CKS ACOUSTICS CTB 118B 18″ Passive Subwoofer. CTB 118B 18″ Passive Subwoofer features a professional band-pass design that delivers class-leading output and deep, room-filling lows. With tons of power and a high-output/deep punch band-pass design, the CTB 118B is the perfect subwoofer to complete your professional PA. CB 118B subwoofer extends the hass response of virtually any full range speaker, relieving that speaker of the difficult task of having to reproduce the low bass frequencies. A system with stunning wide-range response characterized by dramatic, impactful low frequencies and effortless, undistorted mids and highs. The listening audience will hear everything with perfect clarity, from the lowest bass synth tones to the highest percussion bells and everything in between.