How do i know what my port area should be?

[dsw422]

i use winisd but it doesn't tell you which port area would be most efficient

it does.. when you have a box designed.. you need to enter how much power the speakers will be getting.. then you go to rear port air velocity graph.. youll need to adjust port area till you get 20m/s or under..

heres the graph i am talking about..

http://www.hometheatershack.com/gallery/images/9992/1_WinISD-15.gif

[Triticum Agricolam]

i use winisd but it doesn't tell you which port area would be most efficient

32 m/sec is what I consider to be the hard cut off, I try to never go above that.

24 m/sec and below is what I shoot for with most car audio sub boxes.

17 m/sec and below is what I shoot for with home audio subs.

You can use WinISD to show you approximately what port velocity you are going to get. Keep in mind WinISD doesn't compensate for high aspect ratio ports, or port that need a lot of bends in them, or anything else that is going to negatively effect how easily air can flow through that port. These are things you have to factor in yourself.

[dsw422]

i use winisd but it doesn't tell you which port area would be most efficient

32 m/sec is what I consider to be the hard cut off, I try to never go above that.

24 m/sec and below is what I shoot for with most car audio sub boxes.

17 m/sec and below is what I shoot for with home audio subs.

You can use WinISD to show you approximately what port velocity you are going to get. Keep in mind WinISD doesn't compensate for high aspect ratio ports, or port that need a lot of bends in them, or anything else that is going to negatively effect how easily air can flow through that port. These are things you have to factor in yourself.

I knew you'd comment soon to help set him straight..

[reedal]

More port area = less port velocity, longer port for the same tuning as a smaller port. From all of the information I've gathered when trying to design my enclosure for the same subs, net volume should be between 4.5ft^3 and 5ft^3 on rated power. One build log on here, the guy said 5ft^3 it was too peaky for him, so he built it again at 4.5 net at the same tuning and liked it better, I don't know what power he was running off the top of my head. Tuning affects the frequency response as well. lower tuning offers a flatter response, higher tuning makes it more peaked around tuning. At least for my enclosure when modeled in winISD. When I get home tonight I'll get on my computer and share what I have saved with you.

[CamEnglish]

Will the port close to the back wall like this make it less efficient? http://i1148.photobucket.com/albums/o565/GlobalFriction/Caadfsdfpture.png

[CamEnglish]

i guess this is a better pic http://i1148.photobucket.com/albums/o565/GlobalFriction/Capturssssssssssssse.png

[Broke_Audio_Addict]

The port has to be farther away from the back wall than the port is tall or you choke the port.

[CamEnglish]

thanks i didnt think about that

[CamEnglish]

is this too peaky? This is my first box so i dont know if this would sound like shit or what http://i1148.photobucket.com/albums/o565/GlobalFriction/Captssssure.png

[reedal]

That's about all I can get from it too. nothing but a huge peak until tuned to around 20hz. A little too much for my taste. I think the design I came up with a while back has about 94in^2 of port area, and tuned to 33hz, 5.07ft^3. I just haven't been having luck trying to even it out.