How may ports? (1 Viewer)

[Bobby T]

I'm about ready to start ordering everything I need to finish my first sub. The last thing I need to know is are 2 shorter ports better than 1 long one? I ask because I noticed my Paradigm has 2 4" ports that are 9" long. It was recommended to me to use 1 4" port that is 16" long. The boxes external measurements are

L 24"

W 15"

H 17"

I'll be using a 12" Dayton or Titanic with a 250 watt PE plate amp and stuffing the box.

 

[Dave Poehlman]

Bobby, it's not as easy as simply cutting your vent in half. Actually, each vent would need to be longer than the original 16" vent.

I'm sure someone here could explain why that is.. I've never been able to understand it, its just how the formula works out.

 

[Bobby T]

The original vent on this box is only 6" deep, 1 1/2" high, and 15" wide. Based on recommendations from this forum I'm sealing the vent and putting in a 4" port that is 16" long. I was just curious if I should use 2 ports since I noticed that was how my 12" Paradigm was built.

 

[Ron D Core]

The biggest reason why you would want to add more ports or make their cross sections bigger is either increase efficiency or reduce the air velocity. If you want to do more ports you have to take into account their cross section and convert that to a diameter depending on what program you use. Its most helpful with a higher excursion driver and alot of power where the air compression will be high, thus creating alot of port noise. Just remember you'll have to be able to get the ports in the box you have in mind.

 

[Isaac C]

Dave is right, "to keep the same tuning frequency" you'd need longer ports when using more vents.
As for why -- http://www.hometheaterforum.com/htfo...threadid=20387
Please note that the given delta Lv is for two flanged ends.
hth
Isaac

 

[Bobby T]

I'm starting to understand more,thanks everyone. I still have a lot of learning to do. Looks like I need to stay with one port. Now can someone explain to me how to tell how low a box is tuned to?

 

[Isaac C]

Now can someone explain to me how to tell how low a box is tuned to?

If you'd follow the link I gave above, you'd know the answer to this question.

 

[Bobby T]

Sorry Isaac. I saved the link but did not have time to look at it yet. Thanks again.