I know that too small a port area will lead to port noise, but what happens if you have excessive port area? For example 20 sq inches per cubic ft of volume? I know many manufactures recommend 12-16 inches per cubic foot of volume, but is there a downside to going over this?

go to big and sub will sound sloppy or bottom out ... got to find a sweet spot..

How much is too much though? I am building an enclosure for a 12" BTL, Fi recommends 16 sq inches per cubic ft, but most calculators and box building programs that I have been playing with suggest higher. Would 2.5 cubic ft with 43.5 square inches of port be too much?

If there's too much port area,

the velocity will be too low and

the subs will bottom out due to

lack of proper resistance.

If they say 12-16sq.in. per cf3 then I'd try to not

deviate from that too much.

Shoot, 43 sq. inches isn't at all too much for a 12. 12-16 sq. inches isn't even enough for some subs in some cases. I don't think you need to really worry until you get up near the sub's cone area in port size. For your 12, that means probably 80 sq. inches or so.

How much is too much though? I am building an enclosure for a 12" BTL, Fi recommends 16 sq inches per cubic ft, but most calculators and box building programs that I have been playing with suggest higher. Would 2.5 cubic ft with 43.5 square inches of port be too much?

43.5 sq inches would be fine in 2.5cubes... it's pretty close to the 16sq in per cubic foot rule (the rule you stated)

I use 25 sq in per cube and thats not too much. Excursion was less than half of that in a sealed enclosure. Bottoming out is not a problem.

I don't know what people are talking about when saying too much makes the sub sound sloppy or bottom out.

try this:

Port Size Calculator

input the driver size, and the Xmax, it'll give you the recommended cross-sectional area of the port. plus-or-minus 10%, you should be fine.

I use 25 sq in per cube and thats not too much. Excursion was less than half of that in a sealed enclosure. Bottoming out is not a problem.

I don't know what people are talking about when saying too much makes the sub sound sloppy or bottom out.

depends on the sub... you cant say going over the 12-16 rule will make every sub sound sloppy but it will with some and for others it wont be enough... but all in alll too much port area will result in bottoming out when played with too much power or under tunning and it will bottom out easier but it all depends on the sub

I don't know what people are talking about when saying too much makes the sub sound sloppy or bottom out.

If the port is too large it behaves less as a port and more as a big hole in the box, basically making the sub think free air. The sub has to be able to excite the air in the port predictably.

And some drivers won't even be able to excite enough air to make smaller ports ineffective either. Just use what is recommended. the manufacturers know their products better than anyone else. They make recommendations for a reason.

And some drivers won't even be able to excite enough air to make smaller ports ineffective either. Just use what is recommended. the manufacturers know their products better than anyone else. They make recommendations for a reason.

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