FE126E enclosure question

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I think more of a simple math question but I can't seem to get it straight. I am working on the recommended FE126E enclosure which is a hybrid back loaded horn / bass reflex design. Anyway I want to convert the port to english units from millimeters (don't have an 30 mm pipe!)

I know the port is 30mm diameter and 115 mm in length and Fb is 55 Hz

Due to the design I don't know what to include to calculate the enclosure volume.

What would the length need to be to use 1.5" port?

Thanks in advance,
Tim

Here is a link to the design:
http://www.madisound.com/pdf/fostexcabs/fe126e_encl.pdf

😕
 
Thanks for the reply and I will keep an eye on that thread to see what others are trying out.

I don't have any issue converting the mm to inches but the port comes out to 1.18" in diameter and 4.5" long. I don't have any material that is that diameter and wondered how to calculate the new length if I change the diameter to 1.5"..

Maybe I'm not making sense...
(wouldn't be the first time)

Tim
 
Greets!

Ron E's take on scaling vents:

.........L1/L2 = A1/A2, where L1, A1 are the original length and area, and L2,A2 are the new length and area... rearranging again, and Realizing that area is proportional to diameter squared:

L2 = L1*(D2^2/D1^2), where D2 is new diameter and D1 is the original diameter.

FWIW, *in sims* using MJK's WSs I found that accounting for the end correction difference was more accurate, probably audibly so if a big change in diameter was made, but as always YMMV:

L2 = L1*(D2^2/D1^2)+(D2-D1)^2

GM
 
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