8w7 port length
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=41340
Printed Date: May 28, 2024 at 9:44 PM
Topic: 8w7 port length
Posted By: kilj00y
Subject: 8w7 port length
Date Posted: October 20, 2004 at 11:17 PM
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".
Replies:
Posted By: boxmaker85
Date Posted: October 20, 2004 at 11:23 PM
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.
Posted By: kilj00y
Date Posted: October 20, 2004 at 11:34 PM
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
Posted By: stevdart
Date Posted: October 21, 2004 at 8:56 AM
https://www.carstereo.com/help2/Articles.cfm?id=31 is one of the tools found here: https://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.
Posted By: kilj00y
Date Posted: October 21, 2004 at 12:40 PM
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.
Posted By: DYohn
Date Posted: October 21, 2004 at 2:39 PM
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. ------------- Support the12volt.com
Posted By: kilj00y
Date Posted: October 21, 2004 at 3:12 PM
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.
Posted By: kilj00y
Date Posted: October 21, 2004 at 3:13 PM
never mind, wasnt checking slot port. thanks for all the help guys, i LOVE this forum!
Posted By: killerfishes
Date Posted: October 21, 2004 at 4:09 PM
good luck to you. I just hit 133 DB with mine in a regular cab Dakota using the recomended size.
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