STX EQ-231 2 x 31 - Band stereo graphic equalizer
STX SC-202 Active 2 way stereo crossover with subwoofer channel Low / High crossover range: 250 Hz - 6 kHz Subwoofer crossover range: 50 Hz - 250 Hz
STX SC-203 Active 3 way stereo crossover with subwoofer channel Low / Mid crossover range: 70 Hz - 1 kHz Mid / High crossover range: 480 Hz - 7000 Hz Subwoofer crossover range: 50 Hz - 250 Hz