Need Help With Port Dimensions

[jlgn_2000]

here is my build

http://www.stevemeadedesigns.com/board/ind...showtopic=20871

So I am in the process of building the box for my sub, i'm not going to wall it, the box is just going to be built into the back seat. I'm going over the manual and it says the box should be 5 cubes plus half a cube for the port. The inside dimensions are going to be 15"x16"x36" and the inside dimensions of the port is going to be 15"x3"x16" ( the manual said to add an extra 1.5" to the length of the port since it will have 90 degree angle which will tune it to 35 Hz.

My question is this, I want to have my sub and port centered, like this:

The pic would be looking down at the box with the sub being closer to the front of the car and the port closer to the back.

(yes, I suck at paint). In the manuals the port is always at the opposite side of the sub, do you guys think this will be ok?

The car is a 3000gt so it is a hatchback and the sub is being powered by a kx2500.1

*fixed the pic

Edited August 7, 2008 by jlgn_2000

[jlgn_2000]

this is a better pic

the front of the box is going to be cut later at an angle so i can lean the seat back

[jlgn_2000]

Someone has to have tried this before...any input would be helpful

[jlgn_2000]

What if I was to do 2 ports instead of one. The manual says to do 60 sq inches of port at 14.5 inches long. What if I was to do two smaller ports, each 30 sq inches and each 14.5 in long? would the tuning still be the same?

I would have the ports like this, where the green is

Edited August 6, 2008 by jlgn_2000

[V1G1LANT3]

What if I was to do 2 ports instead of one. The manual says to do 60 sq inches of port at 14.5 inches long. What if I was to do two smaller ports, each 30 sq inches and each 14.5 in long? would the tuning still be the same?

I would have the ports like this, where the green is

no that would be different tuning. I have been debating which way to face my port too..so im interested in the replies

[Frozenbritches]

Not that I'm an expert or anything but, I think where ever the port is doesn't matter as long as it is tuned correctly.....it's just how air escapes...now if you had it like, right under the sub there would probably be a problem lol..

GL with it...and GL with weight lifting lol...

[V1G1LANT3]

I just noticed you are using a kicker sub...similar to my build. Im using one L7 15" though with two ports, but I am only using two to make it symmetrical.

Use this to figure up port length if you are doing two. Only difference to get tuning with more than one port is to take your expected airspace and divide it by the number of ports. So if you are going for a 5 ft^3 box, you would put 2.5 ft^3 in this formula instead.

Lv = port length

Av = your port area (height x width of the port face)

Vb = the internal volume of your box

Fb = the tuning frequency you want

You could also use the calculator on carstereo.com but this is more accurate.

[jlgn_2000]

I just noticed you are using a kicker sub...similar to my build. Im using one L7 15" though with two ports, but I am only using two to make it symmetrical.

Use this to figure up port length if you are doing two. Only difference to get tuning with more than one port is to take your expected airspace and divide it by the number of ports. So if you are going for a 5 ft^3 box, you would put 2.5 ft^3 in this formula instead.

Lv = port length

Av = your port area (height x width of the port face)

Vb = the internal volume of your box

Fb = the tuning frequency you want

You could also use the calculator on carstereo.com but this is more accurate.

Thank you very much for the feedback. I am using two ports too because I want it symmetrical as well. Since the sub has to go in the middle I want to have a port on each side. So I took the formula and this is what I got:

I used:

Av=10 inch x 3

Vb=5 cubes (I input 2.5 into the formula)

Fb=35 Hz (I only used this because that is was the manual has the boxes tuned to, should I use something different?)

21.86=((10*3)*1.84*10^8)/(2.5*1728*(35/0.159)^2)-0.823*SQRT(10*3)

So to make sure I understand correctly I would use two ports, each with an internal dimension of 10x3 and 22 inches long and that should give me 35 Hz?

For some reason is seams really long. But this is my first time building a ported box so I am deffinately a noob in this area. Can someone confirm this for me?

[V1G1LANT3]

Sounds right...each will be 21.86.

http://www.carstereo.com/help/Articles.cfm?id=31 you should get something very close.

My ports came out huge at 21" long also..I have a smaller box too. What Im doing is making my ports removable..so I can build my box first then sort out the port length after and pop them in...after I know exact air space.

[jlgn_2000]

Sounds right...each will be 21.86.

http://www.carstereo.com/help/Articles.cfm?id=31 you should get something very close.

My ports came out huge at 21" long also..I have a smaller box too. What Im doing is making my ports removable..so I can build my box first then sort out the port length after and pop them in...after I know exact air space.

Thats a good idea but I wouldn't really be able to do that with my box because of the small amount of space I have to work with the port has to have a 90 degree angle in it.

So what I am gonna do is have two ports, one on each side of the box each with an internal dimesion of 10x3x22. Now my only problem is I have to make sure that the total volume of the box is 6.3 cubes since the two ports would take up 1.3 cubes.

....Well no one ever said car audio was easy...but I'm sure i'll be able to knock it out :aggressive: Thanks for all the help, I'll have more progress by sunday night hopefully