Port formula by hand!? got problems...

[ngsm13 5,000+ posts]

Hey, so using the formula @ JL:

http://www.jlaudio.com/tutorials/ports/index.html

I solved for Lv, and got some whacky number (like in the millions). Maybe i'm a retard...but...i need help.

Fb= 32hz

Av=70 (14x5)

Vb=7.25 cubic feet

So, what am i doing wrong, any help would be appreciated! I want to see the exact length i'd need.

Also, the current design i have is:

Av= 70

Vb= 7.25 cunic feet

Lv=18

What's the exact tuning (by hand, i don't trust winisd or ****).

Thanks for any help provided...i'm going to continue to attempt figuring this out. peace

NG

Click to read more...

 

[Randy Savage 5,000+ posts]

Convert box volume into cubic inches...//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[ngsm13 5,000+ posts]

Convert box volume into cubic inches...//content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

OOOOOHHHHHHH! fer shizzle...so... 7.25 cubic feet would be...

7.25*1728=12528 correct?

peace

NG

 

[Randy Savage 5,000+ posts]

Yup

10chars

 

[ngsm13 5,000+ posts]

PHUCK!!!

It's still ****ed up, i'm a retard....

Any help?!?!

peace

NG

 

[Randy Savage 5,000+ posts]

I got 30.5

 

[supa_c 5,000+ posts]

Ahhh, deletion !

yeah, uncalled for, but so are someother posts //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[ngsm13 5,000+ posts]

WOW! 30.5 that is extremely off what i designed in WinISD.

Any help on this?

Also, the current design i have is:

Av= 70

Vb= 7.25 cunic feet

Lv=18

What's the exact tuning (by hand, i don't trust winisd or ****).

Thanks for any help provided...i'm going to continue to attempt figuring this out. peace

Thanx, peace

NG

 

[OLD_SCHOOL 10+ year member]

I got 30.5

thats is way wrong

av= 70

vb = 7.25

fb= 32

(70 * 1.84 x 10^8) / (7.25 * 1728 (32/.159)^2 ) - (.823 * sqrt 70 ) = 18.49643822

Lv= 18.49643822 by hand

 

[ngsm13 5,000+ posts]

Ok OLDSCHOOL, i realllllly appreciate it! I got flustered....and rushed...and went ahead with an 18" long port. So tuning should only be slightly higher. Thanks you a lot oldschool! peace

NG

 

[OLD_SCHOOL 10+ year member]

yeah man your only talking like a 1/2 inch if your using winisd pri with the update it's pretty close

where alot people go wrong is when they try to figure out a second port wall on a L shape length and displacment

 

[ngsm13 5,000+ posts]

yeah man your only talking like a 1/2 inch if your using winisd pri with the update it's pretty close
where alot people go wrong is when they try to figure out a second port wall on a L shape length and displacment

true! that's why i did it this way...i didn't want to do an L-shape port...that is the largest port area i could do and still keep it straight! peace

NG