Fluid Audio F4 (Pair) - 4" Active Studio Reference Monitors, White Frequency response: 69 Hz - 22 kHz Polarity: Positive signal at + input produces outward LF one displacement Input impedance: 20 k ohms balanced, 10 k ohms unbalanced Input sensitivity: 85 mV pink noise input produces 74dBA output SPL @ one meter with volume control at maximum Power: Fixed 110V ~50/60 Hz or 220V~50/60 Hz Protection: RF interference, output current limiting, overheat, on/off transient and subsonic filter