PDA

View Full Version : Port Area Question



1990RANGER
06-30-2005, 06:26 PM
Is it bad to have a port area thats larger than the calculated "minimum usable vent area"?

Cause on the box I'm designing, I need a minimum vent area of 21.69 inch^2, but is there like a maximum measurment you shouldnt pass?

cjjackson85
06-30-2005, 06:27 PM
Yes.

g30ffr3y
06-30-2005, 06:28 PM
Is it bad to have a port size thats larger than the calculated "minimum usable vent area"?

Cause on the box I'm designing, I need a minimum vent area of 21.69 inch^2, but is there like a maximum measurment you shouldnt pass?


there is a ratio that someone will post who is smarter than me...

cjjackson85
06-30-2005, 06:28 PM
there is a ratio that someone will post who is smarter than me...
Anyone feel free to speak up then...

Nikuk
06-30-2005, 06:30 PM
For a given tuning goal: You have to realize that the larger Your port mouth is, the longer the port will be, therefore taking up more volume, therefore raising tuning.

Nikuk
06-30-2005, 06:30 PM
Fs=0.159*(((Av*(1.84*10^8))/((Vb*1728)*(Lv + 0.823*(Av^0.5))))^0.5)

1990RANGER
06-30-2005, 06:32 PM
Yes.

Alright. Well then lets assume the box has a min. port area of 21.69 inch^2. Would i be bad if the port didn't go all the way across the the chamber?

Nikuk
06-30-2005, 06:33 PM
Alright. Well then lets assume the box has a min. port area of 21.69 inch^2. Would i be bad if the port didn't go all the way across the the chamber?

MS Excel is Your friend...


Fs=0.159*(((Av*(1.84*10^8))/((Vb*1728)*(Lv + 0.823*(Av^0.5))))^0.5)

1990RANGER
06-30-2005, 06:39 PM
MS Excel is Your friend...

Yea, LOL

cjjackson85
06-30-2005, 06:39 PM
:rotflol:

1990RANGER
06-30-2005, 06:40 PM
But I still need to know, would it be bad if the port mouth didn't go all the way across the chamber but the port wall did?

Nikuk
06-30-2005, 06:41 PM
http://img.photobucket.com/albums/v492/NjccBflo/lahlah.gif

Nikuk
06-30-2005, 06:41 PM
But I still need to know, would it be bad if the port mouth didn't go all the way across the chamber but the port wall did?

no. i've done it a few time before.

snebes
06-30-2005, 06:43 PM
It may look fugly, but if you mean what i think you mean, it will be cool. just center the port so it doesn't look fugly

edit:

I am thinking that on the inside, you wall off the unused area on the side of the port, which is equal size from the mouth to the azz, not the width of the box.

if this is not true, listen to nick

1990RANGER
06-30-2005, 07:05 PM
Okay. I really dont mean to beat this topic to death since u guys already answered my question, but I just want to make sure I'm on the same page as u guys cause it seems like I may be almost done with my design :veryhapp: .

In the pic below the red hatched area is the the exposed port mouth and the yellow hatched area is the intrenal port space created by the back wall and port wall.

http://gallery.caraudio.com/vg/2/0/7/0/4/dfgdf.bmp

So still, there is nothing wrong with this design?

d cha p
06-30-2005, 07:48 PM
that pic makes it look like the port mouth is smaller than the port chamber. If that is the case then those designs are for a sealed box with a big hole in it.

1990RANGER
06-30-2005, 08:11 PM
Well, the port mouth is smaller than the the port chamber. The width will always be kept at the 2 inches but the length of the port mouth will be 11 inches and the lenght of the port in the box will be stretched out to 20.5 inches (which is the length of the boxs chamber.

So then, there will be a 20.5 inch x 14.69 inch port wall along with a 2nd port wall which isnt shown in the pic.

I mean...., theres going to be port walls in chambers and eveything, so what am I not understanding?

Nikuk
06-30-2005, 08:31 PM
why not just keep the port the same size the throughout the length of it?? It's much better that way...

You CAN do it the way that You've illustrated, but it's not the best idea.

-Nick

1990RANGER
06-30-2005, 08:50 PM
why not just keep the port the same size the throughout the length of it?? It's much better that way...

You CAN do it the way that You've illustrated, but it's not the best idea.

-Nick

So should I basically seal that part of the box off? And wouldn't that mean that I'd have to seal that 3" throught out both sides of the chamber? I'd lose a lot of volume like that. Or would I not have to extend the seal past the first port wall?

1990RANGER
07-03-2005, 03:41 PM
I got some more questions *sigh*.

1. when calculating total internal volume for a sub, do you subracted the volume created by the ports?

2. do you need a 2nd port wall after the second one? Cause I was reading kicker's tech tips and they never metioned anything about it and didn't have pics of boxes with a 2nd wall.

Thanks

d cha p
07-03-2005, 05:40 PM
your questions donít make much sense :eyebrow: .

Based on the description of your box, I think your port should look something like this...
http://img80.imageshack.us/img80/261/20050324oooiopi00890ys.th.jpg (http://img80.imageshack.us/my.php?image=20050324oooiopi00890ys.jpg)
Now take the length of the port and multiply it by the highth of the port + .75 and the width of the port + .75. The extra .75 is too account for the width of the wood you will use. This will give you the total volume of your port. Now account for the port volume by subtracting it from the box volume too determine your net volume.