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View Full Version : 67.5in^3 = port noise?



rollerdj
05-18-2009, 05:41 PM
using a 18" RL-p based sub, running 850rms. 13.37ft^3 box with 67.5in^3 of port, tuned to 20hz. think i'll get any port noise with this? or should i go a little bigger.

Xprime4
05-18-2009, 05:42 PM
Wow that'll be a low end monster. I would say at least 2x bigger with the box size

rollerdj
05-18-2009, 05:44 PM
HT sub FTW!

snb778
05-18-2009, 05:45 PM
the minimum port you want for that box is 156 sq. in, unless you're using a round port, thenyou would only need like 75sq. in.

rollerdj
05-18-2009, 05:46 PM
i could do 22.25 x 4 and end up with 90?

rollerdj
05-18-2009, 05:54 PM
24"x 6.5" should get me close. i'll have to fold the port back and forth i think. it'll be sub side, port back most likely. unless someone can come up with a better way of doing it. sub would end up being about 3' away from the side wall. but the port will be more like a foot.

dappa5
05-18-2009, 05:57 PM
using a 18" RL-p based sub, running 850rms. 13.37ft^3 box with 67.5in^3 of port, tuned to 20hz. think i'll get any port noise with this? or should i go a little bigger.
how did you get 13.37 ? is this before sub and port displacements?
what are your max dims?

01 S 10
05-18-2009, 06:02 PM
you need a wayyy bigger port, my port that size was in my 4.5cf box.

rollerdj
05-18-2009, 06:03 PM
actully i was wrong, acording to RF's website it is 13.21. 24"x51"x22". driver displacement is .2ft^3. not including port displacement.

dappa5
05-18-2009, 06:06 PM
actully i was wrong, acording to RF's website it is 13.21. 24"x51"x22". driver displacement is .2ft^3. not including port displacement.
Re? dude send me your max dims I'll fix you up
:D:D:D:D

flaboy
05-18-2009, 06:07 PM
if you are using .75" mdf..then it is only 12.62 cubes.....and with the sub in it (no port) its 12.42 cubes.

rollerdj
05-18-2009, 06:19 PM
actully i was wrong, acording to RF's website it is 13.21. 24"x51"x22". driver displacement is .2ft^3. not including port displacement.
thats the max size.
http://i211.photobucket.com/albums/bb191/rollerdj-77/uploadtoday067.jpg
basicly, the plan is to replace that tv stand as it doesn't like the new tv, and replace it with the box for the 18. so i don't wanna go to much bigger than that.

Re? dude send me your max dims I'll fix you up
:D:D:D:D

http://www.soundsplinter.com/rlp18_subwoofer_information.html

there is the link to the spec's. this sub should be really close to that.

Ellsworthz
05-18-2009, 06:21 PM
cod4 ftw

dappa5
05-18-2009, 06:22 PM
cod 4 rocks cod 5 rocks more gamertag=username here

flaboy
05-18-2009, 06:22 PM
we can tell you dont know the math behind designing a box....idk how the **** you came up with 13 cubes....when the box is smaller than that itself.

SSS 18734
05-18-2009, 06:23 PM
Unless you plan on running that sub at full output all the time, that port should do, especially in home theater. Going slightly bigger wouldn't hurt - Go as big as you can before you have to start bending the port inside the box.

davidt487
05-18-2009, 06:28 PM
im building mine as we speak and its 24"X52.5"X18" and im going 6 cuft tuned to 20 90sqin of port if i remember correctly

dappa5
05-18-2009, 06:29 PM
dude try this http://www.decware.com/newsite/hwk15.htm

rollerdj
05-18-2009, 06:29 PM
we can tell you dont know the math behind designing a box....idk how the **** you came up with 13 cubes....when the box is smaller than that itself.


go to
http://www.rockfordfosgate.com/rftech/box_wizard.asp

rectangle box
standard measurement
3/4" mdf
"gross" measuring method.


thats what i used. if you don't have anything constuctive to say in my thread, get the **** and post elsewere. kthxbye.

rollerdj
05-18-2009, 06:30 PM
Unless you plan on running that sub at full output all the time, that port should do, especially in home theater. Going slightly bigger wouldn't hurt - Go as big as you can before you have to start bending the port inside the box.

this sub will most likely never see full tilt. no need in this living room.

flaboy
05-18-2009, 06:36 PM
go to
http://www.rockfordfosgate.com/rftech/box_wizard.asp

rectangle box
standard measurement
3/4" mdf
"gross" measuring method.


thats what i used. if you don't have anything constuctive to say in my thread, get the **** and post elsewere. kthxbye.

ok constructive learn the formulas needed to calculate volume of a box...obviously if you multiply all 3 dimensions up you get the cubic inches...divide that by 1728 and thats how many cubic feet a solid sealed box is...then you have to calculate how much airspace the port takes up. that constructive enough *******

davidt487
05-18-2009, 06:48 PM
to go by there specs from their website you will need a much bigger box. 12 cuft tuned the 18hz
that is 12 cuft +port and sub and brace disp.

rollerdj
05-18-2009, 06:52 PM
yea, once you guys started to say more port i was getting worried. i wasnt figuring on that much port. i'll have to take a tape measure to the area and see what i can come up with. maybe a full entertainment center with the base of the center being the box for the sub?

rollerdj
05-19-2009, 08:02 PM
http://i211.photobucket.com/albums/bb191/rollerdj-77/Entertainment.jpg

ok, new plan. full out entertainment center. new size will be 22"x22"x98" :D that should give me more than enough room. anyone wanna come up with a plan for me?