What is an FMOD? The FMOD is an active crossover simulator. It is better than a much more expensive electronic crossover that requires power to operate. FMODs are packaged in pairs and can be combined with other FMODs to obtain bandpass ranges or with other types of crossovers to change the slope and crossover frequency point. FMODs feature a 12 dB per octave crossover slope and are compatible with all RCA type input amps...simply place the FMOD in-line with the patch cable running between the source (head unit) and the amplifier. 24kt gold over brass construction, 10 volts maximum RMS input. One-year manfacturer warranty. Made in the U.S.A.