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mackin
04-20-2008, 10:50 PM
I am having some serious trouble trying to design a box for 2 12 inch Diamond D6's. I am trying to follow nG's "Simple EDU" post but apparently i don't know enough about enclosures to follow it.

The dimensions I chose to work with were a width of 35 and a height of 16, leaving the depth as the variable.

In winISD, i typed in the NET volume of 2.5, along with a tuning of 32 hz.

Where i became confused, was how much port area i should give the subs. i typed in 4 inches for the width of the port, and 14.5 for the height of the port. It then gave me a length of 54.51. is 4 inches too wide?

does 54.51 sound right for the port length? is this going to give a proper amount of port area and the correct tuning of 32hz?

Thanks in advance, any help or advice is appreciated. :veryhapp: :crap:

BrianChia
04-21-2008, 02:54 AM
The port area depends on many different issues such as the excursion of the driver, the power supplied, and the size of the enclosure. One way to check is to go the the tabin WinISD that displays the graph entitled "Rear port - air velocity", then enter the maximum power that your subwoofer will see (you MUST use the correct specs of your actual driver and also choose the correct number of subs and correct enclosure size). The said graph will display the air velocity through the vent over a range of frequencies for the amount of power you select. A good guide is to keep the peak frequency below 34 m/s, which is 1/10 the speed of sound. If you stay below this number you should not have port noise problems.

A simpler guideline (though not as telling) is simply to use 12-16 sq. in of port area per cubic foot of the net enclosure volume, using more (16 sq. in/cf) if the driver has higher Xmax and lower if it has less Xmax.

As for as your box is concerned, you should be fine with a 3 in. widex 14.5" port. This will cut down the port length and reduce the overall enclosure size.

mackin
04-21-2008, 04:08 PM
The port area depends on many different issues such as the excursion of the driver, the power supplied, and the size of the enclosure. One way to check is to go the the tabin WinISD that displays the graph entitled "Rear port - air velocity", then enter the maximum power that your subwoofer will see (you MUST use the correct specs of your actual driver and also choose the correct number of subs and correct enclosure size). The said graph will display the air velocity through the vent over a range of frequencies for the amount of power you select. A good guide is to keep the peak frequency below 34 m/s, which is 1/10 the speed of sound. If you stay below this number you should not have port noise problems.

A simpler guideline (though not as telling) is simply to use 12-16 sq. in of port area per cubic foot of the net enclosure volume, using more (16 sq. in/cf) if the driver has higher Xmax and lower if it has less Xmax.

As for as your box is concerned, you should be fine with a 3 in. widex 14.5" port. This will cut down the port length and reduce the overall enclosure size.

Thanks for your reply. for example, what Xmax would correspond with a lower sq in of port area? I don't know enough about different subwoofers to know if it has a high xmax, average xmax etc..

By the way, the xmax is 16.5

Also, there was an option for end correction. what does that mean??

mackin
04-21-2008, 09:43 PM
Any ideas on how much port area? xmax is 16.5 and it is 2 12's in 2.5 cubes NET.

What does end correction mean?

Thanks.

BrianChia
04-21-2008, 10:41 PM
40 sq inches in plenty enough. If your box is 14.5" tall (internal) then do a 14.5" x 3" port. That gives 43.5 sq in which is more than enough.

As for end correction, just leave it at the default setting (1 flanged end), but remember that when measuring a slot port, add 1/2*(the width of the port) when measuring down the middle. Like this (the effective port length is measured down the center line):

http://img519.imageshack.us/img519/6389/portlengthyd0.png

mackin
04-22-2008, 03:57 PM
40 sq inches in plenty enough. If your box is 14.5" tall (internal) then do a 14.5" x 3" port. That gives 43.5 sq in which is more than enough.

As for end correction, just leave it at the default setting (1 flanged end), but remember that when measuring a slot port, add 1/2*(the width of the port) when measuring down the middle. Like this (the effective port length is measured down the center line):

http://img519.imageshack.us/img519/6389/portlengthyd0.png

Thanks for the image that definitely helps me visualize it :)

Can i arrange the port any way i see fit as long as it is the correct length and area? Does one flanged end just mean an L shape?

Thanks again for your help.

miker
04-22-2008, 04:10 PM
So you want about 58 sq" port...

mackin
04-22-2008, 10:03 PM
So you want about 58 sq" port...

well maybe by what i was doing before. but now it sounds like 43.5 :veryhapp: