calculator for port size and length of box or tube
Printed From: the12volt.com
Forum Name: New Ideas for the12volt.com
Forum Discription: Tells us what you'd like to see on the12volt.com.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=5019
Printed Date: May 02, 2025 at 4:16 AM
Topic: calculator for port size and length of box or tube
Posted By: SOUND PRESSURE
Subject: calculator for port size and length of box or tube
Date Posted: November 01, 2002 at 1:36 AM
Hey 12volt, Wondering if there is someway to add a calculator to find the correct size and length of a port for a box or tube given the measurements? Might be another helpful tool. ------------- Sound Pressure
You know you have the right amount of pressure when your eyes start to water! Now you've got Juice!
Replies:
Posted By: the12volt
Date Posted: November 02, 2002 at 12:17 PM
Hi Sound Pressure, great idea! I use a port tuning nomogram to determine port sizes based on desired port frequency and the volume of the enclosure. I'll scan one and upload it for you. If I can find a mathamatical formula, I can write a calculator for everyone to use. I'll keep you posted. the12volt
Posted By: SOUND PRESSURE
Date Posted: November 02, 2002 at 10:08 PM
Thanks 12volt I appreciate it.
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Sound Pressure
You know you have the right amount of pressure when your eyes start to water! Now you've got Juice!
Posted By: the12volt
Date Posted: November 04, 2002 at 5:21 PM
Here ya go Sound Pressure: Port Tuning Nomogram I believe I found an equation that will provide the same results. When I have time, I'll try it out and if successful, I'll write a calculator for everyone to use. the12volt
Posted By: SOUND PRESSURE
Date Posted: November 07, 2002 at 12:45 AM
 Thanks again 12volt,
So much time and headaches you have saved. I will download it once I get home today. ------------- Sound Pressure
You know you have the right amount of pressure when your eyes start to water! Now you've got Juice!
Posted By: the12volt
Date Posted: November 07, 2002 at 9:34 AM
Hi Sound Pressure, you're welcome, glad I could help ;)
Posted By: SOUND PRESSURE
Date Posted: November 17, 2002 at 7:25 PM
Hey 12volt, I have a little trouble opening the program. It won't open  I have saved it to a floppy but still can not open it. Please help. ------------- Sound Pressure
You know you have the right amount of pressure when your eyes start to water! Now you've got Juice!
Posted By: the12volt
Date Posted: November 17, 2002 at 8:05 PM
Sound Pressure, you need to unzip it with your favorite zip utility: WinRAR, WinZip, PKZip. The file contains a printable nomogram and instructions.
Posted By: SOUND PRESSURE
Date Posted: November 17, 2002 at 11:50 PM
Can you tell that I was really lost! Thanks 12volt, I will try that in the morning when I get home from work.
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Sound Pressure
You know you have the right amount of pressure when your eyes start to water! Now you've got Juice!
Posted By: the12volt
Date Posted: November 18, 2002 at 12:55 PM
Not a problem. Once you unzip it, print a copy of the namogram each time you want to use it, follow the instructions I included, and you should be set.
Posted By: crroush
Date Posted: November 20, 2002 at 10:40 PM
Here is the equation I use so you can make a calculator input = Radius of Port (R), tuning frequency in Hz (fb), Volume of the box in cubic inches (Vb) and the length can be computed by: L = (1.463 * 10^7 * R^2)/(fb^2 * Vb) - 1.463R Note this is an approximate equation that generally gets you in the ball park, but if you are using flanged ports and different geometries other than a standard "box" there are other optimization techniques that can be done. I do a bunch of my modeling using a variety of genetic algorhytims I wrote using the toolboxes in Matlab that seem to work pretty well, let me know if this will work, it is the standard equation from my favorite book "The Loud Speaker Design Cookbook, by Vance Dickason" :) Craig
Posted By: the12volt
Date Posted: December 26, 2002 at 11:09 AM
Hi Sound Pressure, after doing some research of my own I found the same formula Craig posted "L =((1.463 * 10^7 * R^2)/(fb^2 * Vb) - 1.463R)" and converted it to this "L = ((14630000*(D/2)*(D/2))/((Fb*Fb*Vb*1728)-(1463*(D/2))))" which is the same thing, just longer, and wrote this: https://www.the12volt.com/caraudio/boxcalcs.asp#por
Posted By: SOUND PRESSURE
Date Posted: December 27, 2002 at 2:38 AM
Thankyou 12volt, and crroush.
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Sound Pressure
You know you have the right amount of pressure when your eyes start to water! Now you've got Juice!
Posted By: SOUND PRESSURE
Date Posted: December 27, 2002 at 2:40 AM
Hey 12volt, Good idea with the series and the parallel calculator. I'm sure that should clear up alot of headaches for some. ------------- Sound Pressure
You know you have the right amount of pressure when your eyes start to water! Now you've got Juice!
Posted By: the12volt
Date Posted: December 27, 2002 at 7:55 AM
You're welcome and Thanks :)
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