DESC: Due to their diminutive sizes and single front firing driver design, the SPL Series subwoofers are easily custom installed or hidden in any room. Yet with their classic styling, blue LED and integrated speaker grill, you just might want to show them off. The new SPL subwoofers feature the latest generation of Velodynes patented "ERS" (Energy Recovery System) Class-D digital amplifiers. The ERS amplifiers are over 95% efficient. This gives us incredible power from a very small package. The unbelievable efficiency contributes to cool operating temperatures, reliability and long term operation.