End correction question

[Beginer 10+ year member]

Hello,

I've been searching and found some threads about end correction, but still I don't get it //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

I use this formula to findout box tuning freq.:

Fb = 0.159*SQRT[(Av*(1.84*10^8)]/(Vb*1728*[Lv+(.823*SQRT(Av))])

Vb - net volume(all displacements taken into account), Fb - tuning freq., Av - port area, Lv - length of the port.

1. Does this formula include end correction?

2. Let's say I want to build 2.5cu.ft., port 4" width, 13" height, tuned to 45Hz. So what physical length of the port should be?

I get ~20". So physical port length should be 18" (20"- 2"(half port width))? //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

Thanks.

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[FI15INCH 10+ year member]

I understood everything up to Fb =

 

[Immacomputer 10+ year member]

So physical port length should be 18" (20"- 2"(half port width))? //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif
Thanks.

That's correct when one of the port walls is also an enclosure wall.