Trying to understand a particular box design

[Goldtaz1 10+ year member]

Guys, I need some help with a box design I am looking at. See the attachment below because I made a drawing of what I am going for. When you see the picture, please assume that the port height is the same as the internal height of the enclosure. Here are my questions:

1) Would this design be considered as having two ports? If the enclosure has two ports then I assume I would be correct by doing the port length formula for two ports?

2) Would the woofers see both chambers for airspace since I am not putting in a divider?

3) If the width of the mouth opening is say 3 inches, do I stay off of the back wall 3 inches with both bends or do I stay from the backwall 1.5 inches?

Click to read more...

 

[req 5,000+ posts]

put a divider down the middle and make it wider so that the middle section is double the *internal* width of the bottom 'shafts' i suppose. each sub would be in its own seperate box. but you can NOT do a port like that where they both have two tails that share the same middle shaft.

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see the divider? then put the back two beside them or whatever. but you cant share the same middle one off to the others

 

[jellyfish420 10+ year member]

i would disagree with req.

you can do it the way you said. if you wanted the mouth to be 3" then you would figre the port for 1/2 the box. using 1.5" port. pretend that its 2 seperate boxes w/ 2 1.5" ports 'joined' together. i just did a box like this not to long ago

(internal pics)

http://forums.caraudio.com/vb/showthread.php?t=76593

(finished pics)

http://forums.caraudio.com/vb/showthread.php?t=78936

 

[Goldtaz1 10+ year member]

Thanks a bunch jellyfish, that definitely sheds light on my project. However, I just want to make sure I understand you correctly, here goes. If I am looking for 2 cubes PER woofer and say 42 square inches of port where the mouth is 3 inches wide and a tuning of let's say 33 Hz then in order to find port length I would perform my calculation using 1) 2 cubes net 2) 21 square inches of port and 3) the 33 Hz tuning frequency??? If this is correct then I knew I was making it more difficult then it really is?

Also, on your second link the pictures would not pull up, so would you mind sending those via PM or to Goldtaz1@charter.net?

 

[Insomniac119 10+ year member]

Also, on your second link the pictures would not pull up, so would you mind sending those via PM or to Goldtaz1@charter.net?

they worked for me.

 

[Goldtaz1 10+ year member]

they worked for me.

Still can't get em to work.

 

[BoomCrew 10+ year member]

worked for me at 6.03 on april 7th.

 

[jellyfish420 10+ year member]

Thanks a bunch jellyfish, that definitely sheds light on my project. However, I just want to make sure I understand you correctly, here goes. If I am looking for 2 cubes PER woofer and say 42 square inches of port where the mouth is 3 inches wide and a tuning of let's say 33 Hz then in order to find port length I would perform my calculation using 1) 2 cubes net 2) 21 square inches of port and 3) the 33 Hz tuning frequency??? If this is correct then I knew I was making it more difficult then it really is?
Also, on your second link the pictures would not pull up, so would you mind sending those via PM or to Goldtaz1@charter.net?

yes you are correct sir.

the pics don't work? huh, but the first ones do? they're both on the same server...

i'll see if i can find them.

for instance if you calculation comes to 30" long port and your box is 17" deep, you would take 3" down the middle, then you split it, and have 1.5" running each way 12.25"...make sence?

 

[jellyfish420 10+ year member]

Can anyone say, "Cancellation" ???

you were the one that helped me figure mine out when i did it, and there was no mention of cancelation...//content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

 

[Goldtaz1 10+ year member]

Can anyone say, "Cancellation" ???

This box design is still about as clear as mud to me. Jmac please clarify this issue, I don't think that either Jellyfish nor myself wants to build a completely worthless box?? Additionally, we don't want to go around advising other folks incorrectly, so please help us out on this one.

Jellyfish, I am quite positive that we are on the same sheet of music and I just wanted to let you know I appreciate your help.

 

[Goldtaz1 10+ year member]

Need some response on this.

 

[jellyfish420 10+ year member]

Need some response on this.

me too. i would like to hear about this.

i have already built my box. it sounded great! louder than the 'regular' ported that i just built for the 2-10's

 

[Goldtaz1 10+ year member]

me too. i would like to hear about this.
i have already built my box. it sounded great! louder than the 'regular' ported that i just built for the 2-10's

Do you know Jmac? Do you suppose we could go to him directly for some assistance? Anyone else familiar with this design please feel free to chime in.

 

[bcarpenterfhl 10+ year member]

yea. i thought there could be some cancellation issues, but was never vertain. so fo the boxes i design i give them two seperate ports just incase. (like the one in my sig).

 

[Goldtaz1 10+ year member]

Anyone see a problem here ?

The waves will be completely out-of-phase when the meet up in the center of the port and cancellation will occur ...

You should have a divider in the middle of the port ...

But I have seen many boxes built this way and they absolutely slammed. I am talking about boxes that were built by the professionals at my local car audio shop. One guy in particular has won numerous national awards for his builds. If you require his name then I can certainly provide that.

I guess the main reason I am questioning you on this is because Jellyfish stated that you helped him design his enclosure.