Port length math problem...

[coolest user 10+ year member]

I was looking at the PDF file for JL Audio 12W1's and I can't seem to figure out the math on the port. The port is supposed to be 33.75" long, and it has the "port extension length" listed as 14.5". The box is 17" deep.

How did they come up with 14.5" for the "port extension length" ? My math tells me the "port extension length" should be longer than 14.5" though. I'm still learning, so maybe someone could explain to me how JL got their number...

Here is a link to the file with the box size

http://mobile.jlaudio.com/pdfs/8429.pdf

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Click to read more...

 

[Brian Owens 10+ year member]

17 + 14.5 = 31.5 Then add 1/2 of the width, 31.5 + .75 = 32.35

They are off a little. Maybe it is a mistake, maybe they tested the design. . .They say 33.75" would be a 28 Hz tuning, and that does not calculate out correctly either.

I would build it as shown. It calculates out as just shy of 2 ft tuned to 30 Hz.

 

[PSturmer 10+ year member]

i checked into jl before. they said it was supposed to be a certain tuning and i looked at there plans and checked the math and got something completly different.