Center Slot Port help!

[vnisme]

So I came up with this for 2 15's. If I wanted to make this a center slot port, could I simply just move the port over? Most port calculations for 8 inches wide and 15.5 inches high give me a length in the 20's. My question is that since my box is about 30 inches, would it be correct if I just had a straight slot port in the center? instead of having 2 L shaped ports coming together as I see often. My box has to be long because the height is restricted to 17 and width is restricted to 38. I am concerned about the 2 subs loading differently in a side slot port configuration.

[Solo008]

I think because you are moving it away from a wall you need to add 1/2 the port width to the length.

[vnisme]

Okay, Thanks. I had a question about subwoofer "loading". If I were to build that box with the port to the side and cut out 2 holes in the baffle for the subwoofer. Would the subwoofer closest to the port behave differently?

[Solo008]

I would say not enough to matter. That will be a tight fit getting two 15" woofers in 30" of space!

[DLHgn]

I couldn't answer you question about loading but as for the center slot port it shouldn't be all that much different in terms of length. The end correction will be different due to it now being a 2 common wall port instead of a 3 common wall but I wouldn't just go with the "1/2 the port width to the length" thing. Rules like that don't take into account other factors and could lead you astray and honestly an inch or two won't drastically change your tuning. I would wait for someone who could tell you the appropriate length (I don't have the proper equations on hand) and answer your question about loading.

[Solo008]

I couldn't answer you question about loading but as for the center slot port it shouldn't be all that much different in terms of length. The end correction will be different due to it now being a 2 common wall port instead of a 3 common wall but I wouldn't just go with the "1/2 the port width to the length" thing. Rules like that don't take into account other factors and could lead you astray and honestly an inch or two won't drastically change your tuning. I would wait for someone who could tell you the appropriate length (I don't have the proper equations on hand) and answer your question about loading.

http://www.jlaudio.com/header/Support/Tutorials/Enclosure+Ports/Tutorial%3A+Enclosure+Ports/287541 Take a read then tell me what you think!

[MADVIBES]

are you afraid to use round ports? round ports generally behave more predictably..

[DLHgn]

I've read that before and is the calculation I use with modification to the end correction. So, I have decided to use the correct end correction for his application and compare it to what you were saying about half and what not.

What RE calculator said: 33.52 Hz

With 3 common wall JL's stock equation: 39.9Hz

With 3 common wall equation with updated end correction: 32.45 Hz

With 2 common wall added 1/2 of port width to stock equation: 37.54 Hz

With 2 common wall added 1/2 of port width to equation with updated end correction: 33.02 Hz

With 2 common wall just equation with updated end correction: 34.6 Hz

This is assuming 11892.5 in^3 net volume, 124 in^2 of port area, 21.25 inch port length (without the 1/2 added)

[DLHgn]

Now these are just what I got. Not set in stone in any way shape or form seeing as my calculations could be skewed one way or the other however my point being that just adding 1/2 the width gives wavering results and rules like that generally aren't the way to go.

[DLHgn]

are you afraid to use round ports? round ports generally behave more predictably..

And efficiency. But they can be harder to implement if you are tight on space