Yamaha's policy of always putting sound quality first, combined with decades of experience in producing fine speakers, ensures that the sound of these speakers is superior to that of many other in-ceiling speakers. The NS-IC800, NS-IC600 and NS-ICS600 use a blue PP (polypropylene) mica cone woofer and fluid-cooled soft- dome swivel tweeter in a coaxial design. The tweeter swivels so it can be aimed for most effective high frequency output. The NS-IC400 features a Yamaha original double-layer cone that delivers very natural sound tonality. A unique ridge-shape aluminum center cap with a stepped speaker surround eliminates mid-high frequency peaks, so the sound is delivered smoothly and musically.