Car Audio Classifieds! banner
1 - 16 of 16 Posts

·
Registered
Joined
·
258 Posts
Discussion Starter · #1 ·
Does anyone know how to actually tune a box to the hz level you want. I have always had my boxes built for me and I want to try to do my own this time. I can figure out volume and things like that but I am completely lost with the tuning. Sorry about such a newb question.
 
  • Like
Reactions: quaddropper

·
me neither
Joined
·
894 Posts
id like to know this as well. there are calcs out there for this but I like to know the math behind it.


Tim
 

·
me neither
Joined
·
894 Posts

Okay if you follow the above link to the JL site you will see this formula, and it goes into detail about ports.

I read about the cross-sectional length of the port, and I understand
some of the other terms, but how do use this formula??


Im just having a really hard time wrapping my mind around this formula. Can anybody help me on this?? I know I can find port calcs and other software, but I dont just want to depend on the computer Id like to be able to do it MYSELF.

Thanks,

Tim
 

·
Registered
Joined
·
6,135 Posts
Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)


It is very easy, you just need to know what the letters stand for.

Dv = port diameter (cm)
Fb = tuning frequency (Hz)
Vb = net volume (litres)
Lv = length of each port (cm)
Np = number of ports
k = end correction (normally 0.732)

Find your port diameter for a circular aero port including end correction factor. If you are going slot ported, just follow this formula to convert the equivalent cross section of slot port to a round one to throw in the above equation:

Dv' = 2*((W*H)/pi)^0.5


where, Dv' = diameter of equivalent round port
W = width of slot
H = height of slot
 

·
mega fatty
Joined
·
6,008 Posts
Port Length


  • Lv = Av*1.84*10^8/[Vb*1728*(Fb/0.159)^2]-0.823* SQRT (Av)
  • Fb = 0.159*SQRT[(Av*(1.84*10^8)]/(Vb*1728*[Lv+(.823*SQRT(Av))])

  • Vb is true net volume (all displacements taken into account)
  • Fb is the enclosures resonant frequency (tuning)
  • Av is the cross-sectional area of the port (port area)
    1. (area of a circle is pi*r^2)
    2. (area of a rectangle is h*w)
  • Lv is the length of the port
this has always helped me but i just use bbp6 or winisd
 

·
Idk what Im talking about
Joined
·
8,346 Posts
  • Like
Reactions: cotyballs

·
me neither
Joined
·
894 Posts
Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)


It is very easy, you just need to know what the letters stand for.

Dv = port diameter (cm)
Fb = tuning frequency (Hz)
Vb = net volume (litres)
Lv = length of each port (cm)
Np = number of ports
k = end correction (normally 0.732)
Thanks for trying to help me but I just aint clikcing. I wrote the equation out on paper and did the numbers like we used to in algebra the ones in the () first.

And I came up with some screwed up number i cant make heads or tails of. I converted to metric when I needed to.

(23562.5*7.62/(2304*27.69))-(.732*762)
(34212750/(63797.76))-(557.8)
536.26-557.8
-21.54

Port diameter = 3 inches
Tuning freq. = 48hz
Vb = 27.69.

Where am I missing the boat?? I hate to be a noob or something but I just aint getting it.

Tim
 

·
Idk what Im talking about
Joined
·
8,346 Posts
Thanks for trying to help me but I just aint clikcing. I wrote the equation out on paper and did the numbers like we used to in algebra the ones in the () first.

And I came up with some screwed up number i cant make heads or tails of. I converted to metric when I needed to.

(23562.5*7.62/(2304*27.69))-(.732*762)
(34212750/(63797.76))-(557.8)
536.26-557.8
-21.54

Port diameter = 3 inches
Tuning freq. = 48hz
Vb = 27.69.

Where am I missing the boat?? I hate to be a noob or something but I just aint getting it.

Tim
Let me know the net cubic feet, port area, and effective port length and I can tell you the tuning in seconds.
 

·
Registered
Joined
·
6,135 Posts
Thanks for trying to help me but I just aint clikcing. I wrote the equation out on paper and did the numbers like we used to in algebra the ones in the () first.

And I came up with some screwed up number i cant make heads or tails of. I converted to metric when I needed to.

(23562.5*7.62/(2304*27.69))-(.732*762)
(34212750/(63797.76))-(557.8)
536.26-557.8
-21.54

Port diameter = 3 inches
Tuning freq. = 48hz
Vb = 27.69.

Where am I missing the boat?? I hate to be a noob or something but I just aint getting it.

Tim

Did you throw in port diameter? VERY important. If you are going slotted instead of round then you have to convert it.
 

·
Idk what Im talking about
Joined
·
8,346 Posts
Did you throw in port diameter? VERY important. If you are going slotted instead of round then you have to convert it.
This is why an equation done by hand is better imo, you just need to find port area without worrying about calculators being off etc.
 

·
Registered
Joined
·
6,135 Posts
Yeah...It seems long and tough at first, but it is good to learn, why spoon feel people you know, it helps alot and calculators are just eh...Every one of them give you different results.


We need to make an in depth tutorial on it all like total displacement, port area style, port area hand calculation, end correction(flare), and then how you have to subtract the ports actual displacement aswell and then redo the formula and what parts of the port count as displacement(the inside of the port for instance is NOT usable box volume, and takes up room aswell) etc...
 

·
me neither
Joined
·
894 Posts
Did you throw in port diameter? VERY important. If you are going slotted instead of round then you have to convert it.
I thought I did:dontknow: lol



This is why an equation done by hand is better imo, you just need to find port area without worrying about calculators being off etc.
I actually prefer to LEARN how to do it so I dont have to depend on a calculator


Yeah...It seems long and tough at first, but it is good to learn, why spoon feel people you know, it helps alot and calculators are just eh...Every one of them give you different results.


We need to make an in depth tutorial on it all like total displacement, port area style, port area hand calculation, end correction(flare), and then how you have to subtract the ports actual displacement aswell and then redo the formula and what parts of the port count as displacement(the inside of the port for instance is NOT usable box volume, and takes up room aswell) etc...

That would be vry helpful to people like me who are really still learning and relearning everything I already learned before.

Tim
 
1 - 16 of 16 Posts
Top