Tweakers' Asylum

Port length sizing with tapered port...

98.180.214.67

Guys,

I could really use some helps with this.

I have ordered some "1-7/8" ports from Part Express for DIY speakers. The port length I calculated is 4.8". However, the port turn out to have different diameter on both ends. The diameter on the opening go inside the box is 1-5/8" and the opening face outside the box is 1-6/8".
I am at a loss as of how to re-calculate the length.

WinISD is what I used.

Thanks.

Follow Ups:

RE: Port length sizing with tapered port... - Paul J. 11:21:36 03/02/10 (0)
It will probably be a negligible difference when compared to driver specs variances, actual box volume (the effects of the driver's volume, stuffing, losses, etc) and especially in-room behavior. That being said, you might consider measuring the results, as others suggested. The easiest path might be to purchase the Parts Express Woofer Tester.

If you want to simulate the effects of the port's taper though, David McBean's Horn Response will do it. You can make the port any combinations of cross section vs. length you want. It is an excellent program, capable of much more interesting things than many other box calculators, and it is free! He recently moved to a different blog site, but I think I have a link to the most recent version (which is much more fun than previous versions). Even if you are no longer concerned about this problem, Horn Response is worth getting to know.

Paul
- http://www.dmcbean.bigblog.com.au/index.do (Open in New Window)
RE: Port length sizing with tapered port... - Ron Oehlert 12:50:54 02/24/10 (0)
Apply 1 & 11/16 as diameter (the average from front to back). Or, it does seem as if you were shipped the wrong part; what about a return/exchange for the correct part vs making do?

Edits: 02/25/10
RE: Port length sizing with tapered port... - djk 05:40:30 02/24/10 (0)
Measure the cone motion null and trim the port length to get target box Fb.

Marchandelec.com offers free software for the frequency generator.

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