you change port size.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

kilj00y

Member - Posts: 25

Joined: October 19, 2004

Location: United States

Posted: October 21, 2004 at 12:40 PM / IP Logged

i looked at that also. but the jl specs reccomend that port size, but it doesnt seem to match any of the calculators ive found. they claim its based off "actual tests and measurements" and not a calculator.

DYohn

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Posted: October 21, 2004 at 2:39 PM / IP Logged

It's not as simple as "keeping the same volume." Get the enclosure volume and tuning frequency and begin with the specs provided by JL. Then you can use a calculator and vary the one parameter you need to (such as length) to find out what diameter will give you the same tuning in your enclosure.

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kilj00y

Member - Posts: 25

Joined: October 19, 2004

Location: United States

Posted: October 21, 2004 at 3:12 PM / IP Logged

here is what is confusing me... if i input the jl specs of a port just to check (1 cu ft, 1 slotted port, 32Hz, and a slot 8.5 x 1.5) it tells me there should be NO LENGTH.

kilj00y

Member - Posts: 25

Joined: October 19, 2004

Location: United States

Posted: October 21, 2004 at 3:13 PM / IP Logged

never mind, wasnt checking slot port. thanks for all the help guys, i LOVE this forum!

killerfishes

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Joined: September 08, 2004

Location: United States

Posted: October 21, 2004 at 4:09 PM / IP Logged

good luck to you.

I just hit 133 DB with mine in a regular cab Dakota using the recomended size.

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8w7 port length

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