superior quality i connect two jbl gto 649c component speaker and sony 1800 watts sub woofer excellent sound quality input gain setting adjustment is important get good sound quality because it was 70 watts rms per channel so we set the voltage use multimeter in plus minus of speaker output is 1673 volt in 1 khz test tone play in head unit with 75 volume1673 volt is get formula is speaker ohms rms of amplifier per speaker and squreroot the value example 4 ohms speaker 70 280 a