Long Port options
Some suggestions for when the port length is greater than the box size
When a ported subwoofer is tuned low, and uses ports large enough to keep airspeed to a reasonable level, the result can be long ports. Here are a few ideas to help you deal with them.....
Run external ports
See more on the Sidewinder sub
Fold the port up inside the box
See more on the Snorky sub
Build a concentric port
Someone else might be able to refine the design to make it workable
See my notes
Use a Spiral port
See more on Genelec Subs (offsite link)
Build rectangular port into the box walls
See more on Slot port flaring
Flange both ends of your port
See more on smoothing rings
Use port flares
See more on Port Flares
Increase box size slightlyFor a given tuning frequency, as box volume increases, the port length decreases. This option increases air velocity, so careful modelling is needed. Worth exploring if a modest saving in length saves having to use a bend in your port.
Lower tuning frequency slightlyPort airspeed varies with frequency and peaks at the tuning frequency. For borderline designs, dropping tuning a little may decrease velocity enough to allow a smaller diameter port, which will be shorter
If you think some of these designs are convoluted, you'll be amazed at the folded horn gallery at fullrangedriver.com
Surely with all these options you'll never get a port noise complaint ever again!