The IS1218 is a dual high power subwoofer system comprised of a single 18-inch woofer. This IS1218 can be clustered in the same fashion as the 2-way models. Many eyebolt suspension points have been provided for easy flying. The new installation series speakers address a number of important issues that give them unprecedented performance and handling characteristics for live sound applications, including permanent installations. In particular, phase characteristics have been kept smooth and consistent throughout the entire series, so you can mix and match speakers to suit any system and venue without ending up with hot and dead spots due to phase interference. And of course sonic quality is superb throughout the entire reproduction range so the full impact of the source material reaches the audience undiluted. This approach to design is evident in every Yamaha commercial audio product. The proof is in the enormous success of our groundbreaking PM1D and PM5D digital consoles, digital signal processing products and industry-standard analog live consoles and related gear. Yamaha is simply dedicated to delivering the best sonic performance available anywhere, at any price, from system input to output. Our new installation series breaks new ground once again with performance and convenience that can take the sound at any venue to a higher level.