Please kindly look at the below description of B Srx700 Series Srx-718s Stage Light:

Model	Picture	Configuration			Impedance	Power(RMS)
		LF	MF	HF (Voice Coil)
SRX-718S		1× 18 Sub bass                                                                      Voice Coil:   4' '                       Magnet: 8 (200mm)			8 Ohms	600W
SRX-728S		2× 18 Sub bass                                                                      Voice Coil: 4' '                       Magnet: 8 (200mm)			4 Ohms	1200W