Acoustic Research AR-1 - 3-post Backplate

Acoustic Research AR-1 - 7-post Backplate

Design Acoustics D-6

Dahlquist DQ-20 Low Pass Filter

Dahlquist DQ-20 Mid/Treble Filter

Dahlquist DQ-20i Mid/Treble Filter

Dynaco A-25

Electro-Voice X8 and X36 and related self-contained crossover networks (circa 1960s):

Advent/1

Smaller Advent

Klipschorn type ak-3

Klipsch Chorus II

Klipsch Type-A

Klipsch Type-AA

Klipsch Chorus I