How To Tune The Port! Not So Hard

[jellyfish420 10+ year member]

(45 * 1.84x10^8)/(4 * 1728 x (38/.159)^2) enter - (.823 * sqrt 45) your answer will be 15.452"

what is the diff between * and x ? they are both times, right?i did it on my calculator a couple times, and by hand and keep coming up with 204.2" what am i doing wrong???

 

[OLD_SCHOOL 10+ year member]

something ive always wondered is how is this forumla derived? anyone have a proof?

solve for lv

 

[jellyfish420 10+ year member]

ok, now i'm really confused i did the formula above to solve for tuning. first i used 15" and i got like 200Hz. but when i used 204" i got 38Hz. some one, what the hell am i doing?

 

[OLD_SCHOOL 10+ year member]

jelly i don't bro, make sure you have all the () in the right places and such

 

[jellyfish420 10+ year member]

i typed it in exactly as you did.

(45x1.84x10^8)/(3x1728(38/.159)^2)enter-(.823xsqrt45)

8.28^10/394799572.8=209.727

.823xsqrt45=5.52

209.727-5.52=204.2

what the hell???

 

[Threshld1 10+ year member]

solve for lv

thats not what im asking, i know what the formula and how to manipulate it, im asking the calculus/physics behind it, where did it come from the same way that ohms law comes from the graph of voltage vs current or E \ I = R or esentialy the slope know what i mean? like why is it .159 times the square of.....

 

[jellyfish420 10+ year member]

Using a scientific calculator ...
38/0.159 = 238.9937107

^2 =57117.99375

*4*1728 = 394799572.8

1/X = 2.532930806*10^-9

*45*1.84*10^8 = 20.97266707

- 0.823*Sqrt(45 = 15.45181523

I think you used 10^9 instead of 10^8 //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

1/X = 2.532930806*10^-9

where did this line come from? please help i really want to learn how to do this on my own. and i did use 10^8, but now that you said that, if i type it in my calculator as posted using 10^7...it comes out right?

 

[BiaBia 10+ year member]

10000000, thats how its written out.

 

[req 5,000+ posts]

i am still looking forward to that calculator. ill get my brother to write a program to figure out that arithmatic and see if he cant come up with anything. (he is a CS major rochester institute of tech, and im sure he can program somthing simple like this)

 

[Scarenius 10+ year member]

I try, but noone here is willing to answer my questions, so there's no point. The calculators already exist, and mine is just going to be clone of them.

Here's the latest version and it's results. Something is by far off. I need an accurate equasion, and as far as PHP is concerned, none of the ones above here have worked.

Box size: 6192 square inches or 3.5833333333333 cubic feet

Port: 45 inches^2

Frequency: 38 HZ

You port Length!

Calculation 1 : 1724.038737134 inches

Calculation 2 : 69.049928777938 inches

Calculation 3 : -5.5202977266075 inches

 

[req 5,000+ posts]

i understand that, but i do only have limited knowledge of programming, and port calculations. what question was it you needed to awnser?

 

[Scarenius 10+ year member]

None really, I just need more ways of doing this equation, because every answer seems different.

My 3 port equaions are as follows, and all of them are off.

$port1 = ($x*(1.84*10^8))/($y*(sqrt($z)*.159^2))-.823*sqrt($x);
$port2 = ((14630000*($y/2)*($y/2))/(($z*$z*($x/144)*1728)-(1463*($y/2))));
$port3 = ($y * 1.84*10^8)/($x * (38/.159)^2);  $port3 = $port3 - (.823 * sqrt($y));

$x = the size of the box in cubic inches, $y is the size of the port in square inches, and $y is the frequency.

 

[req 5,000+ posts]

None really, I just need more ways of doing this equation, because every answer seems different.
My 3 port equaions are as follows, and all of them are off.

$port1 = ($x*(1.84*10^8))/($y*(sqrt($z)*.159^2))-.823*sqrt($x);
$port2 = ((14630000*($y/2)*($y/2))/(($z*$z*($x/144)*1728)-(1463*($y/2))));
$port3 = ($y * 1.84*10^8)/($x * (38/.159)^2);  $port3 = $port3 - (.823 * sqrt($y));

$x = the size of the box in cubic inches, $y is the size of the port in square inches, and $y is the frequency.

did you try it by hand? maybe the computer is calculating somthing first that needs to go second?

 

[Scarenius 10+ year member]

Probably. My math skills are not up to par with this, and haven't been for the past few days.

I'm going to try basically doing it one step at a time, on paper, if it works out, I'll try to punch in the step by step equasion.

 

[req 5,000+ posts]

alright, from what ive heard - thats usually the problem. with peoples math (mine too)

order of operations;

http://www.google.com/search?hl=en&q=order+of+operations&btnG=Google+Search

http://www.mathgoodies.com/lessons/vol7/operations_exponents.html

Parentheses

(Innermost, first)

Exponents

(Powers or roots)

Multiply or Divide

(from LEFT-to-RIGHT)

Add or Subtract

(from LEFT-to-RIGHT)

maybe thatl help