Polk Audio RTI A9 Black Floor-Standing Speaker - The new RTI A series feature several upgrades. From the incorporation of our latest Dynamic Balance Cone drivers and 1 inch tweeters to an elegant restyling of the cabinets in keeping with the latest styles. The floor-standing models feature "Power Port Plus" an enhancement of Polk"s patented Power Port technology. As you would expect from this highly popular line, the performance is classic Polk.