The commercial equipment included in the system is pretty mundane:

Custom Active Crossover

  The active crossover in the system was originally supplied by an Audio Control Richter Scale - yes, the original one, obtained about two months after release. It even came with a "beta" manual. Its major design flaw, at least as far as this system, was the asymmetrical 18 dB / 6 dB crossover. The subs pass on far too much high frequency information, requiring close placement to the satellites. This defeats the purpose of separating the low frequency drivers, of course, so a better crossover was designed from scratch. The second problem was that the subwoofer design is a 6th order Chebyshev alignment, requiring an external filter to achieve flat response. The "bass boost" circuit in the Richter Scale is similar, but not the correct filter alignment to complement the box tuning.

  The new crossover is a Linkwitz-Riley 4th order design, with the auxiliary filter included in the design. It was breadboarded on standard perf board, after assembly and debugging on a 3M breadboard. The power supply is a fairly typical +/- 15v supply using LM317/337 regulators. The whole crossover is built into a metal chassis with a separate "chamber" for the power supply.