Can someone explain how to find the square inch per cubic feet when designing port?

[osiris10012]

How do you calculate the tuning from the net volume? Just curious because I know that the net includes the displacement of the port and the sub so I am a bit confused.

[osiris10012]

Ok JoeX I redid the port by measuring centerline to centerline and getting it to the 25.75". Does this look better? I got the port dimension by using the12volt's slot calculator with 1.38 cu.(gross) for the volume. Not sure how to tune it to the net, but I think I am getting closer to what I need. Do I factor the sub displacement in and then calculate the port length?

[Triticum Agricolam]

Ok JoeX I redid the port by measuring centerline to centerline and getting it to the 25.75". Does this look better? I got the port dimension by using the12volt's slot calculator with 1.38 cu.(gross) for the volume. Not sure how to tune it to the net, but I think I am getting closer to what I need. Do I factor the sub displacement in and then calculate the port length?

You need to factor in the sub displacement and the port's displacement. Basically the net volume of your enclosure is the free air space you have left. Figure out what you have for net volume on your design now and use that number to calculate the port length again. Its going to have to be longer since your net volume is going to be less than 1.38.

Its tricky in your case because you need to remove the amount of volume the port takes up, but you don't know what that will be until you calculate the length of the port.

[775Tundra]

Programs such as http://www.carstereo.com/help/Articles.cfm?id=31 account for port displacement as you increase the length of port. The only thing you have to account for before hand is the sub displacement. No reason in trying to figure out net volume before calculating your port.

[Triticum Agricolam]

Programs such as http://www.carstereo.com/help/Articles.cfm?id=31 account for port displacement as you increase the length of port. The only thing you have to account for before hand is the sub displacement. No reason in trying to figure out net volume before calculating your port.

I like that online calculator, but I don't see how it accounts for port displacement in its calculations.

[775Tundra]

Programs such as http://www.carstereo.com/help/Articles.cfm?id=31 account for port displacement as you increase the length of port. The only thing you have to account for before hand is the sub displacement. No reason in trying to figure out net volume before calculating your port.

I like that online calculator, but I don't see how it accounts for port displacement in its calculations.

the program tells you the port length after you tell it the volume and desired tuning. There will be no way for you to know the net volume before the program advises a length.

[Triticum Agricolam]

the program tells you the port length after you tell it the volume and desired tuning. There will be no way for you to know the net volume before the program advises a length.

There is no way for the program to know how much volume the port takes up. For it to know that it would have the know the thickness of the material the port is made from and how its configured inside the box in terms of corners/bends/etc all of which affect how much volume the port uses.

Its easy to know the net volume of the box before you start. If I have a sub that needs 2.0 cu ft of volume then that's my net. I then add in the speaker displacement and port displacement afterwards to get my gross volume.

[bkolfo4]

Programs such as http://www.carstereo.com/help/Articles.cfm?id=31 account for port displacement as you increase the length of port. The only thing you have to account for before hand is the sub displacement. No reason in trying to figure out net volume before calculating your port.

No.

[775Tundra]

the program tells you the port length after you tell it the volume and desired tuning. There will be no way for you to know the net volume before the program advises a length.

There is no way for the program to know how much volume the port takes up. For it to know that it would have the know the thickness of the material the port is made from and how its configured inside the box in terms of corners/bends/etc all of which affect how much volume the port uses.

Its easy to know the net volume of the box before you start. If I have a sub that needs 2.0 cu ft of volume then that's my net. I then add in the speaker displacement and port displacement afterwards to get my gross volume.

You make some good points. I may have been using it wrong. I just read it over and over and maybe it's the wording. I will compare the numbers to the re calculator just for my own peace of mind. Thanks.

[775Tundra]

Programs such as http://www.carstereo.com/help/Articles.cfm?id=31 account for port displacement as you increase the length of port. The only thing you have to account for before hand is the sub displacement. No reason in trying to figure out net volume before calculating your port.

No.

Wow. Your convincing.