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#### elvisjer

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Hello everyone! Im working on a box for my Aurasound NS10, going off of thier recommended 1.6cu.ft. ported design. I'm using the calculator software at, "http://www.carstereo.com/help/Articles.cfm?id=31" and am running into a little bit of trouble. Before, i didn't quite understand the whole port-noise idea so I used the lower calculator only and made a 2.25"x4" port on the box. Well i finished it and now i DO understand port noise!

The results of the port noise calculations are thus:

Minimum Diameter = 5.81 inches
Minimum Area = 26.51 inches
Length of a side for a square vent = 5.15 inches

Since I have more of the 2.25" tubing, i was thinking the easiest way would be to take the tube that's in there out, and add two more round ports. When i enter "three round ports x 2.25" each" into the port length calculator, do i enter the "Desired Port Diameter" as 5.81" or 2.25"?
Is the resulting number for EACH of the three ports, or do i take that number and divide it by 3 and do that length for each port?

This is all assuming that the 3x 2.25" ports will indeed NOT have port noise since they equal larger than 5.81" total...right?

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#### el_chupo_

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the actual answer to your question is enter 2.25 for the desired port diameter.

#### elvisjer

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yes, i've entered 2.25, but then I'm wondering about length of the port, do i divide the final number by the amount of ports, or is each port that length? Thanks!

#### Oliver

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each port is that length

quote>

Now let's decide that we don't want just a single port because it looks boring. Let's put a 2" port in each corner of the box for a total of 4 ports and see what the two methods give us:

Method 1:
Each 2" port has a cross-sectional area of 3.142 square inches so we multiply that by 4 to get 12.57 square inches. Plugging in 12.57 for Av in the port formula yields Lv = 18.844 inches for each port.

Method 2:
We want to use 4 ports so we divide 2.5 cubic feet by 4 and get .625 cubic feet. Vb now becomes .625 cubic feet. We are using 2 inch diameter ports so Av is 3.142 square inches. Plugging these numbers into the equation leads to Lv = 20.302 inches for each port.

Notice that Method 1 produces the same port length as did our single 4" diamter port as it should (after all, we have the same total port cross-sectional area which this school of thought proclaims is correct!). But the first method is incorrect because it neglects the frictional losses encountered by using many smaller ports--there is a higher port wall surface area to cross-sectional area ratio which raises the total amount of frictional losses in the ports and thus shifts the tuning!
quote>

This is one or two ways to do it...

#### TREETOP

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Why not do a single slot port and eliminate so much of that turbulence?

#### elvisjer

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when you say slot port, does that mean just cutting a slot in it, or does this mean making a L shape inside with slot port outside? I'm up for whatever is easier, i'd like to salvage this box if I can and it's tough to work on now that its complete.

#### TREETOP

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It's a square or rectangular port made out of wood instead if tubing, yeah sometimes it'll look like an L if the required depth is deeper than what you have room for. A slot port allows you to use whatever opening area you want, not limited to PVC sizes. Using a single larger port also helps keep huffing and port noise down.

Use this program to help visualize:
RE Enclosure Calculator

Here's one I built recently as an example:

#### Oliver

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Hello everyone! Im working on a box for my Aurasound NS10, going off of thier recommended 1.6cu.ft. ported design.!
Go up to the next size
use a slightly larger tube and make it 4 inches longer

#### elvisjer

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Go up to the next size
use a slightly larger tube and make it 4 inches longer
YOu mean keep only one port? I need a port area of 5.81" though.

#### bballer123

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I have always had a good amount of luck with WINISD if you use windows...

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