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Hello everyone,

I'm in the process of building another enclosure and decided to go with an aero port this time.

I know my enclosure will be 18in x 26in x 18in (H x W x D)

Using bcae box calculator that comes to about 3.86ft^3 using 3/4 birch.

I will be using a single 4in aero but I'm confused about calculating it's length for a 25hz tune.

Do I first subtract driver displacement and then figure out my port length?

When do I subtract the port displacement if I don't know how long it's going to be yet?

Am I thinking too much here? Am I missing something? I've got lots of stuff on my mind these days.

 

Also, can the inside flare be 0.5in away from a wall? Or is that too close?

 

Thanks!

 

 

Edited by Wiz Khalifla_85
Dimensions edit

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What kind of sub and what amp?


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18 minutes ago, THATpurpleKUSH said:

What kind of sub and what amp?

JL 15W0-4

It's going to be around 300-350rms @ 4ohms.

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Why are you trying to tune so low? Is this for a car?


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5 minutes ago, THATpurpleKUSH said:

Why are you trying to tune so low? Is this for a car?

Per JL Audio.

http://www.jlaudio.com/15w0v3-4-car-audio-w0v3-subwoofer-drivers-92167

 

I can tune higher too. Just figured it's what they recommend. Personally I like 30hz tuning.

Edited by Wiz Khalifla_85

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.5 inch away from the wall (if it's facing it) is wayyyyy too close. You need at least 3 inches. 

Their 25hz tune is probably for a flat response and sacrifices output


I AM The Future of personal transportation, NOW!!
Pretty sure everyone on this site hates you (@JohnKuthe) more then me and that's very hard to accomplish.

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Ok first off....bookmark this page, this should be the only box calculator you ever need:  https://www.the12volt.com/caraudio/boxcalcs.asp

I swear by that box calc, its dead on with Winisd and Bass Box Pro. 

 

Moving on....

With the dimensions you have chosen 26 wide 18 high 18 deep and 3/4 thick wood we have 3.86003 cubic feet BEFORE sub, port and bracing displacements are subtracted. This number is often referred to as GROSS volume. After you subtract sub, port and bracing displacements the resulting final volume is often referred to as NET volume. It's important to pay attention to this when reviewing a manufacturer's suggested design. 

Using that link you provided I see that the driver displacement is .109 cubic feet. 

 

As far as tuning, 25hz is too low for a car because cabin gain boosts the low end. The lowest I would tune for daily is about 30hz. So lets calculate the port length needed for 30hz.

 

This is where it gets a little tricky. We need to know how long of a port to use, which will also determine the volume of the box. Since both of those values dependent on one another it might seem like a revolving wheel and can't be done. A  program like Bass Box Pro or Winisd can figure this out real quick, but when you don't have those programs or understand how to use them, this is where that link at the beginning becomes real handy.

 

We know there is 3.75103 cf left after the sub displacement is subtracted. Now we will estimate the port displacement around .05 and subtract that from 3.75103 and plug that number into the round port calculator at the top of that link. 4 inch port, 3.7cf and we want a tune of 30hz. This calculates 7.24 or round up a tenth to 7.25 inches. If you are using a flared port the manufacturer typically recommends adding 1 inch to the port length to compensate for the flares. So now we are up to 8.25 inches of port length. 

Now scroll to the bottom of that page to the volume calculator of a cylinder. This is what we use to calculate port volume. Keep in mind we want to measure the OUTSIDE diameter of the port, not the inner. A typical 4 inch aeroport is about 4.25-4.5 in outer diameter. Lets go with 4.25 for that number and 8.25 inches for height of the cylinder. Put in a 0 for thickness so the clac doesn't treat it as an enclosure, the result is .06568 cubic feet. Keep in mind the flares are bigger than a straight tube that we calculated from but the difference isn't important enough to make a difference and for the sake of simple explanation we will ignore that. 

Our original estimate of .05 wasn't too far off. Go back to our volume after sub displacement of 3.75103 and subtract our port volume to get a final volume of 3.68545. 

We now have all of the numbers we need to get final volume and tune of our box. Go back up to the top of the page and plug all the numbers into the round port calculator. 

4 inch port, 3.68545 cf, 30hz gets 7.284inches (+1 for the flares) is 8.284. It's easier to round down to an easier fraction so 8.25inches.

So with those dimensions and a 4 inch aero port 8.25 inches long, you'll be tuned to 30.05hz. 

When you are a beginner designing boxes, its easiest to use whole or half numbers for dimensions. The ports can get a little more specific, but I usually only bother within .25 inch.  

Edited by THATpurpleKUSH
  • Thanks 1

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Thank you THATpurpleKUSH! Pm sent your way.

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Here are the models of the JL suggested vs your design. 

2.pdf


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Thanks THATpurpleKUSH but I don’t understand any of that.. 

 

 

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Basically everything looks good but you might want to use more port area if you plan on giving it more than 350w. 


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UPDATE: NEW DIMENSIONS (previous enclosure size does not fit through trunk opening)

31 x 15.5 x 18 (W x H x D)

My goal is to tune at least 3.5cubes at 30hz

Port area seems very low on a single 4" aero 7-8inches long. Equals to about 12.56 of port area. That's 3.33 per cube.

Single 6" aero 19inches long gives me about 28.26 of port area. 8.10 per cube. Sounds better but this forces me to vent out the side. My plan was driver and port on baffle.

If I go with two 4" areo's 16inches long I'll have 25.12 of port area. 7.05 per cube. With this design the inside flare is almost 1in from the back wall.

Tuning higher will correct these issues but I don't want to loose 27hz, 28hz, 29hz,30hz output.

 

Anyone have any suggestions or experience?

 

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Aeroports don't need as much area as slot ports, 7-11sq inchs per cubic foot is all you need. You need to have clearance at the end of the port that is equal to or larger than the port's diameter. 


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11 minutes ago, THATpurpleKUSH said:

Aeroports don't need as much area as slot ports, 7-11sq inchs per cubic foot is all you need. You need to have clearance at the end of the port that is equal to or larger than the port's diameter. 

The single 4" aero 8inches long equals terrible port area. Are you saying it'll be ok bc of the low power going to the driver?

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15 minutes ago, Wiz Khalifla_85 said:

The single 4" aero 8inches long equals terrible port area. Are you saying it'll be ok bc of the low power going to the driver?

Yep, usually you use a 6 inch or 2 4inch aeros on a 15 under ~1500w.  That's why I said you were at the limit of the port with 400w. 


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15 minutes ago, THATpurpleKUSH said:

Yep, usually you use a 6 inch or 2 4inch aeros on a 15 under ~1500w.  That's why I said you were at the limit of the port with 400w. 

Alrighty then. I'll try the 4"aero and see how it goes.

 

 

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Final Design for a single 15 with lot's of help from THATpurpleKUSH. Thank's bro. First time messing with aeroports and torres.. 

 

 

Screenshot (13).png

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Looks good, so you're letting the port stick out of the box by 5.75 inches?


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15 minutes ago, THATpurpleKUSH said:

Looks good, so you're letting the port stick out of the box by 5.75 inches?

Yea, I decided to go with the 6" aero bc if I ever decide to get a beefier 15 I can always toss it in this enclosure. I also didn't want the port firing to the side.. I think this enclosure's going to sound great..

 

How should I go about securing the aero sticking out of the enclosure?

Edited by Wiz Khalifla_85
add text.

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2 part epoxy. You can get a 90 degree pvc elbow to put the port on the same face as the sub.


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