Bass reflex enclosure

[Opie]

Hello all,
I am building a subwoofer and I am trying to figure out what port diameter to use. The factory specs for the sub say that I should use a 2.5 inch diameter port tube, but this is only for one port. My question is wheather I can use 2 ports of 2 inch diameter? Will I have problem with port turbulence because of the smaller size?


I don't know what I would do if I didn't have this forum to answer my questions.

Opie

 

[Super]

I would say yes. Theres a good chance that you'll get huffing noises coming from ports that small in diameter. Your better off going with the larger port.

 

[kelticwizard]

The (2) 2" tubes will have to be longer than the one 2.5" port.

Just for the heck of it, what size enclosure are you planning, what tuning frequency, and which driver? I wouldn't use (2) 2" ports for anything over a 10 inch driver.

 

[Opie]

I plan to use a 10" sub tuned to 32 hz in 1.2cu ft enclosure. The port length will be 12in using two ports.


Opie

 

[GRollins]

Bear in mind that the longer the port is, the more it tends to achieve a life of its own. The air acquires enough momentum that it becomes difficult to stop once it begins moving. As such, you get a lag between the port response and the driver; a distortion mechanism, in other words.
Better to use a short port...but then you end up with it being narrow in cross section, hence more likely to make noise.
Your choice--just be aware of the tradeoffs.

Grey

 

[zx-tex]

If you REALLY want to know about the port size, you could download WinISD and enter in your speaker parameters if you know them. It has a utility that determines the mach number (air speed velocity) in the port for a given size. It can give you and idea if your port is too small or not.

Just a suggestion. Good luck!