View Full Version : port help??

01-14-2009, 06:42 PM
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

01-14-2009, 06:57 PM
no you need more port area

01-14-2009, 07:01 PM
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.

01-14-2009, 07:02 PM
okay and how much more??

01-14-2009, 07:02 PM
2 3" would probly work

01-14-2009, 07:06 PM
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?

01-14-2009, 07:07 PM

01-14-2009, 07:10 PM
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.

01-14-2009, 07:16 PM
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?

01-14-2009, 07:24 PM
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.

01-14-2009, 07:32 PM
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?

01-14-2009, 07:44 PM
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.

01-14-2009, 09:23 PM
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
01-16-2009, 01:35 AM
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.