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port length and tuning?

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=134755
Printed Date: May 11, 2025 at 4:25 PM


Topic: port length and tuning?

Posted By: ncc74656
Subject: port length and tuning?
Date Posted: August 18, 2013 at 2:03 PM

I have been using torres tuning calculator to find port lengths for tuning. i now see this program may be incorrect but in my search for answers i can not find any 2 programs that give the same results.

how do i know if a program wants me to input net or gross volume? if the program wants the cubic footage before or after port displacement? if its taking into account end correction or if i need to factor that in myself?

the calculator on here is 16 inches different from the calculator on wwww.mobileinformationlabs.com wich is also 5" different from torres wich is 6.25 inches different from winisd...

this is math, plane and simple! i should not find that every God D*** calculator gives me different result. i have no idea if my current box is 34hz, 28hz or 46hz with the margin of error on these programs.


I am wanting to build a 4th order but i cant even get a basic port tune correct here.   i want to know 100% how to verify that my port is indeed getting the tuning i think it is.

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ZX2500.1 - SP4 18"
Eclipse 34320 - dual 10" mids
Audiobahn A275HC - tweets
KX3 xover
P7800HD deck
knukonceptz wire
custom 3/8" copper plate ANL fuse
4 group 31 1150CCA batteries



Replies:

Posted By: DYohn
Date Posted: August 18, 2013 at 5:49 PM
You could always calculate it yourself.

Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)

where,

    Dv = port diameter (cm)
    Fb = tuning frequency (Hz)
    Vb = net volume (litres)
    Lv = length of each port (cm)
    Np = number of ports
     k = end correction (normally 0.732)

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Posted By: ncc74656
Date Posted: August 18, 2013 at 10:53 PM
49.816117" is what i get

here are my numbers, does this look right?

1.463*10^7*(11.941)^2/(45^2*15310.08)]-1.463*11.941

-------------
ZX2500.1 - SP4 18"
Eclipse 34320 - dual 10" mids
Audiobahn A275HC - tweets
KX3 xover
P7800HD deck
knukonceptz wire
custom 3/8" copper plate ANL fuse
4 group 31 1150CCA batteries




Posted By: ncc74656
Date Posted: August 22, 2013 at 7:57 PM
maybe?

-------------
ZX2500.1 - SP4 18"
Eclipse 34320 - dual 10" mids
Audiobahn A275HC - tweets
KX3 xover
P7800HD deck
knukonceptz wire
custom 3/8" copper plate ANL fuse
4 group 31 1150CCA batteries




Posted By: DYohn
Date Posted: August 23, 2013 at 3:11 PM
The formula requires metric input and returns a length in centimeters. That's why I posted the meaning of each term with the units required. So, if you input the other parameters in the proper units, the result will be in centimeters, not inches.

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