View Full Version : Determining Port Area

06-25-2010, 10:50 AM
Alright i was wondering if there a equation or a given rule to determining the port area for a ported box

because i have seen people use really big ports and some using really small ports

if there is a way to determine the correct port area with a possible relation to the the speakers xmax

thanks for any help recieved

06-25-2010, 11:22 AM
port area is generally 16 cu. in. per cu. ft. of air space. You probably see smaller ports on smaller boxes and port area is just width x height so you can have a skinny but tall port or a smaller square port. If you go too small you'll get port noise, I've had that and it is very unpleasent.

06-25-2010, 11:52 AM
okay so there is really no relation between xmax and port area because for every box i have made i used somewhere between 12 to 18 i believe depending on the size of the sub

because im making a box for a 10 and i plan on using 12 sq for a 1 cubic box tuned to 36hz

06-25-2010, 11:55 AM
Personally, I'm running 15.4 so I don't get port noise because I'm just under but 12 is kinda pushing it. You may end up with port noise on certain frequencies.

06-25-2010, 12:01 PM
It really depends on the amount of power you plan to use also. Some fantastic home speakers use very small ports in large boxes. It works because you have low power, low x-max

Port turbulence has to do with velocity of air in the port. The more air you're trying to move in it the more you're likely to run into port noise.

All that being said, it seems to be the conventional wisdom (backed up to a large degree by measurable repeatable results) that large ports are louder. The tradeoff of course is the length will often becom impractical particularly in small boxes with low tuning.

06-25-2010, 12:09 PM
yeah i have really noticed that problem with long ports well the most power this sub will be seeing is 500 at max

06-25-2010, 05:15 PM
There is a general rule of 12-16 sq. inches of port for a slot ported box

06-26-2010, 04:02 PM
I use 12-14in^2 per ft^3, normally closer to 12...I tune too low to go any bigger. :D

Never had port noise issues either.