plan of my twin 15 box,does it sound ok?

hi im new here,and also new to car audio(im 16 years old)
i recently purchased 2 x GTO1502D 15's(300w RMS) and a Boss CX950 amp to power them. I've tested them free air and they have some pretty good excursion so I'm dieing to get them in a box.
I'm going with a ported box as i want the nice rumble bass more than a punchy sort of bass.
i used the calculator on this site to help me design my box as well as google sketch-up(I'm a visual person) but things don't seem to look right.
First of all is my box size acceptable for 2 15's?
I'm plan on tuning to 33-36 hz so i used the calculator and it says i only need a port that's around 6 inches long, that to me seem way to small(but the fact the ports height is 15" may have something to do with it)



thanks in advance

Hey Ratgreen, it is normally suggested to use .75 MDF for a box that size. So, I will recommend using .75 MDF first of all. Second it is also suggested to separate the chambers in case of a woofer blowing and causing the active woofer to use the entire box volume, it also provides some bracing. You will have to brace the box as well.

By my calculations, using .75 MDF, you will have a internal box volume of 6.52 cu ft. with the port and driver displacement taken into account. That is assuming your driver's displacement spec is .07 cu ft., and using .75 MDF your port is .18 cu ft displacement. You would still have to take into account your bracing displacement as well for the final figure of box volume, however you decide to brace it.

By the figures I laid out above you should be closest to 34hz tuning.

good luck.

Oh, those woofers call for 3.5 cu ft. per box. So I would shoot for a depth of 21". That will give you a box volume of 7.62. Minus the driver's and port displacement of .32 cu ft. and that gives you 7.30 cu ft., brace the mess out of it and it will give you the 3.5 cu ft. per woofer.

You would be closer to 32hz with a 6" port with these specs, so might want to make it a slightly smaller port if you go this route.

ratgreen, use pencil and paper to satisfy your thirst for visuals.  I think that computer-aided graphics can lead to premature satisfaction of entirely poor designs (because they look so pretty).  Spend more time on learning the basics (such as the relationship of port opening size to port length), and you should either use the manufacturer's recommended box type / size or learn to use WinISD.  Methos123 was quick to find your early misstep in calculating for 1/2" baffle thickness.

-------------
Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

All good recommendations so far. The first thing I saw that didn't look right was the port design. 2 inches is WAY to small for those subs. Like stevdart said, you should download WinISD and mess around with that. You can look at the air velocity through the port to make sure that you won't be having port noise. You will have port noise if you have too high of an air velocity through the port caused by too small of a port cross sectional area.

methos123 also had good advice about using bracing, seperate chambers, and 3/4" material. I may also suggest a possible double front baffle to add support. Basically you would just have two pieces of 3/4" MDF together to give you more support.

thanks for advice guys,

so i need to make it with 3/4" (im used to mm sorry)
add 1 inch onto the size(so its 21")
double up the front of the box
bracing(i forgot to say that in first post)

im still only confused about the port size, surely 2 X 15 inches is enough, if not then would 3 X 15 inches be sufficient?

Ratgreen, you need to add 2 inches to the depth is what I was saying. Right now you have a depth of 19 inches. If you can't sacrifice anymore depth, then use height or width. I don't know if it will change things if you use height or width instead of depth. I don't have time right now to see because I'm heading to the mountain. (: I will look more into it later, maybe someone else can get to it before me.

If you raise your height or depth 2" you will be alright. But, you would have to raise your width to like 42" for the same space gain. (2.58 for height and width, 2.62 for depth.) So, I recommend you either raise your height or depth by 2", that will give you some bracing room to use as well as the board that separates the chambers.

Oh, and I am an idiot (that is a screen name for someone else) recommended me to round of the back and front of the port to eliminate port noise on my box a while ago. My box was already done by the time he mentioned it, so I went ahead and left it alone. Luckily I didn't need to round off the edges, but it is still something you should keep in mind when building your box.

On WINisd with my Kicker drivers (I am not sure if the driver makes a a lot of difference for this purpose) I plugged in a box volume of 7 cu ft. tuned to 33hz, square vent of 3" x 15" and it gave me a length of 9" and vent mach of .07. That is acceptable. As far as I know, anything under .10 is acceptable.

The slot port calculator on this site says to make it 10.4 inches long for the same thing.

Your goal should be to shoot for a box volume of 7 cu. ft. with the bracing and separate chamber board added. Don't forget to take the driver's displacement off too.

Sorry about this: (2.58 for height and width, 2.62 for depth.)

I meant 7.58 and 7.62. (:

cheers for your help methos,

when you say the separate chamber board,were would this board end in relation with the space from the port( so that no port noise would be made)

I don't have much time right now, but the separate chamber board would have to go in the middle. You will have to work the ports around the woofer cutout and the middle board. You will have to have 2 ports, one for each chamber. Think of it as 2 separate boxes when figuring the volume and port length/size. Let me know more about your available room to work with... L (depth) x W x H of your maximum space available.

well i finished my box a while ago and forgot to post the results

im happy with how it turned out, enjoy

https://www.youtube.com/watch?v=IEqjh9ng3so

12 sq in of port area per cu ft is a good start

-------------
Custom Enclosure Design