[Lucky7!]

Re: port dimensions vs speaker size

Port size depends upon the tuning of the box, and it's size. It also depends upon the volume of air that it needs to move to keep the speed low enough (<0.05 Mach is my preference) not to chuff or make discernible noise.
Download Unibox, throw the T/S parameters in for your driver and start modelling. Remember to update graphs after each mod and look at the tabs on the bottom line for more.

 

[Lucky7!]

Re: port dimensions vs speaker size

Yeah I'm ok with tuning etc, just haven't played with ports longer than 4-5 x the diameter, not modelled but in the real world. From my experience somethings that aren't noticable in speakers and amps make a difference to the human ear and sometimes tiny changes in equiptment sounds way different.

My experience is that the modelling of tuned bass enclosures is very accurate to real world (measured) results. The maths for how to tune enclosure has been known for 30 years and is now easy to change it quickly and graph it easily.

Port length to diameter ratio is meaningless without knowing what sort of mass of air you are capable of moving and the speed of it through the selected port. Port noise and chuffing can be very audible and the only way to get this info is to model or measure.

If you've been tuning enclosures in the part, have you been measuring the impedance curve to se the tune?