How To Tune The Port! Not So Hard

[BiaBia 10+ year member]

When you do the exponent of 10^8, make sure it comes out like this

10000000

not

100000000

 

[req 5,000+ posts]

yea.

x2

 

[tRiGgEr 5,000+ posts]

My calculator can't go that high...

I have 2.04 cubic feet or 3525.12 cubic inches. 13.5 x 2.75 port and want 32hz tunning. Any one willing to plug it in to there scientific calculator for me? I need the port length.

Man my head hurts.

 

[req 5,000+ posts]

pencil + paper?

i dont have a scientific calculator =P

my brother is working on a working online-calculator, so just hold tight.

 

[jellyfish420 10+ year member]

try using the third one but instead of 10^8 use 10^7...i don't know why but thats how i have to type it into my calculator to get it to come out right

 

[req 5,000+ posts]

that may be the trick mr scarman

 

[sanosuke001 10+ year member]

I made a port calculator per my brother r3Q's specifications... just ask if you would like anything else added to it...

http://www.cis.rit.edu/~swr9025/sub.php

oh yeah. I saw someone else doing a php-kinda program and I was having the same problem as you were. I figured parens were giving me the trouble so I did something like:

$top = $portArea * 1.84 * pow( 10, 8 );

$bottom = $internalVolumeIN * pow( $frequency/0.159, 2 );

$minus = .823 * sqrt( $portArea );

$portL = ($top/$bottom)-$minus;

and it worked fine that way...

 

[Scarenius 10+ year member]

Req: Call me Ravo, it's easier to type.

Sano:

Looks good, you into the whole open source thing?

(would I seriously need a 43 inch port?)

A friend of mine gave me these equations for port size, box volume, and hertz, I'm trying those, too.

Av = (Fb / 0.159) ^ 2 / (1.84 * 10^8) * Vb(Lv + 0.823Av ^ 0.5)

Vb = Av(1.84 * 10 ^ 8 / (Fb / 0.159) ^ 2 / (Lv + 8.23Av ^ 0.5)

Lv = Av(1.84 * 10 ^ 8 / (Fb / 0.159) ^ 2 / Vb - 8.23Av ^ 0.5

 

[sanosuke001 10+ year member]

I don't know if you'd need a 43 inch port... I just used the equation that my brother gave me (it was at the top of this article...)

If you have a better equation, let me know and I'll see what I can do.

If you can tell me what Av, Vb, and Lv mean and what those three equations are used for, I'll let you know what they do. (I don't know anything about subs and cars... just programming for my brother req ^_^)

 

[BiaBia 10+ year member]

Everyone should have a scientific calculator on their computer.

Start > All programs > Accessories > Calculator

If its not already scientific, do this.

View > Scientific

All done.

 

[sanosuke001 10+ year member]

Two things about the one on the computer is that you have to type in every little section of the equation; you can't just type it in one long shot and then find the answer.... the computer one is really only made to do easy stuff...

I guess you could.... but it is very VERY difficult to keep track of parens and stuff.... and I really haven't tried because it was MUCH easier to write a PHP program to do it for me ^_^

 

[req 5,000+ posts]

hey there steve =)

thanks for that! thats a very nice looking calculator. lets see if it works...

WEW - fantastically sweet =D

steve. you are the MAN!

as for that sig, i should punch you in the eye. //content.invisioncic.com/y282845/emoticons/satan.gif.9c6a335ed7aeeed3ee273e573f1fcaac.gif just kiddin. i got 2 8's and a 200w amp for $100 steve. whatd ya think //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif eh eh??

thanks for the calculator man. email it to me?

so JMAC- does it work correctly?

**you might as well put a freaking banner on that page steve, cuz people are gonna link like crazy to it =)

 

[Scarenius 10+ year member]

More mathematical fun.

a = 0.159

b = 1.84 x 10^8

c = 0.823

ANYWAY, plugging this into the PHP equation gives you this.

$Lv = ($Av*$b)/abs(($Fv^2/$a^2))/($Vb)-$c*sqrt($Av);

# Av = cross section area of port

# Lv = Length of Port

# Vb = Net volume of enclosure

# Fb = Tuning Frequency

$a = 0.159;

$b = 1.84 * 10^8;

$c = 0.823;

I punched in the specs for my planned box. .813 cubes (.753 after sub displacement), a 2X10.5" port at 40hz. It told me -3.7437153658429 inches.

I'm either gettting this right, or not at all.

 

[jellyfish420 10+ year member]

look at this i found this...don't know if it will help anyone but here it is.http://www.the12volt.com/installbay/forum_posts.asp?TID=25814&PN=1

 

[req 5,000+ posts]

well i was told by a post form jmac that it was wrong, and it seems to have been fixed. so thats good news.

but we also have this alternate calculator that does feet AND inches. i think thats a large plus!

now all we need to do is put in box thickness, and some genaric volume calculator and throw it to .exe format, and it will be quite a versatile program!!