When does a port become to long??

 

Silver Member
Username: Rzarector

Coquitlam, Bc Canada

Post Number: 387
Registered: Dec-04
im building a box for my 15..
3 cu ft tuned to 30 hz and i got a port length of like 40 inches..
 

Gold Member
Username: Insearchofbass

Post Number: 2934
Registered: Jun-04
with a port that long youd need to do a slot port or split it up into smaller port tubes but that would be a bunch
 

Gold Member
Username: Insearchofbass

Post Number: 2935
Registered: Jun-04
im assuming you are acounting for port volocity
 

Gold Member
Username: Jonathan_f

GA USA

Post Number: 4167
Registered: May-04
What is the surface area of the port?
 

Gold Member
Username: Insearchofbass

Post Number: 2936
Registered: Jun-04
lets say you were using two 4 inch ports that totaled 40 inches long each for that port tune you would simply take the inner diameter and divide it by two and then your port length would be half its original depth

so youd get 4 two inch ports 20 inches deep compared to two 4 inch ports 40 inches deep
 

Gold Member
Username: Insearchofbass

Post Number: 2937
Registered: Jun-04
surface area is the inner diameter of the port times 3.1416 multiplied by the number of ports
 

Silver Member
Username: Rzarector

Coquitlam, Bc Canada

Post Number: 390
Registered: Dec-04
it is a slot port 17.32" x 2.5" 38.48 in long
cross area 43.30in^2
air velocity is 20.9 at 25 hz.. can u tell im using winisd :p
 

Gold Member
Username: Insearchofbass

Post Number: 2938
Registered: Jun-04
ill let jon handle this for you he will be more precise in his answer
 

Silver Member
Username: Rzarector

Coquitlam, Bc Canada

Post Number: 392
Registered: Dec-04
internal measurements btw
 

Silver Member
Username: Zacdavis

Beloit, Wi

Post Number: 118
Registered: Dec-03
the port should be 37.8 long with a true 3 cuft.
has the woofer displacement been accounted for?
 

SOLOs Rock
Unregistered guest
i want to build a ported box for my solo baric l7 12s someone please tell me how to do everything for this application. i've been reading for hours and searched to find a building program but i dont know the specs on my subs like the xmax i dont even know what that is. thanks a lot.
 

Silver Member
Username: Rzarector

Coquitlam, Bc Canada

Post Number: 397
Registered: Dec-04
im not sure .. does winisd pro do that automaticly or do u have to?
 

Gold Member
Username: Insearchofbass

Post Number: 2952
Registered: Jun-04
Id assume winisd does not factor in woofer displacement (room the sub takes up in a box) because they wouldnt be able to do it accurately you add this to your target net volume internal desired for your box. In this case the box volume is 3 cf net so youd add i dunno a random number here .15 sub displacement plus 3.00 cf net
desired the internal cubic feet would need to be 3.15 cf. you must also factor in port displacement. (room the port takes up in the box) Im also going to give you a link here that explains how to account for the port displacement and adjusting the port length properly.

http://forum.sounddomain.com/forum/ultimatebb.cgi?ubb=get_topic;f=11;t=060743

Copy and paste this link in a new window and it will work

ps....make sure you check that port length again for accurate port length for a 30 hz tune
 

Silver Member
Username: Rzarector

Coquitlam, Bc Canada

Post Number: 398
Registered: Dec-04
i know i understand how to add port volume and subwoofer displacement -- i just figured winisd pro would do the sub displacement automaticly.... since you add the size and displacement of the woofer when you enter one.. thanks though... i just want to know if a 38 inch long port is to long?? i dont want it to have slow response and sound muddy
 

Gold Member
Username: Insearchofbass

Post Number: 2966
Registered: Jun-04
oh if you add the displacement beforehand then your set assuming you put the right amount in. Now it wont sound bad because of the long port length
 

Silver Member
Username: Rzarector

Coquitlam, Bc Canada

Post Number: 400
Registered: Dec-04
really? id imagine that air travelling through a long port would lag and make the bass sloppy.. only one way to find out i guess .. build it!
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