The In Phase Car Audio XTB-828R Underseat Subwoofer is a passive radiator equipped active sealed subwoofer enclosure. Hit really low frequencies and experience true bass accuracy not normally found in bog-standard active subwoofer. Equipped with an all weather glass fibre woven cone 20cm (8") drive unit, paired with a passive radiator in sealed enclosure technology, it provides deep and controlled bass frequencies. Its built-in 400W class D amplifier offers high power handling and numerous controls.XTB-828R has high and low level inputs that can be plugged with after market and OEM headunits.This FOUR-in-one enclosure reduces overall dimensions while offering a great bass level. This comes complete with a wiring kit apart from RCA cables. If fitting to an aftermarket headunit, you will need RCA cables