The design is a dual chamber reflex, as soon as I saw it I dug out some of my old Speaker Builder magazines.
If you are really interested in this design, look up the first issue of 1992. That issue has a four page artical on the design, or look up the"Augspurger's System" on the internet,there might be something there to help you.
But basicly
1 A double-chamber reflex, with the first chamber having twice the cubic volume of the second one and with three ports of equal dimension is tuned to two frequencies that are about an octave apart,
2 At lower frequentcies of resonance the driver sees the system as if the partition didn't exist .
so to build one all you have to do is figure out how big the box can be,has to be same size or larger than the suitable vented enclosure for the driver you are using.
Then divide that volume into thirds, the volume with the driver takes two thirds, and the other volume one third.
Figure out the area of the vents to use so there will be low port noise.
Then caculate the length by using two times the vent area,the full enclosure volume,and the lower frequency of resonance.
If you are not familiar with port length caculations, Ill try to make this simple
2
2117 X d
L= ------------------- - 0.732 X d
2
F X V
b b
L is the length of the port (the answer you are looking for) in inches
d is the diameter in inches
F is frequency you are tuning for
b
V is the volume of the box you are tuning (in cubic feet)
b
hope this helps, it has been a long time since I did any of this
My G.N. takes all of my time now.