Actually, I came across some indication that Audiotechniques made electronics crossovers for the Altec duplex speakers, so perhaps this is some of their work. I came across this:

Another control room goody that can be built with a state-variable filter is an electronic crossover for bi-amping, or for that subwoofer you've always wanted. Taking advantage of the simultaneous high-pass and low-pass outputs, we get precisely complimentary curves that fall at a rate of 12 dB. per octave. There has been a lot of talk lately about the advantages of using 18 dB. per octave slopes, so I contacted Altec, JBL, and Audiotechniques (Big Red monitors) for their recommendations. JBL was emphatic that 12 dB. per octave crossovers should be used with their components, and Audiotechniques also felt that this would create less ringing and phase shift than the 18 dB. types. On the other hand, Bob Davis explained that Altec offers crossovers in several formats, and as such he couldn't endorse any particular design.