wft!!! box problems

[Guest]

jjj

this is correct. 6" shared/opening, 3" split.

edit: i dont really feel like doing the calculations, but you should have around 12-14 square inches of port area per cubic foot of internal box space. you can find this out by multiplying the width and height of the port opening (the 6 inch width times whatever the height of the port is) then dividing that number by the internal cubic feet of the box.

[Krakin]

Didn't see anyone else say it but last time I checked RE Box Calculator has the wrong tuning calculations.

[bbeljefe]

I haven't used it but I too have heard the RE box calculator is incorrect.

I would use the calculators on the12volt.com if you don't have software.

And look at it like this... for one sub you need x amount of port area and length. For two in the same box, you need double the volume and double the port area. Port length stays the same because the volume to port dimension hasn't changed.

Thus, the center of your port is two ports and when it Ls to each chamber, each becomes one again.

[gmsierra2000]

makes hella logic. so now you guys are saying to use another sub box calculator? what other web site should i use?is winISD any good? iv used it before but got confused on reading the graph. this is why i turned to re box builder

[Facekicker]

You're welcome, I've been holding on chiming in again because I didn't see what your actual box goals were only your rough draft drawing.

Avoid RE Calculator for port tuning calculations, this is what it fuzzes.

Looks like you've got the idea now though.

[bbeljefe]

WinISD Beta is a great program. The others are good as well but I've used Beta for a long time and that's what I like. But, the link I provided to the 12 volt is a good set of calculators if all you want to do is figure volumes and ports.

[gmsierra2000]

so I would go to 12volt and calculate box separate from port correct, if so how do I know if my box will be big enough for the port calculations and should my port width be no smaller then 3" per sub box???

the reason I ask this above questions is because using 12volt square port calculator, if I set my box at 3.1 cubic ft per sub at 19"H x 17"D x 30"W outside dimensions and 17.5"H x 15.5D x 27"W port side and 30" W back of box, ((((((and remember this is per sub. I am calculating one sub box at a time so I can later on build it all as one to have that double port down the middle like the last pic posted above)))))) after putting my port width at 3", port height 17.5", box volume 3.1, and tune 30 hz that equals 44.7port length.

then if I subtract 3" from my width for the bend, that leaves me with 17.5" - 3"= 14.5" before the port turn. so if I subtract that number 14.5" from my over all port length given to me by the 12 volts website

44.7"-14.5"=30.20". so this means the rest of the port would actually close off the box behind the sub leaving no breathing room for my sub port since my overall box width is freakn 30".. what am I doing wrong?????? wtf lol lol

[bbeljefe]

You calculate port area and length based on the net volume you want. Then, you calculate port, driver and bracing displacement and add that to your desired Vb and that's the gross Vb.

And no, there is no 3" minimum width. With slot ports you should maintain less than an 8:1 height to width ratio. Other than that, your ports can be as side or as narrow as need be.

[gmsierra2000]

You calculate port area and length based on the net volume you want. Then, you calculate port, driver and bracing displacement and add that to your desired Vb and that's the gross Vb.

And no, there is no 3" minimum width. With slot ports you should maintain less than an 8:1 height to width ratio. Other than that, your ports can be as side or as narrow as need be.

I don't get it lol im not that advance. im good with numbers though lol

[bbeljefe]

Well let's look at it this way....

Let's say you need (or want) 1 cubic foot per sub and let's keep it simple and use only one sub.

And let's tune that sub at 35 Hz (these won't be accurate numbers, just examples). So you use the port calculator and find out you need an 18" long port with 16in² of area. We can make the port 4" by 4" for 16 total inches of area and let's use ½" material to construct it. That means our port will actually be 5" by 5" by 18". Figure that area, which will be 450in².

Now, you need to add driver displacement, which is usually about .12 cubes for a 12.

In total, we have one cubic foot of volume, .26 cubic foot of port and .12 cubic foot of driver. So our gross box volume must be the sum of those three... or, 1.38ftⁿ.

And in large boxes where you're including bracing, you also have to add the displacement of the internal bracing.

Hope that makes sense, I'm running behind and have to leave so it may not be very detailed.