The K2 S9900 has a single midrange crossover at 900Hz, blending one 1500AL-1 woofer to the 476Mg compression driver and horn combination. Above 900Hz, the HF compression driver and horn combination operates unassisted, all the way to 20kHz. The 045Be-1 UHF driver is brought in at 15kHz to cover 2 octaves of ultrasonic frequencies.