external port

[JBano13 0]

If I hsve aeroports half internal half external does the volume of the external portion of the port count towards the internal volume of my box? Also would the surface area of the portion of the port within the box divided by 1728 by the ports displacement? Thanks in advance!

[ppiflat10s 3]

surface area of the port is just using the face of it, nothing to do with the volume. so if its a 3" port, its pie*r^2 or whatever the formula is for the area of a circle. and to get the internal volume of the box, you take the inside measurements and multiply LxWxH, divide by 1728 and theres your gross volume, then you take the displacement of the sub off of that, and then you take the surface area of the port times the depth of it inside the box, divide that number by 1728 to get the port displacement, and then after you subtract sub/port displacement then you have your net volume.

[JBano13 0]

surface area of the port is just using the face of it, nothing to do with the volume. so if its a 3" port, its pie*r^2 or whatever the formula is for the area of a circle. and to get the internal volume of the box, you take the inside measurements and multiply LxWxH, divide by 1728 and theres your gross volume, then you take the displacement of the sub off of that, and then you take the surface area of the port times the depth of it inside the box, divide that number by 1728 to get the port displacement, and then after you subtract sub/port displacement then you have your net volume.

I think you understood me wrong, I understand the whole displacement thing I just wanted to make sure I was right. The big question I am asking is whether or not the internal volume of the external part of the port can be added to the net of my boxes internal volume? I hope that sounds right.

[ppiflat10s 3]

not even the internal volume of the internal part of the port is calculated into the box volume. dont worry about the external part of the port for any other reason than to get the port to the right length, and only subtract the displacement of the internal part of the port.

so the airspace inside the internal port section (as well as the displacement of the port wall) gets subtracted from the boxes volume, not added on.

hope thats clearer.

[JBano13 0]

I think I get what your saying, I guess I should have figured that out before building my box. So I'm short on internal volume by whatever the volume of the cylinders (the aeroports) are? I guess you live and you learn.

[jcarter1885 995]

I think I get what your saying, I guess I should have figured that out before building my box. So I'm short on internal volume by whatever the volume of the cylinders (the aeroports) are? I guess you live and you learn.

Just add that to the displacement with your subwoofer, bracing(if any) and it shouldnt change things by that much (your box volume and tuning frequency will be different from what you first calculated). If it is not to your liking then build another box and just make it better, not that big of a problem.

[KU40 173]

Only the volume of the aeroports that is inside the box counts as displacement when figuring box volume.

[ppiflat10s 3]

I think I get what your saying, I guess I should have figured that out before building my box. So I'm short on internal volume by whatever the volume of the cylinders (the aeroports) are? I guess you live and you learn.

Just add that to the displacement with your subwoofer, bracing(if any) and it shouldnt change things by that much (your box volume and tuning frequency will be different from what you first calculated). If it is not to your liking then build another box and just make it better, not that big of a problem.

my most recent box I built, the port displacement was .7 ft^3, had I made the box the correct size including the port, and having the port take some of that away (granted only half of his are in the box, so take off .35) it would have raised my tuning from 35 to 40 hz. and he has 2 ports so they need to be longer to keep tuning than if he had one, so he likely has a worse scenario than my situation would have been.

but the box is already built so might as well put it the car and see how it sounds before you build another one. of course if you have room and can add onto the length of your ports outside of the box it will lower the tuning some.