XTB-828R 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 cablesWhat on Earth is a 'passive radiator'?A Passive Radiator is a speaker with no voice coil or magnet, basically a speaker cone. This is not connected to the amp at all. The purpose of this speaker is to allow the trapped sound pressure in the sealed enclosure to excite a resonance that makes it easier for the speaker system to create the deepest pitches (e.g bassline). In short, it gives you the benefit of ported enclosures without the downsides. This leads to better sound quality, with a linear frequency response of the sealed cabinet and the higher output you get from a ported design. This is also achieved in a smaller size than the ported subwoofer. You also do not have the same issues with port noise, and instead, you end up with a smooth bass.Class D AmplifierA robust, compact and efficient Class D amplifier is mounted to this enclosure. This is the driving force behind the sub. Only the finest components in it's category will do. Offering up to 400W peak and 200W RMS PowerCompact DesignThis sub is only the size of a small desktop computer case. This small footprint allows the user to add thumping bass without compromising space in the boot.Superior Subwoofer ConeThe glass fibre subwoofer cone is purpose built for this package, it is lightweight, durable and rigid without compromising sound quality. A lot of market leaders have a generic subwoofer (from their range) then they build a box to suit. Which works to an extent, this package offers you something more unique and performance based . RCA Input Sensitivity 0.2-6V High Level Input Sensitivity 1V Comes with Remote Phase Switch 0-180 Degrees Bass Boost 0dB~+12dB Subsonic Filter 20-Hz-50Hz LPF 50-150Hz T.H.D 88dB Fuse Rating 25A Impedance 4 ohms Dimensions 248x255x250 (MM) Weight: 8kg