4" 25/70/100V 2-WAY PANCAKE POWERED BY SONIC VORTEXPerforms great as a combo audio speaker and paging speaker. Our Sonic Vortex technology generates rich, deep bass and effortless clarity from what most people would call a 'back box', but is not. It is actually a compact, integrated tuned enclosure. This patented technology is a 'twist' on Ported Transmission Line design, that optimizes air movement to produce astonishing sound. The enclosure also keeps sound from bleeding to other rooms while adding 6 to 9dB boost in mid-lower bass. Designed to play in full range mode only. Versatile - both round and square grilles included.