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regal8r
04-14-2006, 09:03 PM
im gonna be building a new box but i need help with port length...volume is 5.2675 after driver displacement only. i would like to tune to 33hz, port area is 3x14.5 with 2 ports, one on each side of the box. OD's of the box is 36x25.5x16...this will also be for 2 05 12" type r's and hifonics bx2005d in a 96 monte carlo...thx.

hofulstrof
04-14-2006, 09:09 PM
download winisd

35" vent length based on 5.2 cf but at that lenght each port will displace 1.0cf....

regal8r
04-14-2006, 09:11 PM
i have winisd but dont know how to use it lol...im looking for about 5cf after all displacements...do u have any suggestions?

hofulstrof
04-14-2006, 09:22 PM
either make the box larger,raise the tuneing or decreas the port area.
i would shoot for around 28 sq" of port per sub

regal8r
04-14-2006, 09:29 PM
ok so that would be about 2"x14.5" ports...would that be enough port area for type r's??

hofulstrof
04-14-2006, 09:50 PM
yes

regal8r
04-14-2006, 10:11 PM
what would my volume come out to be after port displacement with 2" ports then?

hofulstrof
04-14-2006, 10:18 PM
length will be 23"

to get a rough estimate of how much a slot port will displace use this formula

( (width+wood thickness)x hight x length)) /1728= displacemnt

(2+.75)x14.5x23"/1728
2.75x14.5x23/1728
=.5 cf displacement

regal8r
04-14-2006, 10:30 PM
length will be 23"

to get a rough estimate of how much a slot port will displace use this formula

( (width+wood thickness)x hight x length)) /1728= displacemnt

(2+.75)x14.5x23"/1728
2.75x14.5x23/1728
=.5 cf displacement
what length, port length?? u said at the top that i would need 35" long for each port...

hofulstrof
04-14-2006, 10:31 PM
yeah but you are now going with less port area so then the length will also be reduced

5.2cf@33hz with 2 ports with 29sq" of port (14.5x2) will have a vent length of 23 "



refined formula

( (width+wood thickness)x hight x port length)) /1728= displacemnt

regal8r
04-14-2006, 10:34 PM
so each port should be 35" long then, correct?

hofulstrof
04-14-2006, 10:36 PM
sorry i edited my post... look again

regal8r
04-14-2006, 11:03 PM
i dont see an edit :confused:

hofulstrof
04-14-2006, 11:05 PM
post # 10
the part about your port length being shorter because you are going with less area?

regal8r
04-14-2006, 11:07 PM
alright, i see it now....so each port will be 23" to get me a tuning of 33hz then???

hofulstrof
04-14-2006, 11:12 PM
yes but you have to remember each port will displace volume inside the box.

so if you box is 5.2 cf after brace and sub displacemnt. and each port displaces .5cf (useing my simple formula.) then you are really going to have a box that is 4.2 cf. and now you port length is going to change ..... confuseing isnt it.

this is why sketch up is such a popular program.it saves on alot of time calcualting displacemnts and such.

regal8r
04-14-2006, 11:34 PM
yes but you have to remember each port will displace volume inside the box.

so if you box is 5.2 cf after brace and sub displacemnt. and each port displaces .5cf (useing my simple formula.) then you are really going to have a box that is 4.2 cf. and now you port length is going to change ..... confuseing isnt it.

this is why sketch up is such a popular program.it saves on alot of time calcualting displacemnts and such.
lol yea, i have it, i just dont know how to use it

hofulstrof
04-14-2006, 11:36 PM
i should make a turial on how to use it ....

regal8r
04-14-2006, 11:38 PM
i should make a turial on how to use it ....
that would be highly valuable to alot of members on here...

hofulstrof
04-14-2006, 11:39 PM
ok ill make one later tomorrow or sunday.
sent you a pm to ragal