Port volume to box volume ratio


CarAudio.com Newbie
Sep 9, 2018
Phoenix, AZ
This might be a stupid question but how to you optimize the port volume to the box volume. It appears you can change the port volume as long as the ratio of length to area of the port is the same and keep the tuning. How do you optimize this for the most power output? If the port volume is too small not enough air will be able to move and if it is too big there will not be enough pressure for the driver. I am using your average circular port for this design. Thanks!


10+ year member
Dec 29, 2001
Lawrence, KS
It's a matter of port noise - which is created by high air velocity. From messing with WinISD the size of the port makes no difference in sound quality other than creating noise if it's too small. So there's no "optimal" size although I have often seen 12 sq in port area per 1 cu ft net box volume. You'd definitely want to err on the too big side, but at some point you're just making a larger enclosure for no improvement in performance. That's why it's good to be familiar with modeling.


Nov 19, 2017
It depends on your power/volume/tune.
There's no magic formula other than keeping the velocities under a certain point.
Aeros with large flares can help with port size and allow for slightly less port area for a specific volume/power at whatever tuning you're at.
But 100fps is my limit with a slot... 115 with an Aero possibly a bit more.
The advice above is spot on imo, so I thought I'd expand on it.
Modeling with your power/volume/ tuning is the closest you'll get to your goals and when it is off a bit you'll be able to see or approximate where you need changes.
My .02

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