different port diameters in a single subwoofer box? - diyAudio
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Old 24th September 2011, 09:53 AM   #1
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Default different port diameters in a single subwoofer box?

can this work?

lets say you had a 4inch diameter port, and a 6inch, in the same enclosure, both the same length.

would you simply take the total port area when determining the required length?
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Old 24th September 2011, 11:44 PM   #2
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Yes,You use the total area of the two tubes to the determine the length and both tubes shall be the same length.

jer
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Old 25th September 2011, 12:56 AM   #3
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have you done this before?
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Old 25th September 2011, 12:57 AM   #4
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not quite, if both tubes are the same length the smaller one would be tuned lower than the larger one. basically it's a bad idea as the larger port would blow out before the smaller one, you'd be making a leaky BR box.

Also when tuning for multiple ports you have to divide the Vb by the number of ports then do the calculation for each. That's why port length gets longer the more ports you add.
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Old 25th September 2011, 01:01 AM   #5
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I'm going to guess that no one has actually tried this
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Old 25th September 2011, 01:08 AM   #6
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No,I haven't done this before it was just a therotical calculation I would use tubes of the same size Myself.
But I don't see why it wouldn't work as the work of the port is its total area with its length. Even when using mutiple ports in Winlsd it still works out as one port the the same area as the total area of two or more ports.

Maybe some one whom has tried this can elaborate more on the subject.
I don't have a box readily availible to test this theory at the moment.

jer

Last edited by geraldfryjr; 25th September 2011 at 01:11 AM.
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Old 25th September 2011, 01:11 AM   #7
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I've tried it. it dosen't work. The ports couple to the internal volume differently and it makes a slurry mess.
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Old 25th September 2011, 01:15 AM   #8
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Quote:
Originally Posted by revboden View Post
I've tried it. it dosen't work. The ports couple to the internal volume differently and it makes a slurry mess.
what exactly did you try?
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Old 25th September 2011, 01:20 AM   #9
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Quote:
Originally Posted by geraldfryjr View Post
No,I haven't done this before it was just a therotical calculation I would use tubes of the same size Myself.
But I don't see why it wouldn't work as the work of the port is its total area with its length. Even when using mutiple ports in Winlsd it still works out as one port the the same area as the total area of two or more ports.

Maybe some one whom has tried this can elaborate more on the subject.
I don't have a box readily availible to test this theory at the moment.

jer

plug this into winisd
open two project boxes with the same driver ported 2.5ft^3
first project with one port 5" diameter 18.84"
second with two ports 3.535" diameter
they have the same cross area but the box with two ports will be longer by an inch
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Old 25th September 2011, 01:29 AM   #10
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Quote:
Originally Posted by ThyDntWntMusic View Post
what exactly did you try?
this was years ago,
I wanted to get a dual tuned box one port tuned to 14Hz the other larger tuned to 18Hz. I thought i'd use it to tune the box with a larger region of port output but the two ports worked against each other and there was almost no port output. This was before I understood the physics of resonators. knowing what i know now I would have just plugged one or the other to get a tunable box
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