The "linearisation and protection circuit“ (LPC) is used in all of our active subwoofers. This special filter circuit performs two different important functions: First of all, it effectively protects the subwoofer against subsonic (i.e. inaudible) frequencies that could otherwise cause damage to the loudspeaker. Secondly, this releases power reserves that would otherwise be lost and which the subwoofer exploits for deep bass reproduction in the audible range. The result: A distinctly more linear frequency response and clean, powerful bass.