For speakers with sensitivities between 80dB and 98dB. On the rear of each unit are crossover and level controls and banana plug/binding post connectors. The crossover point can be set at 15, 17 or 20 kHz via a switch controlled 3-way high-pass filter which ensures minimal phase shift. A wire wound L-pad variable attenuator allows adjustment of the output of these units. Were being used with my Fostex 206 BLH Horns, also for sale. Can Post these.