port help??

[kyleorsini 10+ year member]

i need to find out the sizing of 2 tube ports for my box, i have calculated it and

according to someone he thinks the ports might be a bit too small, and i may experiance port noise so heres what i got

box- 21W 15D 15H which = 2.06 cubes.

i want it at 35hz.

ports- 2 - 2.5" diameter at 9 inches in length

so with those numbers would the ports be enough for the box

the sub is a 12" type R and the displacement is .071

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[mazdakid 5,000+ posts]

no you need more port area

 

[Bake 10+ year member]

How much power are you going to be sending to the sub? You may be okay up to about 350-400 watts. Over that port noise may be an issue.

 

[kyleorsini 10+ year member]

okay and how much more??

 

[skmfkr 5,000+ posts]

2 3" would probly work

 

[kyleorsini 10+ year member]

well with my alpine mrpm500 its 500 rms soo about that

okay if its 3 inches then how long would they be? and

how would i get 35hz from a 2cube box would that be acheaved

by the port?

 

[skmfkr 5,000+ posts]

http://www.carstereo.com/help/Articles.cfm?id=31

 

[Bake 10+ year member]

Two three inch ports would need to be around 13.25" which may be too long for the box you are building. You don't want the port tubes to be too close to a wall.

 

[kyleorsini 10+ year member]

yeah i just calculated the port and got the length well

with doing 2-3 inch tubes at 13.25 inches and if i changed the

depth to 17 and the width down to 20 would that work?

or what other suggestions is there?

 

[Bake 10+ year member]

I would keep the end of the ports at least 3" from a wall if you use 3" ports. You can put an elbow in if you can't work it out any other way. Just measure down the center of the elbow and use the largest radius(less bend) you can.

 

[kyleorsini 10+ year member]

alright, so if i made it 17 it would be good i wouldnt

need a bend in the tube, also how do i secure the tube inside the box?

 

[Bake 10+ year member]

If you are able to fit a straight port with no bends a good tight fit through the baffle may be enough to hold it in place. If you need more support you could glue it to a small block inside the box. Remember to take port displacement and any bracing that you use into account when doing calculations for your box.

 

[skmfkr 5,000+ posts]

the 4 screws for the end of the port should be enough, ive got 4 4" aeros that are 15" long with no support only the 4 screws

 

[Undisputed King 10+ year member]

I dont know why everyone uses those plastic ports, I personally like slotted ports, they are free. But I think 2 4" port tubes will bring you to 25 sq inches of port area, which is right around what you need for 1.7 cu ft, which will be the net cu ft you will probably be left with.