Re: Ported box?
There are a number of websites that explain enclosure design. Basic Car Audio Electronics and DIY Subwoofers are both good. I know BCAE has a port calculator but I'm not sure about the latter.
As for volumes of ports, braces and drivers, they must all be add to the net volume you're looking for. So for instance, if you calculate a 1 cube box with 30Hz tuning, you'll need to add the displacement of the driver, port and any bracing you may need. That'll usually push the box size up to 1.5-1.75 cubes depending on the driver size and port type/length.
A good rule of thumb when selecting a box type is efficiency bandwidth product (EBP). This value is derived from dividing driver Fs by Qes. Drivers below 50 generally do better in sealed or 4th order boxes, those between 50 & 75 do well in both and those above 75 do best in ported or 6th order boxes. Moreover, drivers with a low EBP will require larger ported boxes in order to yield a flat response while those with high EBP will perform well in smaller ported enclosures.
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