wft!!! box problems

[gmsierra2000]

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.

yeah you just took my confusion level form 5 to an 8 lol its all good man. I guess I just need to help understanding why my port is way to freakn long for my box at 3" port width.

[Sergeant_Skyrim]

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.

yeah you just took my confusion level form 5 to an 8 lol its all good man. I guess I just need to help understanding why my port is way to freakn long for my box at 3" port width.

I'm going to try to explain it simply.

There are 3 things you can do to lower tuning:

1. Increase net box volume.

2. Increase port length.

3. Decrease port area.

You can also do the opposite of these things to increase the tuning of the box. It's all a sort of 'balance' in the end. Your internal port area is 16.5H x 6W for the both of them. This gives you 99 square inches of port area. In order to combat a larger amount of port area (I am in no way saying this is TOO MUCH port area for your instance, just assuming we start with a baseline of 0 port area), you must either increase net box volume or increase the port length. Let's assume that you also increased your net box volume from 0 cubic feet to whatever it is now. Now you have a certain tuning frequency, but it's way higher than the 30hz you want. It's the equivalent of just cutting a square hole in the face of your box actually. The last thing you can do to give yourself a lower tuning is to increase the length of this port. It has to be increased to a certain length to provide you with the 30hz tuning you're after.

Hope this makes a little bit of sense, I just woke up haha. You don't have to tackle it in this order either though, you can go about doing it however you want. Just remember that it's a balance though. If you change one thing, something else is likely to change until you find the right ratio.

[gmsierra2000]

I kind of understand it but my main question is, if my outer diameter box is 30"W x 20"H x 17"D using 3/4 mdf. if I enter the numbers in the 12volt calculator for box it come up with 4.7 cubic ft. now after getting a number for mu port over all length how do I combine them together to figure out cubic ft after adding my port. port width is now 2.5" wide per box.

[gmsierra2000]

sorry if it seems like you guys are repeating these things to me but I truly don get it lol, however I do want to learn

[Guest]

you guys are forgetting about the Torres box calc that's on this forum. best calc imo

[gmsierra2000]

never used it before. and seams like you would need to know all the information pertaining the box and port so you can plug them in that forum, if I had all that information then what's the use of plugging them in that program? just a question.....

i'm just trying to figure out with a box of outer diameter 30"W x 20"H x 17"D using 3/4 md with a 2.5" port width opening. how long does the over all port length has to be to tune the box at 30 Hz

[Sergeant_Skyrim]

never used it before. and seams like you would need to know all the information pertaining the box and port so you can plug them in that forum, if I had all that information then what's the use of plugging them in that program? just a question.....

i'm just trying to figure out with a box of outer diameter 30"W x 20"H x 17"D using 3/4 md with a 2.5" port width opening. how long does the over all port length has to be to tune the box at 30 Hz

I can actually try to give a more in depth answer sometime this weekend if you like, I'm about to head out for class and work tonight right after class wish I had seen this earlier haha. A good thing about the calculator is that you can plug in random numbers for your box and port and play with different ideas and see what your tuning comes out to without actually having to do the math and all yourself. You can see what changes when you change one number and all that.

If you download the Torres Calc for instance you can plug in your outer dimensions for the box, using 3/4 mdf and plug in your port width and height. Then play with the length and continue to change it until you get to 30 hz. It'll do all the math for you. Keep in mind though that the longer you make your port, the more box space it'll take up. As you increase port length you may find out that you need to also increase the dimensions of your box to give it more net volume and keep it within whatever specs you wanted in the first place.

[Guest]

well first off you have 4.73 cubes with those dimensions. 3.7 cubes after woofer displacement of two woofers (each .54 cubes).

manual says optimum box specs PER WOOFER is 2.6 to 3.25 cubes per woofer. you barely have enough space for one. let along two.

[gmsierra2000]

i can always increase my dept a bit if needed height and width has to stay the same. and is sub forward port forward the best set up in a truck or should it be port up sub forward or port up sub up?

[gmsierra2000]

Torres box calc is pretty awesome. how accurate is this thing. question. is the net volume the overall cubic ft of the box after the install of the port?