It is a double 18" subwoofer and used for indoor bass shortage . Also it can be used for larger area .
Detailed introduction to TA-228B Low-frequency loudspeaker system:
DUAL18"SUB-BASS SPEAKER SYSTEM
Power Hading 1000W(MAX/1200W)
Frequency Range 30-500KHz(±3dB)
Nominal impedence 4Ω
Sensitivity 98dB/1W/1M
Drivet complement 2x18"
Dimensions (H x W x D)750x1050x710(mm)
Box Material Plywood