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calculator for port size and length of box or tube


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crroush 
Copper - Posts: 151
Copper spacespace
Joined: August 02, 2002
Location: United States
Posted: November 20, 2002 at 10:40 PM / IP Logged  

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

the12volt 
Administrator - Posts: 3,956
Administrator spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spaceThis member has been recognized as an authority in Mobile Security and Convenience. Click here for more info.spacespace
Joined: March 07, 2002
Location: Louisiana, United States
Posted: December 26, 2002 at 11:09 AM / IP Logged  
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 
Sound Pressure 
Silver - Posts: 711
Silver spacespace
Joined: March 09, 2002
Location: United States
Posted: December 27, 2002 at 2:38 AM / IP Logged  
Thankyou 12volt, and crroush.
Sound Pressure
You know you have the right amount of pressure when your eyes start to water! Now you've got Juice!
Sound Pressure 
Silver - Posts: 711
Silver spacespace
Joined: March 09, 2002
Location: United States
Posted: December 27, 2002 at 2:40 AM / IP Logged  

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!
the12volt 
Administrator - Posts: 3,956
Administrator spaceThis member has made a donation to the12volt.com. Click here for more info.spaceThis member has been recognized as an authority in Electrical Theory. Click here for more info.spaceThis member has been recognized as an authority in Mobile Audio and Video. Click here for more info.spaceThis member has been recognized as an authority in Mobile Security and Convenience. Click here for more info.spacespace
Joined: March 07, 2002
Location: Louisiana, United States
Posted: December 27, 2002 at 7:55 AM / IP Logged  
You're welcome and Thanks :)
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