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View Full Version : Which is superior: Port area or port dimension ratio



matt_martin87
03-15-2006, 10:57 PM
I need to know what would be be better:

Either-
having the right port area (12.5 cuin) GOOD
but port ratio is 12:1 (12" x 1") BAD

OR-
having a good port ratio of 8:1 (12" x 1.5") GOOD
but port area is a bit too big (18 cuin instead of recommended 12-13cuin) BAD

Both have their ups and downs, but could you explain what the difference would be between them? Which one would be more appropriate?

Sorry if this is a bit confusing, but I will answer any questions you might have. Thanks.

amartin_72
03-16-2006, 09:13 AM
I have often wondered this too. And also what effect does the port area actually have? Besides making it big enough so there is no port noise, does it have any direct relation to the output ? Power handling ?

dbornotdb
03-16-2006, 09:17 AM
Why don't you step up to 25.16 sqin (equilelent to adding another 4" port) and just re-work the length.

You seem to be wanting to make the ports opening 12" long. So then you can make it 2" wide. That gives you a ratio you can be proud of.}-]

dbornotdb
03-16-2006, 09:19 AM
I have often wondered this too. And also what effect does the port area actually have? Besides making it big enough so there is no port noise, does it have any direct relation to the output ? Power handling ?



If the port is too small or the opening is not wide enough, you will have port compression at the opening inside the box.

amartin_72
03-16-2006, 09:31 AM
Can the port area be too large? For a 12, most of my boxes i make are about 30in^2 but what would say a 50 or 60in port do? as long as it was long enough to maintain the same tuning.

dbornotdb
03-16-2006, 09:36 AM
Well you wouldn't want the port so big that the sub ends up acting like it is in an open baffle. You want the port walls to be long enough so the backwave of the sub is seperated from the front wave. Or it will just cancell itself out.

matt_martin87
03-16-2006, 12:01 PM
This is for an 12" Adire Shiva. I've been in contact with their tech guy and he recommends 12.5 sqin of port area. This is a fairly small sub for those who aren't familiar with it.

I absolutely cannot fit a 2" wide port on this box. The width of the box is 15" and 1.5" is the max I can go for width.

My plan at the moment is to just use the proper port ratio of 8:1 and use 18sqin of port area.

Volenti
03-17-2006, 02:58 AM
Can the port area be too large? For a 12, most of my boxes i make are about 30in^2 but what would say a 50 or 60in port do? as long as it was long enough to maintain the same tuning.


Is this too much port area? :D

http://users.bigpond.net.au/volenti/TL_spl.jpg

http://users.bigpond.net.au/volenti/TL_spl2.jpg

You start to get transmission line effects as the port length gets longer than 3' or so, make the port big enough and long enough and eventualy the transmission line effect will start to dominate the response, this is the basis behind the T-box by Hexibase.

davidfre21
03-17-2006, 02:59 AM
thats a cool lookin box :D

Mr. Opportunist
03-17-2006, 03:01 AM
thats a cool lookin box :D
x2

SPL140.2
03-17-2006, 03:36 AM
What kind of numbers you hittin with that enclosure???