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-   -   different port diameters in a single subwoofer box? (http://www.diyaudio.com/forums/subwoofers/197204-different-port-diameters-single-subwoofer-box.html)

ThyDntWntMusic 24th September 2011 09:53 AM

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?

geraldfryjr 24th September 2011 11:44 PM

Yes,You use the total area of the two tubes to the determine the length and both tubes shall be the same length.

jer :)

ThyDntWntMusic 25th September 2011 12:56 AM

have you done this before?

revboden 25th September 2011 12:57 AM

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.

ThyDntWntMusic 25th September 2011 01:01 AM

I'm going to guess that no one has actually tried this :p

geraldfryjr 25th September 2011 01:08 AM

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 :)

revboden 25th September 2011 01:11 AM

I've tried it. it dosen't work. The ports couple to the internal volume differently and it makes a slurry mess.

ThyDntWntMusic 25th September 2011 01:15 AM

Quote:

Originally Posted by revboden (Post 2722923)
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?

revboden 25th September 2011 01:20 AM

Quote:

Originally Posted by geraldfryjr (Post 2722920)
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

revboden 25th September 2011 01:29 AM

Quote:

Originally Posted by ThyDntWntMusic (Post 2722927)
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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