I've read much about the pros and cons of passive radiator systems and have owned a couple, one of which, the Altec Lansing 886a, I liked very much. I have also read how one of the chief advantages of a passive radiator is that using a passive radiator rather than a simple port allows for a much smaller net internal displacement for the same tuning. My question is this: does anyone know how to determine the optimum alignment, internal volume-wise for such an application?
My plan is to use two 8-inch drivers, Vas, 2.765 cu. ft., Fs, 39.67 Hz, Qes, .572, Qms, 3.87, Qts, .498, with a 12-inch passive radiator possessing a radiating area of 480 sq. cm and a moving mass of 200 grams. The radiator's native, unadorned moving mass of 200 grams will tune a 1.6 cu. ft. enclosure to appromimately 31.23 Hz, which is almost exactly the Fb arrived at using the 4th order equation; however, the 4th order equation for box volume produced a net displacement of 5.53 cubic feet, for which the moving mass would be only 44.556 grams, so, obviously, something other than a 4th order alignment is required to configure this system properly--but I simply don't know what it is. Anyone have a clue?