port area question

[stl_314 10+ year member]

Why does everyone say your port area needs to be based on the size of your box? I have read posts on fb now were obsidian and dc both have said go by driver (ie. 15 needs this much, 18 needs this much. not even worried about the box size)

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[hispls 5,000+ posts]

Whatever number they give probably assumes you're using the proper volume for that size sub. Really the old conventional wisdom used to be based on cone area, but basing by box volume seems to work well enough in practice.

 

[RAM_Designs 5,000+ posts]

Because really, required port area has absolutely nothing to do with what size box the sub is in. Whether it's in 1ft^3 or 5ft^3, the air displaced by the sub is going to be the big determinant of what is the "safe zone" for avoiding port noise. It's just that people tend to use the same size box for 10's 12's etc, so the rule of thumb tends to be ok in most cases.

I know Nick at Obsidian is a big supporter of NOT using large ports, but using smaller aeros to maintain extension below tuning and keep peakiness down. And with aeros, it's easy to use a smaller port and not have to worry about port noise.

 

[stl_314 10+ year member]

My view on it though is, 18's can go from 4cubes to 10cubes depending on the sub. So thats over double the port area depending on the size of the box. So why does everyone keep recomending 15 in per cube. Why not start letting people know that is not the way to do it

 

[RAM_Designs 5,000+ posts]

My view on it though is, 18's can go from 4cubes to 10cubes depending on the sub. So thats over double the port area depending on the size of the box. So why does everyone keep recomending 15 in per cube. Why not start letting people know that is not the way to do it

Because people don't listen and are stuck in their ways...they will always recommend 12-16in^2 of port per ft^3.

 

[Moble Enclosurs 10+ year member]

No kidding. I dont know where that originated from, but get rid of that rule.

 

[pro-rabbit 5,000+ posts]

Because people don't listen and are stuck in their ways...they will always recommend 12-16in^2 of port per ft^3.

It is also hard to get people to look past this do to several companies suggesting this very method. With "dumb luck" it does tend to work some times.

 

[travicles 10+ year member]

I am interested in this. So if that rule should not be followed, what is the correct way to determine port area? Also, what is the difference between a small port and larger port? I have read a larger port creates a more peaky response, but I don't know if that is true.