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photocrazy8
03-15-2006, 10:27 PM
I have a JL Audio 12w3v2 D4 and im trying to make a ported box in WinISD beta. I put in 2.7 cubs and 43Hz. It says that the port should only be 5.61 in. Is that right? Sounds a little too short to me. Thanks, Andrew

j3bus2k3
03-15-2006, 10:35 PM
holy hell! 43hz?! I hope this is a competition box...otherwise tune lower bro. But I would wager a bet that you dont have enough port area, makin for some port noise.

photocrazy8
03-15-2006, 10:52 PM
ok, so i changed it to 35Hz at 2.5 cubes. the post with is 4 in wide and the port length is 11 in...does this sound about right? thanks andrew.

im using WINISD beta.

matt_martin87
03-15-2006, 11:06 PM
The length should be right around 8 and 1/8 inches. I used the pen and paper method so I'm almost 95% sure this is correct. Someone please correct me if I'm wrong.

photocrazy8
03-15-2006, 11:12 PM
thanks, im excited to start building. should i just use one of the side of the box as part of my port and put in another piece of MDF or the other side (4 in wide)? thanks

matt_martin87
03-15-2006, 11:15 PM
Yes. Just have a look at Moe's plans for a general idea of what it would look like.

http://img10.imageshack.us/my.php?image=09cubes35hz21sqin9ui.png

photocrazy8
03-15-2006, 11:18 PM
sweet, thanks

photocrazy8
03-15-2006, 11:22 PM
I just thought of this. if the ports are 4in wide, how tall should they be then? cause there are tons of diff dimentions to get to 2.5cubs? thanks

matt_martin87
03-15-2006, 11:27 PM
I just realized that this is a slot ported box you want to build. I'll need to know how much port area you want before I can go any further.

Sorry.

photocrazy8
03-15-2006, 11:30 PM
slot port, the dementions that WINISD says is 18 x 28 x 11.5. if its not too hard could you tell me how to figure it out so i dont have to keep asking people every time i want to make a box. thanks

photocrazy8
03-15-2006, 11:38 PM
well i thought the side of the port determins the tuning Hz. and i was going to tune it to 35Hz in 2.5cubs. thanks

matt_martin87
03-15-2006, 11:40 PM
All I need to know now is how tall your box is.

To tell you the truth, its not really easy for me to explain it. Just keep reading and gaining knowledge, but in the meantime, you'll just have to ask.

photocrazy8
03-15-2006, 11:46 PM
it does not matter so i guess we can go 18in tall x 28 wide and 11.5 deep like WINISD said would be best. but you know more than me so you can change the height etc. is there some place where you learned? thanks

matt_martin87
03-15-2006, 11:56 PM
In order for me to give you a vauge idea of what your box will look like, I'll need to know the following:

-What JL recommends for port area on that particular sub: ?
-Net volume: 2.5cuft
-Max gross volume(the biggest volume you can work with, and please specify what dimensions are what): ?
-Tuning freq.: 35hz

I learned all this on the forums just by reading every bit of information I could on building boxes. Its hard to catch on a first, but hang in there.

photocrazy8
03-16-2006, 12:06 AM
JL says 30.3 Hz

and i dont have a space limit


sorry if its not right, im getting a little confused

PowerNaudio
03-16-2006, 06:30 AM
just a note on winISD and ports:
and the reason that some software differ from other software and paper calculations on port length.


WinISD calculates port length assuming that there are one flanged and one free end, i.e. port is mounted to the wall of the box, and another end is freely inside the box. So end correction factor is 0.732 by default. Port length in box wall is counted to port length. If you want do convert the result to different end correction, then add 0.732 times diameter of the port to calculated port length. This gives you needed acoustical length of port. Then add end correction as you like

End correction
End correction factor is analytically or empirically determined factor, how much port extends beyond its physical ends. For free end, end correction is 0.30665 times port effective diameter. For flanged end, more analytical expression is available, 4/(3Ěpi) ~= 0.42441 times port effective diameter. Flanged end is calculated assuming that tube terminates to infinite baffle. Which is not exactly true, but.. Following table summarizes various port configuration types and their total end correction factors (refer to above picture to various end types):

Summary of end correction values Port configuration end correction 1 end correction 2 Total end correction
Two free ends 0.30665 0.30665 0.6133
One flanged and one free end 0.42441 0.30665 0.7311
Two flanged ends 0.42441 0.42441 0.8488

Physical port length is obtained by subtracting port effective diameter multiplied by suitable end correction value from port's acoustical length.

nVRuckus
03-16-2006, 08:33 AM
ok, so i changed it to 35Hz at 2.5 cubes. the post with is 4 in wide and the port length is 11 in...does this sound about right? thanks andrew.

im using WINISD beta.
depends on the size of the port opening itself. Also keep in mind winisd doesnt calculate the port's volume into the box when figuring it out so you need to figure that out and change the boxes size to remove that port volume.