The crossover sits between the DQ-10 speakers and the DQ-1W subwoofer. Basically, the amp is connected to the external crossover, and the crossover does it's thing. It sums the left and right channel signals into one for the subwoofer output. The left and right channel cut-offs are variable (a three position switch, I believe). The output of the subwoofer can be phase-adjusted (with a toggle switch - 0 and 180), and the subwoofer output level can be adjusted (L/M/H). Nothing infinitely variable here.
The guts of the crossover are more or less what you would expect - caps for the cut-off frequencies and resistors for the volume control. Then there are two items that look to me more like transformers than the inductors I see in conventional cross-over designs. The caps are all high value, non-polarized generic models (80, 160, and 400 uF).
Sorry I can't provide more detail. That's about the extent of my technical knowledge. I guess I was just wondering if you had ever taken a look at one of these rascals to see if the design could be improved. I a big fan of Jon Dalhquist, but it's been 30 years since he designed this thing. I'm guessing that the conventional wisdom about cross-overs might have evolved since then.
Whatever comes of this inquiry will likely be temporary. I'm planning to have a set of HT-3's by this time next year. Can I interest you or Jim in a trade-in?