4th order port ratio?

[ncc74656]

im looking into a 4th order, for the port itself i believe i understand how the port area needs to relate to the cone area of the sub. my plan was to put it at 1:0.5 ratio there. my real question is what should the port size ratio be for a 4th order? a standard ported box should be no larger than 1:9 ratio from what i had read. is there a rule like this for a 4th order?

e.g. 10X10 vs a 2X20 and such?

is there a minimum ratio to be above?

[TaylorFade]

The 9:1 rule of thumb applies to any port.

[Hugh G. Rection]

The 9:1 rule of thumb applies to any port

interesting theory.