Beginner's guide to box building

[Lubega 10+ year member]

Thanks, man. I'm so glad I joined. I really appreciate good, solid information like this. //content.invisioncic.com/y282845/emoticons/veryhappy.gif.fec4fed33b4a1279cf10bdd45a039dae.gif

 

[baseballer1100 5,000+ posts]

What about a dado. That joint is sick....

 

[Dynasty 10+ year member]

Can someone explain how to tune a box?

Do I need to buy a special tool/instrument in order to tune a box?

 

[PV Audio 5,000+ posts]

To teach you box design, you're better off learning about the way boxes work, and then trying to design your own.

http://www.partsexpress.com/pe/pshowdetl.cfm?PartNumber=500-035&raid=29&rak=500-035

^^ Should help you extensively.

 

[PV Audio 5,000+ posts]

Thanks, man. I'm so glad I joined. I really appreciate good, solid information like this. //content.invisioncic.com/y282845/emoticons/veryhappy.gif.fec4fed33b4a1279cf10bdd45a039dae.gif

No problem, glad I could help //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[baseballer1100 5,000+ posts]

What about all the formulas for ports and stuff?

 

[PV Audio 5,000+ posts]

Okay, here are the main box formulas, courtesy of DIYsubwoofers.org :

Vb = 20*Qts^3.3*Vas

Fb = (Vas/Vb)^0.31*Fs

F3 = (Vas/Vb)^0.44*Fs

dBpeak = 20*LOG(Qts*(Vas/Vb)^0.3/0.4)

Vb = net box volume (litres)

Fb = box resonant frequency (Hz)

F3 = -3dB frequency (Hz)

dBpeak = maximum peak or dip in system response

Vas = Equivalent air compliance (litres)

Qts = total Q of the driver at its resonant frequency

Fs = resonance frequency of the driver (Hz)

Dv = internal diameter of port (cm)

Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)

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)

The value for k, the end correction, can be fine-tuned by using the following values to derive the appropriate end correction figure for each end of the port, then adding them together

Flanged End: 0.425

Free End: 0.307

e.g. if both ends were flanged,

k = 0.425 + 0.425 = 0.850

if one flanged, one free,

k = 0.425 + 0.307 = 0.732

if both ends were free,

k = 0.307 + 0.307 = 0.614

Normally, k=0.732 is assumed

Slot Ports

If you wish to use a slot port, first determine the diameter of a round port that has the same cross-sectional area as the slot. The following equation can be used to do this:

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

where,

Dv' = diameter of equivalent round port

W = width of slot

H = height of slot

 

[nVRuckus 5,000+ posts]

**** dave I havent seen you in awhile where you been hiding?

 

[baseballer1100 5,000+ posts]

Okay, here are the main box formulas, courtesy of DIYsubwoofers.org :
Vb = 20*Qts^3.3*Vas

Fb = (Vas/Vb)^0.31*Fs

F3 = (Vas/Vb)^0.44*Fs

dBpeak = 20*LOG(Qts*(Vas/Vb)^0.3/0.4)

Vb = net box volume (litres)

Fb = box resonant frequency (Hz)

F3 = -3dB frequency (Hz)

dBpeak = maximum peak or dip in system response

Vas = Equivalent air compliance (litres)

Qts = total Q of the driver at its resonant frequency

Fs = resonance frequency of the driver (Hz)

Dv = internal diameter of port (cm)

Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)

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)

The value for k, the end correction, can be fine-tuned by using the following values to derive the appropriate end correction figure for each end of the port, then adding them together

Flanged End: 0.425

Free End: 0.307

e.g. if both ends were flanged,

k = 0.425 + 0.425 = 0.850

if one flanged, one free,

k = 0.425 + 0.307 = 0.732

if both ends were free,

k = 0.307 + 0.307 = 0.614

Normally, k=0.732 is assumed

Slot Ports

If you wish to use a slot port, first determine the diameter of a round port that has the same cross-sectional area as the slot. The following equation can be used to do this:

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

where,

Dv' = diameter of equivalent round port

W = width of slot

H = height of slot

Once you've calcula

Woot Woot.

 

[Eugenics 5,000+ posts]

do you need more help building boxes lemans?

 

[PV Audio 5,000+ posts]

**** dave I havent seen you in awhile where you been hiding?

I've been working on getting into college, and now that I'm in, and more importantly, where I want to be, I decided to come back. After having seen the state of the forum upon my return, ain't nothin changed //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

do you need more help building boxes lemans?

//content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif :laugh: I'm alright, I could use a little more caulk though.

 

[baseballer1100 5,000+ posts]

Ok im confused on the calculations it says diameter wouldnt that be for a round port?

 

[Eugenics 5,000+ posts]

//content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif :laugh: I'm alright, I could use a little more caulk though.

caulk //content.invisioncic.com/y282845/emoticons/yumyum.gif.0556df42231b304b9c995aefd13928a8.gif

 

[PV Audio 5,000+ posts]

Ok im confused on the calculations it says diameter wouldnt that be for a round port?

You need to use the last formula to find out the equivalent surface area. Then, you just plug it back into the original equation //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[nVRuckus 5,000+ posts]

I've been working on getting into college, and now that I'm in, and more importantly, where I want to be, I decided to come back. After having seen the state of the forum upon my return, ain't nothin changed //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif


//content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif :laugh: I'm alright, I could use a little more caulk though.

yeah Im pretty much over it at this point. //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif I have no tollerance for anyone anymore.