# Ported box creation - maybe a dumb question - port size?



## Bugs78 (May 14, 2010)

Since I've started building my own boxes (8-10 years ago), ive run nothing but sealed boxes. Simple to construct, and sounded awesome.

Im tempted to go ported this time, if space permits.

Basically, the box will be limited to a specific size. Once I design the size of the overal box, is it then possible to 'figure out port size' based on this box? Can all boxes be ported? 

It will be a rectangle. Roughly 1.5^ft. inside the box. Sub will be facing down towards the floor

(about 38wide x 8deep x 13height if the specifics make any difference).

How to I go about determining what size port i need to use, and how long of a port, and where physicall on the box would the porrt? 

going by the picture i've included, is it possible to use a round port on panel #3 or does it have to go on the panel #1? Would i need more then one port? would a large wood vent on panel#1 be a better choice? 











also, the sub is a JL 12W3v3-4 if it makes any difference at all


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## Oliver (Jun 25, 2007)

Have a sealed box made that way for you.

A ported enclosure is designed around the T/S specifications.

... or U could just throw it together as U mentioned and go: *JL Audio subs sound like **** !!* :laugh:


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## Bugs78 (May 14, 2010)

a$$hole said:


> ... or U could just throw it together as U mentioned and go: *JL Audio subs sound like **** !!* :laugh:


Im more then capable of building it myself, thanks. And also, thanks for the glowing review of my equipment that I never asked you for.

Now back to the question at hand. Is there a way to calculate adding ports to a specifically sized box, or do the ports come first and box built around it?


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## Oliver (Jun 25, 2007)

Bugs78 said:


> Im more then capable of building it myself, thanks. And also, thanks for the glowing review of my equipment that I never asked you for.
> 
> Now back to the question at hand. Is there a way to calculate adding ports to a specifically sized box, or do the ports come first and box built around it?


The speaker come first, then use the box building program of your choice to design it.

You need to know what to do, before you start ... it's complicated.


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## Oliver (Jun 25, 2007)

Plan B

just build the box to whatever size will work and use a 3" PVC pipe...the longer the pipe the lower the tuning


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## Bugs78 (May 14, 2010)

a$$hole said:


> Plan B
> 
> just build the box to whatever size will work and use a 3" PVC pipe...the longer the pipe the lower the tuning


This is sort of what I expected to do. I realize retro fitting a port into a sealed style box may not be ideal. 

Any issue you forsee having the port on the same side as the sub vs ported out the end?


Odds are I will build the sealed box, as per usual. If im not happy, I will do some testing with different round ports. See what sounds decent. Not like I will be doing any competitions. Purely for personal entertainment. Just want a bit more kick then the normal sealed boxes give. That said, im throwing a bit more power then usual this time.


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## 89grand (Nov 23, 2006)

There's more to ported enclosures than just the tuning frequency, tuned by the length and diameter of the port. You may build an enclosure, and assuming you can fit the port, tune it to whatever you want, but that doesn't mean it will sound good. Using too small of an enclosure will result in funky ass frequency response regardless of what the tuning frequency may be.

Try modeling some enclosure in something like WinISD and you'll see what I mean.


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## Oliver (Jun 25, 2007)

Here's an idea: :bulb2:



Specifications

3/4" MDF Construction

12W3 subwoofer, might need an 11-1/8" cutout

Exterior Dimensions - 26-1/4" x 14" x 11-1/2"

1.8 cubic feet

Seal it air tight

The vent tube could be adjustable in length which would allow you to tune the box to your own personal preference

PE sells vent tubes


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## Bugs78 (May 14, 2010)

a$$hole said:


> Here's an idea: :bulb2:
> 
> 
> 
> ...



The problem is more the car and design then it is build. 

Im currently car shopping, but doing some research and buying bits of stereo before I actually ge tthe car.

The one top of the list is currently an 05-06 cooper S. Plan is to basically build a box in the cavity behind the back seat but only 8" tall or so, so that I can put stuff on top of it as need be. (yes I know these cars are tight, ive owned one before). My old box seen below worked well, but I want to change things up, and fire down so I can use the entire top of the box without having to see grills or worry about stuff on the woofer.










Ignore the mess, I was still tuning and installing during this pick. Sadly never took a finished pick. Basically i want to rebuild THAT box, as short as possible, yet make the sub fit ok, and fire down to gain a pinch more space.

If I indeed do get the cooper, I will be extremly limited. If one of the other cars wins out, then my optioins change, but right now, MINI is the front runner, so im virtually planning for that.

Current setup is
Kenwood XR-4S - 4channel (4x120)
Kenwood XR-1s - mono (4ohm 600watts, 2ohm 700watts)
Focal 165VR components for front

Planning on picking up a Kenwood KDCX994 between now and september (when I actually buy my next car).


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## Oliver (Jun 25, 2007)

Why not use a 3" stand-off [ a tube that will hold something in a certain postion ] and cut a piece of something to go above the sub that can support some weight?

ex: wood, plexiglas, etc..,

cut it to the size you want to throw your groceries on !


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## DaveRulz (Jun 22, 2006)

Yeah, you can still fire up and have an invisible grille (using less overall height) There are several people who have done false floors here with hidden grills, including myself:





































This box only ended up raising the floor about 4-5 inches, and kept the spare tire accessible.

Also, don't forget that the space that the subwoofer and port displace inside the box do not count towards the total volume of the enclosure. JL recommends a 1.75 cubic foot ported enclosure, so with a little over 1.5 cubic feet gross, after port and speaker displacement, you're getting pretty far from the spec. You could go external with the port to maximize your enclosure space, maybe you have room to snake a piece of 3 inch PVC around the trunk that won't interfere with groceries. I think you'll be better off going sealed since you clearly don't want to sacrifice the space for a ported enclosure. Also, in a mini, I'd assume a 12 sealed would get plenty loud (yes I know more is always better).


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## Hondakilla98 (Apr 2, 2010)

Well to determine port size try this calculator.
PORT Size Calculations and Formulas for WOOFER and Subwoofer BOXES
There is also a vent length calculator on that page.
Another good tool to get an idea of where you'll be tuning wise is the Re sub box calc here.
http://www.reaudio.com/speaker_box/LPort_Box_Calc.html\

So figure out how much port area you need first, then use the re calc to make a box that will fit your dimensions. And see where you end up volume wise. I'd suggest a tuning in the low to mid 30's. My box is tuned to 30 hertz.


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## Oliver (Jun 25, 2007)

Square to round and vice-a-versa >>> PORT Size Calculations and Formulas for WOOFER and Subwoofer BOXES


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## Hondakilla98 (Apr 2, 2010)

So I got bored and modeled it. JL reccomends 1.75 net with 17 sq in of port area. I used the re box calc to design a box to make you and JL happy. It's 30x13x10 with a 1.5"x11.5" slot port. 17 sq in of port area and tuned to 30 hertz with 1.73 net cu ft. So if you can lose 2 more inches of space you can run ported. Put those dimensions into the re calc and it'll even give you cut dimensions on your panels. And If your going to fire the sub down, I'd run the port up.


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## Oliver (Jun 25, 2007)

a$$hole said:


> Specifications
> 3/4" MDF Construction
> 
> Exterior Dimensions - 26-1/4" x 14" x 11-1/2"
> ...





Hondakilla98 said:


> So I got bored and modeled it. JL reccomends 1.75 net with 17 sq in of port area. I used the re box calc to design a box to make you and JL happy. It's 30x13x10 with a 1.5"x11.5" slot port. 17 sq in of port area and tuned to 30 hertz with 1.73 net cu ft. So if you can lose 2 more inches of space you can run ported.


Nice of you to help, Hondakilla98


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## Hondakilla98 (Apr 2, 2010)

No problem. I've learned quite a bit from stereo forums, and It's always good to help when I can.


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## Bugs78 (May 14, 2010)

thank you all very much for your help. Definately gonna try and build some boxes. typical car audio nut = always have spare 3/4 mdf laying around.

thanks again everyone!


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## Bugs78 (May 14, 2010)

Hondakilla98 said:


> So I got bored and modeled it. JL reccomends 1.75 net with 17 sq in of port area. I used the re box calc to design a box to make you and JL happy. It's 30x13x10 with a 1.5"x11.5" slot port. 17 sq in of port area and tuned to 30 hertz with 1.73 net cu ft. So if you can lose 2 more inches of space you can run ported. Put those dimensions into the re calc and it'll even give you cut dimensions on your panels. And If your going to fire the sub down, I'd run the port up.



this is perfect. 

13 gives me my sub panel to cut the hole from.
30 is certainly going to fit between the left and right side. Just make a trim panel to finish the gap so it looks solid from end to end.
10 - only giving up 2" in height is fine. 8 wasn't realistic, especially firing down.

again, thanks dude. My brain was futzing around with those calculators. I can build anything, but getting my head around the tuning, and port configurations just wasnt making sense.

more i think about it, the more everything firing up is looking necessary. im assuming runnin the port AND the sub up wont be an issue?


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