Need help building a box

It is too small

I'm gonna agree with AZN on box size, but I would change the tuning to 38 - 40 Hz. Also the area taken up by the port is not part of te 2.5 cu ft recommended

I like this one, increase the width of the box to 34 inches

 

why search for plans when you can get some paper and a pencil and draw them out yourself

 

Here is what I would do, Increase the width of the box to 34-inches as I stated earlier.

Port length needs to be adjusted. Look at your plans, where it shows the 13.375 length. Change that length to 8.5-inches. That sould get everything where it needs to be.

 

ivancho its Hz not MHz.

 

No No No

Try this, double check my numbers

 

And I thought that I was the only one who was confused

 

Good now build it, and take your time.

Rush jobs always look and sound like rush jobs

So Take your time and Have fun

 

Ranger, you just using your brain on this? or is there something else on your plan?

 

What do you mean? lol

 

If he's like using strait math or one of them programs that just does it for you

 

Ranger loves math

 

Well damn, how do you find out what size your port(s) needs to be

 

Port Length
The port length required to tune a volume of air to a specific frequency can be calculated by using the following equation:

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

where,

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)

port.gif (1467 bytes)

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

In practice, it's best to use ports that are slightly longer than predicted by the above equations, then adjust their length until the correct tuning is achieved. It is much easier to shorten a port than to lengthen it!

Minimum Port Diameter
To calculate the minimum diameter of the port required to prevent port noises, you will also need to know the following:

Xmax = maximum linear displacement (mm)
Dia = Effective diameter of driver (cm)
Np = number of ports

Calculate the minimum port diameter from the following equations:

Sd = pi*(Dia/100)^2/4
Vd = Sd*Xmax/1000
Dmin = 100*(20.3*(Vd^2/Fb)^0.25)/Np^.5

where,

Dmin = minimum port diameter (cm)

Note: You CAN use ports that have a smaller diameter than that given by the equation above, especially if the ports are flared at both ends. However, at higher volumes, you may notice some port noise caused by the air rushing through the ports.

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 calculated Dv', you can use it in the equation for Lv above to determine the required length of the slot port to tune the enclosure to the required frequency (Fb).

Taken from here
http://www.diysubwoofers.org/misc/portcal.htm

 

Huh? LOL Getting irritated just looking at those formulas

 

I'm not sure how to get the net volume in liters, that's the only part I got confused on.