A few Mag box questions

[klepto 10+ year member]

From what i have read, when porting a Mag you want to run anywhere from 2-2.5 cu^3 ft NET @30-32 hz with anywhere from 30-50sq inches of port. Few questions.

What will the audible difference be from 2-2.5 cu^3 ft. Tighter bass with smaller box? What does it mean "NET" volume? Does that mean you take the total internal ft^3 of the box and subtract the displacement of the sub, in my case .15, and that is your NET displacement?

How does the total SQ in of port effect the sound and behaivor of the driver? Would making a labarenth port be the best way to lengthen it, or would simply making the port wider suffice. Thanks.

Klep

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[xluben 10+ year member]

this is a mag 12 i'm assuming.

the difference from 2 - 2.25 ft^3 will be fairly minial, but if you compare 2.25 ft^3 then you'll notice the larger box has a more flat response that will extend deeper, whil the smaller box will be more peaked with less low bass.

net volume is internal volume minus driver displacement minus port displacement.

the more power area you have (in^2) the less chance you'll have to hearing port noise. the more port area you have the longer the port will have to be to reacha desired tuning frequency. labyrinth style ports work if that is the only way to fit a long port into a box, but the 180 degree turns can cause air turbulence and increase the chance of port noise. an l-shaped port would be better.

 

[klepto 10+ year member]

this is a mag 12 i'm assuming.
the difference from 2 - 2.25 ft^3 will be fairly minial, but if you compare 2.25 ft^3 then you'll notice the larger box has a more flat response that will extend deeper, whil the smaller box will be more peaked with less low bass.

net volume is internal volume minus driver displacement minus port displacement.

the more power area you have (in^2) the less chance you'll have to hearing port noise. the more port area you have the longer the port will have to be to reacha desired tuning frequency. labyrinth style ports work if that is the only way to fit a long port into a box, but the 180 degree turns can cause air turbulence and increase the chance of port noise. an l-shaped port would be better.

So given the range of 30-50sq in of port, i should try to have as much port area as possible? I chose this design for my sub.... http://img29.imageshack.us/my.php?image=25cubes32hz3125sqin0zp.png

2.5 @32

Am i correct to assume that 2.5 cu^3ft in that mock up does not take into account port area and driver displacement?

How could i make more port are without changing the frequency, making the port wider? Is too wide of a port a bad thing?

 

[xluben 10+ year member]

that box looks good.

moe's plans do take into account port and driver displacement.

making the port wider would require a longer port to get the same tuning, which would in turn make the net volume of the box smaller.

i'd just do that box, or give me the max dimension you can fit, and how wide you want the port to be.

 

[klepto 10+ year member]

http://img29.imageshack.us/my.php?image=25cubes32hz3125sqin0zp.png

No, that box fits my car just fine but i was reccomended to have between 30-50Sq inches of port. Looking at that box it looks like there is about 70.5 Sq inches of port. Are my calcularions correct or am i *** backwards...

 

[xluben 10+ year member]

12.5in * 2.5in = 31.25in^2

should be enough port area, but if you want more just let me know what your dimensions are and i can get something with subwoofertools.

 

[klepto 10+ year member]

I know the 2.5 is the width of the port, but where did you get 12.5 from? Pretty sure i am happy witht his box but would you reccomend more port area to be ideal?

And btw my trunk is 38'' wide x 22'' depth x 19'' height.

 

[xluben 10+ year member]

14" tall box

2 pieces of 0.75" MDF (top and bottom)

14" - ( 0.75" * 2 ) = 12.5" tall port.

http://www.subwoofertools.com/forum/ported-box.asp?Ew=38&Eh=16&Dia=6&Xmax=25&Vd=.12&NumW=1&Vb=2.5&Fb=32&Qts=&Vas=&Fs=&CE=0

that could save you some trunk space by utilzing the whole width of the trunk.

and it's got a little more port area.

either box should work fine, though.