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View Full Version : Yet another Help Thread for a ported Box



spydyplayer
06-04-2005, 12:22 AM
Okay...I just got done doing the huge port formula and came up with an off the wall number so here goes my situation.....I'm building a ported box....The external dimensions would be 38" by 38" by 15". This would make the internal dimensions 36.5" by 36.5" by 13.5". I want the box to have an airspace of 6 ft^3 @ 35 hz. I was thinking I would make my port 35" by 4"...or a port area of 140 in^2...When I plug all of this into the formula...I come up with a port length of 4.334 in long....That doesn't seem right to me...Maybe it is because my port area is so huge...I'm not totally sure...I'm completely new to the ported box building as all I've ever built have been sealed. Can somebody point me in the right direction? I have a feeling that my fault lies in the chosen size of my port but who knows...Also... in the thread about building a ported box with George or whatever....which I am using to guide me through my box building adventure...He refers to the second wall...This is where I got lost...can somebody help me...I'm goin nuts...Maybe a drawn diagram of his idea might help.........Thanks in advance to whomever should attempt to help me.

1990RANGER
06-04-2005, 02:21 AM
I'm kinda new to this stuff and also in your situation. I was also thrown off by the 2nd wall thing until I looked at a pic of a ported box. Here's a pic I drew for one of my threads......
http://gallery.caraudio.com/vg/2/0/7/0/4/portedbox.bmp

Notice the 2nd board from the left side, I believe thats the second wall George is talking about in his post.

dopey
06-04-2005, 06:49 PM
The problem is the size of your enclosure. General rule of thumb for ported enclosures.
To keep the same tuning frequency:
-If you increase box volume , you decrease port length
-If you decrease box volume, you increase port length
-if you increase port diameter , you increase port length
-if you decrease port diameter, you decrease port length
-to raise tuning freq, shorten length
-to lower tuning freq, lengthen the length.

Hope this helps..