How does an external port work?

[robby512]

So I'm trying to build a box for four sundown x18 and I'm running out of room the port is taking up a little more room and I could use it.

So let's hypotheticly say the box is 12 x 12 x 12 and my port is 1 inch wide by 12 tall and that is an internal port so if I make it an exterior port I do the same thing? Just outward? And what if I do Half in and half out then what just like it says half in half out?

[twisted1]

Yep. I've seen it alot on burp boxes

[CleanSierra]

That's a terrible aspect ratio 1:12. And 1" wide port is asking for port noise. I know you're asking like in theory but that example is definitely one that would not work well.

As far as displacement of the port goes and tuning, you just have to calculate that with old fashioned math.

[CleanSierra]

1:1 is the most ideal port aspect ratio. One of the factors that makes an aero port so efficient, plus the fact that it's got some good cross sectional area and the flaring helps bunches as well. If you can stay below 4:1 on the height:width of the port, that's best. The closer you get to 1:1, the more efficient. That is assuming you have the proper amount of port area to satisfy the cone area, tuning and Xmax

[robby512]

Yea just figured it would give me close to 2-3 cubes back and I ment to do a rectangular exterior port that somewhat goes between my seat.

I don't just want something for burp I want it to be a daily driver that will work the same right I don't see why it won't. Hm aero port is something I didn't think of aero ports take up less cubes correct?

[CleanSierra]

Yes, they will take up less space typically. It can be tricky to get the proper tune while still satisfying proper port area. A lot of guys think, "an setup aero port is super efficient, I can use way less port area". They defeat the whole purpose of taking ADVANTAGE of the aero port haha. Getting the right tune and port area can prove tricky, that's the only downside to the aero.

[alaskanzx5]

Aero ports do take up less area. Easily changed for different tuning freq.

[robby512]

Ok hmm thoughts I kinda jumped into buying these to soon cause it was a great deal and got rid of my 2 15. I'm only down by a cube or so I really want to find a way to hit there rec of 5.5 per sub before displacement. So back to the drawing bored with more ideas how big of an aero port would I need for those 4 18?

[alaskanzx5]

Sonotube, can be squezzed to form an oval rather then a circle, still a round port that can be flared with wood trim rings cut to the size and shape then a round over but. Cheap and effective. Come in all different sizes.