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Ported Box Design: A Tutorial *Updated 6/30*


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Alright, so I see a lot of posts around here that say things such as “can someone help me design a box?” or “I don’t know how to use Torres.” So I am writing this guide to act as a one stop resource to learn how to design a simple box. This guide will teach you both slot ported designs. I am hoping it will go over all the basic information you need similar to the for dummies series of books.

**Preperation**

To start off you will need some software. Torres box designer and Google Sketchup are the programs we’ll be using in this tutorial. I have also used Inventor in the past but it is much more difficult to learn and a very expensive program. The free version of Sketchup has all the features we need.

There is a write up on how to get Torres Box Calculator in the enclosures section of this forum so I will go right to downloading sketchup.

Start by googleing “Google Sketchup and it should pull up this page:

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Go ahead and click on “Downloads” and it will bring this up:

56803367.png

Click on the big blue button in the top right corner that says “Download Sketchup.” From there it should guide you through the download and installation process.

Now that we have both Torres and Sketchup installed we can get to the actual box designing.

**Calculating**

For this tutorial we will be using a Sundown SA8v2 but I think you will get the idea and can use the principles to design boxes for different subs.

Pull up your subwoofer band’s website and navigate to the enclosure recommendations for your specific subwoofer.

If you are using multiple of the subwoofers then you can just multiply the recommended ported volume by the number of woofers.

22457497.png

Example:

1 SA8v2 is recommended at 0.5-0.75 ft^3

Therefore 2 SA8v2s need 1.0-1.5 ft^3

And 3 SA8v2s need 1.5-2.25 ft^3

Remember this number as it will be used soon.

Next, go into Torres and enter in the outside dimensions of the box you want to build, these can be obtained by measuring your trunk and making them up. For this example our box will be 9 inches tall, 24 inches wide and 12 inches deep.

92378701.png

Entering those numbers spits out our net volume; highlighted in red. It is above the enclosure recommendations but that is fine for now as we have not yet accounted for the port.

After that, enter the displacement of the woofer into the box labeled “woofer displacement,” this number is also available on the website of the subwoofer manufacturer.

The easiest and most often built box is a box with 3 common port walls. Start from here and you can get more and more complex designs as you learn. So enter 3 in the box for “# of common port walls.”

38012508.png

Now it’s time to start designing the port!

For the height of the port take your overall box height (9) and subtract 1.5 (.75 for the thickness of each the top and bottom, .75+.75=1.5) which gives us 7.5.

As for the width, find a number that gives a good ratio of height to width so that you don’t a super skinny tall port or something like that. I’m not sure if there is a more accurate way to find this, if there is lemme know.

Once those numbers are in, play with the length until you find one that gives you the tuning you like. We’ll use 33 Hz as an example, because that’s what everyone wants to tune to. You know what they say about 33 Hz…

65773915.png

Hold on! There is a trick; you must ensure that your Port area is within the port area range listed in the box directly above it.

94607407.png

In this case 9.38 is within the range of 9-12 so we are good to go.

Next, double check that your Net volume is within the Manufacturer’s recommended enclosure specifications that we looked up earlier.

34086532.png

Our net volume came out to 0.77 ft^3 and we were aiming for 0.5-0.75 ft^3, so we are just barely above but it will come down a little later when we account for our bracing.

If everything checks out in Torres then you are ready to move on to the design phase.

**3D Design**

Open up your newly installed Sketchup.

Grab the rectangle tool, and then click first in the origin (where the red, green, and blue lines meet).

Type in the dimensions of the base of your box with a comma in between (“24, 12” in this case). Then press enter to draw the rectangle.

85447710.png

Now we are gonna use the Push/Pull tool to grab the rectangle and pull it up ¾ of n inch for the bottom piece of mdf. So click on the tool, then click on your rectangle, then start to pull upwards. Once you see it start to raise then type “.75” and push enter.

67099722.png

Next we are going to draw on the walls. Click the offset tool and click on the top face of your box. Once you see it is offsetting on the inside of the box rather than the outside you can type “.75” and puch enter.

You should now have this:

90132809.png

You can use this outline to start drawing the walls of the box and port.

Start by deleting the front interior wall line highlighted in blue.

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Then extend the right wall to the edge of your box.

You should now have this:

58721508.png

Now we can start designing the port.

Start with a line that is half the port width away from the interior right wall.

In this case it is 5/8s of an inch because the full port width is 3/4s of an inch, shown in blue.

56563470.png

Next we will draw the port centerline.

Start from the point you found and draw a line towards the back of the box. End half your port distance from the back wall.

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Take your port length that you entered into Torres and subtract the length of this line you just drew. So 27-10.625=16.375

This is the length of our extension.

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The two lines highlighted in blue are now the centerline of your port.

You can add lines 5/8 of an inch inside of this now to create the other side of your port.

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This is what you should have.

Now add the other edge of the port.

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Now you can go back and delete the centerline of the port.

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Now you see the design starting to come together.

Add the front wall back on and finish off the edges so that you can see where the pieces of mdf come together.

42728331.png

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Now go ahead and draw the 45s into the corners

I draw my 45s with each leg (in blue) 1.25 inches long.

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And here are all the 45s.

87053571.png

Then draw your round-overs in.

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Now we are ready to pull all of this up 7.5 inches. This is the total box height minus the 1.5 (.75 for each the top and bottom)

92552040.png

WooHoo! Starting to look like a box!

Now we will make the cutout for the woofer. This dimension can be found on the manufacture’s website or in the user manual.

Draw an X across the front of the box to find the center, then draw a circle the size of your cutout.

51408506.png

Then use the push/pull tool to push that back .75 to cut it out.

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Now what we are going to do is select everything and make it a component, this way the top can easily be hidden so you can see inside your box.

Push Ctrl + “A” to select everything.

Then right click on the box and go to “Make Component”

17899286.png

A menu will pop up and you can name it.

We will name it “Box”

Then press create.

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After that, we will draw the top.

Draw a rectangle from the back left to the front right covering the entire enclosure.

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Use Push/Pull to raise it .75

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Right click on the box and click “Hide”

It will disappear, but don’t worry; it’s not gone!

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Then select all again and make the top a separate component the same way we did the box.

We did this so that the top of the box can easily be hidden/unhidden without individually selecting the faces.

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Go to Edit > Unhide > all

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You are now done with the 3D design of your box!!

**Final Stages**

Basically all we have left is to account for the bracing displacement. The round-overs we did have such a small impact on volume that they can be ignored.

Here is a closeup of the 45s.

83520149.png

The area is .5(base)(height)

So the area is (.5)(1.25)(1.25)

=0.78125 inches^2

We then multiply the area of the base times the height to find the volume of each individual 45.

0.78125*7.5=5.859375 inches^3

Since there are 5 corner braces in the box we multiply this by 5.

5.859375*5=29.296875 inches^3 for all the braces.

However Torres needs the bracing displacement in Feet^3

12^3=1728

So there are 1728 inches^3 in one foot^3.

Then divide your total displacement volume by 1728 to find how many cubic feet they take up.

29.296875/1728=.017 feet^3 (wait till this step to round your numbers.)

Put .017 into Torres and it will give your final box specs:

22789795.png

This is the final spec sheet for the box.

You can see the net volume came out to within the recommendations (exact lol)

The final tuning is 33.34Hz.

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You’re done!

Go build your box now.

This was supposed to act as an all together guide on how to design a simple box from start to finish. Although you may not be designing the exact same box you can follow along the steps to create a custom box of your own. Now nobody can say “I don’t know how to design boxes.”

Anything to add just let me know.

Thanks!

***Update: Designing the 45s in your port***

Its has been brought to my attention that some changes need to be made.

In the corner of the port a perfect 45 would be a 1/4 circle that kept the port the same width the entire way. If it gets smaller, this is called "bottle necking." This would be difficult so that is why 45 degree boards are used. When designing your 45s you have to make sure that the corner of your port stays at least the width of your port wide.

Imagine this being the corner of your port.

66310105.png

Grab your offset tool and click on the curve, then drag over towards the other side of your port. Type in the exact width of your port and push enter. This will draw a scaled radius that would be the ideal 45.

So when designing the 45 you want it to be OUTSIDE of this curve.

You can see in the next picture which design is right and wrong.

54875982.png

I think you can get the idea from that picture. Haha

***Update: Check post #16 for how to account for port flares***

***Update: Check post #25 for how to draw aero ports and how to draw aeros with flares***

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Thank you sir, that was very helpful as I know how to use torres but I couldn't figure out Google Sketchup.

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Lots of good info here. I wish that when I first used SketchUp there was a tutorial like this, well done sir. Only complaint I have is that your port is slightly incorrect in that the corner bend and 45 is bottle necked. Also that the Port , both of which flare are not accounted for in the calculations.

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Awesome writeup. This should be stickied imo

On 5/8/2011 at 7:38 PM, Kranny said:
On 5/8/2011 at 7:35 PM, 'Maxim' said:

It hurts me inside when I read stuff like this and remember you're 15

LMFAO so true

:blush:

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A very simple design haha good start. If only they were all that easy ;)

Just say no to Ground Pounder Customs.

More box builds

some cars do over 170db with one sub, so clearly my two 12"s can do that in my car, with my knowledge too! look out bitches!

I'm with captain stupid.

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Don't take said i said personally. I didn't mean to offend, just trying to add a little more info.

Example*

Technically the 45 would need to be a 1/4 circle to be 100% accurate. Or just 45 the left wall of the port a bit to make up the 1.25in gap. Also for the flare all you would do is measure the additional space added to the port. Think of it as the opposite of a 45, just add that volume of air space into the port tuning calculations. Its not really THAT big of a deal but if your trying to tune to an exact frequency then it will matter.

* Eclipse CD3200 with PAC SWI-CAN2 and SW-ECL2 Steering Wheel Controls Interface
* Pioneer D-Series Mids and Highs ( Fronts: TS-D1702C; Rears; TS-D1702R and Dash; TS-D1002R )
* Rockford Fosgate PBR300X4 ( Mids and Highs Amp )
* DC 3.5k with Dual Inputs; Custom Plexiglass Backing ( Sub Amp )
* Rockford Fosgate Balanced Line Driver

* One FULLY LOADED ~ 10" DC m2 XL
* Custom Built Carpeted Ported Box Tuned to 32hz. Single Chamber With Volume of 1.44618³ ft ; 1.13216³ ft After Displacement
* Custom Built Carpeted Trunk Wall with Added Fans for Amplifier Cooling
* MechMan 240a High Output Alternator

* KnuKonceptz Krystal Kable RCA Cables
* Upgraded Electrical With 1/0 KnuKonceptz Kolossus Fleks Kable and 1/0 Sky High Car Audio Cable
* Five Exide Orbital ORB34M Marine 12 Volt Batteries
* PowerMaster XS D3100 12 Volt Battery

My 2008 Chrysler 300 Limited - SuperCharged 3.5L V6 - UBL

My Old 2005 Ford Taurus - CarDomain - Vehicle Was Sold

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Don't take said i said personally. I didn't mean to offend, just trying to add a little more info.

Example*

Technically the 45 would need to be a 1/4 circle to be 100% accurate. Also for the flare all you would do is measure the additional space added to the port. Think of it as the opposite of a 45, just add that volume of air space into the port tuning calculations. Its not really THAT big of a deal but if your trying to tune to an exact frequency then it will matter.

Don't worry man I'm not offended, I just want it to be right! I will write a little update later this week to fix everything.

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