Sub box tuning help

[bigbud747 10+ year member]

I am going to build another box for 2 18's (Fi Bl's). It will be 10.81 cubes after sub displacement. I figured that I will need about 158 sq. inches of port area. The port itself will be 3.55" tall and 44.5" wide. My only question is, since I want the box tuned to 34hz, how long do I need to make the port? Or, is there a site that will tell me how long to make the port if I put in my figures?

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[bigbud747 10+ year member]

Well, I didn't even think to check the RE box calculator. And say so if I'm wrong, but when I put in my dimensions (with a port 44.5" tall and 3.55" wide) and I made the Port L2 4.75" long, it got me a 34hz tuning on the box. I'd still like some input on whether this is right or not.

Thanks.

 

[PV Audio 5,000+ posts]

I wouldn't trust the RE calculator if my life depended on it. Why did you chose those port dimensions? The larger it is, the more square you should make it. Round is the most efficient, but rectangular ports that are very tall or wide but very thin usually suffer bad compression which lowers the enclosure's efficiency. As a result, you lose output which I know you don't want if you're running dual 18s. Instead, try something like 12x12 or 13x13 or mix the dimensions for a more square rectangle. If you need anything beyond that, PM me and I'll help you out.

 

[bigbud747 10+ year member]

If you look at the box I made for the extended cab ranger with 2 18's in the build log section, you would know why I want to make the port 44.5" wide and 3.55" tall. I've seen many builds with the same layout and design as my box, with the port at the top of the box, all the way across, and about 3-4" tall. And for the simple fact that it looks better to have the port at the top all the way across than a big 12"x12" port in top middle part of the box.

 

[RAM_Designs 5,000+ posts]

What PV said. Not only do you lose efficiency, you also have to make the port longer as a result of having it skinnier. A 1:5 ratio is about as skinny as I go with my ports...more square, the better.

 

[PV Audio 5,000+ posts]

If you look at the box I made for the extended cab ranger with 2 18's in the build log section, you would know why I want to make the port 44.5" wide and 3.55" tall. I've seen many builds with the same layout and design as my box, with the port at the top of the box, all the way across, and about 3-4" tall. And for the simple fact that it looks better to have the port at the top all the way across than a big 12"x12" port in top middle part of the box.

Suit yourself, do what looks best to you. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[bigbud747 10+ year member]

Well, after consulting with another guy a little bit ago, I think I'll make the port 30"x4.5". Now, the only thing I need to know is how long to make it.//content.invisioncic.com/y282845/emoticons/uhoh.gif.c07307dd22ee7e63e22fc8e9c614d1fd.gif But to make things easier on me in the future, and you guys that have helped, I want to know how you figure how long to make the port, putting into consideration the box volume and sq. inches of port, so I don't have to keep asking on here how long to make the port.

 

[RAM_Designs 5,000+ posts]

I want to know how you figure how long to make the port, putting into consideration the box volume and sq. inches of port, so I don't have to keep asking on here how long to make the port.

http://www.carstereo.com/help/Articles.cfm?id=31

VERY easy to use.