Powered sub woofer. Installed New 10" Pyle woofer foam surround (large magnet design, upgraded part). Added felt dampening blanket for improved bass. Replaced (4) 16v caps @ zener diodes. Modified amp circuit for lower noise, most caps updated. Older rugged standard circuit design type. RCA & speaker inputs, frequency/Phase & Level controls. #8+ condition. 17" cube design all black cab, black knit grill, no auto off circuit.