View Full Version : Vented Formulas

billy18bm

05-01-2007, 11:25 PM

First of all i have read all the stickies and i would just like to

know how to bulid a vented box

i understand cu ft. and volume but how do you calculate the TUNED FREQUENCY

of your port of just a basic rectangle box w/ a vented port?...

i cant seem to find it anywhere on the forums..

i have two type r's and they are recomended for 1.7ft^3 in a vented enclosure

and i would like to tune it at around 33 hertz

any help would be appriciated

thank you

thehardknoxlife

05-02-2007, 12:13 AM

Lv=[(14630000xR^2)/(Fb^2xVb)]-1.463xR

Lv= port length

Fb=Tune frequency

Vb= cubic ft x 1728.

Slot

R= SQrt of Port area / 3.14

Round

R= inside radius of vent tube

Immacomputer

05-02-2007, 12:25 AM

Download winisd and plug the enclosure specs in there. It will tell you what you need to know and it's accurate.

Beginer

05-02-2007, 02:36 AM

Lv=[(14630000xR^2)/(Fb^2xVb)]-1.463xR

Lv= port length

Fb=Tune frequency

Vb= cubic ft x 1728.

Slot

R= SQrt of Port area / 3.14

Round

R= inside radius of vent tube

Hey,

are you sure that Lv formula is good?

Because I use another formula which is a little diferent...

Here it is: http://i162.photobucket.com/albums/t246/Kickerlivenloud/PortLengthsolved--Thisoneisright.jpg

And to find what is tuning freq I use this formula:

Fb=SQRT((Av*1.84*POWER(10,8)*POWER(0.159,2))/(Vb*1728*(Lv+0.823*SQRT(Av))))

Just copy it to Excel and change Av, Vb, Lv and you will get tuning freq. :)

thehardknoxlife

05-02-2007, 02:43 AM

Hey,

are you sure that Lv formula is good?

Because I use another formula which is a little diferent...

Here it is: http://i162.photobucket.com/albums/t246/Kickerlivenloud/PortLengthsolved--Thisoneisright.jpg

And to find what is tuning freq I use this formula:

Fb=SQRT((Av*1.84*POWER(10,8)*POWER(0.159,2))/(Vb*1728*(Lv+0.823*SQRT(Av))))

Just copy it to Excel and change Av, Vb, Lv and you will get tuning freq. :)

Yep, you can use either one. I just find that one alot easier to remember.(I'm not a box builder BTW, I just read alot.)

Trixter

05-02-2007, 02:20 PM

...I just read alot

lol

yes, use the one in my sig....much easier. just remember that the Vb is in cu INCHES.

SHiZNiLTi

05-02-2007, 04:22 PM

http://www.carstereo.com/help2/Articles.cfm?id=31