N604-16A
The Great Plains Audio Model N1600-16A is new passive crossover network designed specifically to provide smooth response from the Altec Lansing Models 604, 604B, 604C, 604D, 604E, 605B Loudspeaker throughout its bandwidth. This combination results in a speaker system that is ideal for use in home theatre and high-quality audiophile systems, recording studios, and professional sound system installations.
Specifications to be found on the GPA Website