Boston Acoustics Horizon Series HS50 Midnight Speaker(Each) (Discontinued by Manufacturer) Deep Channel Design (DCD) for more bass from less amplifier power Reduced Baffle Diffraction Design (RBDD) for wider, smoother dispersion Recommended Amplifier Power - 10-125 watts Nominal Impedance - 8-ohms Frequency Response (3dB) - 65Hz-25kHz