POLK AUDIO PURIST SERIES

Brand

POLK AUDIO

Polk SDA speakers are designed to create a wide sound stage, extending well beyond their physical spacing. The effect requires multiple arrays of drivers and careful control of their phase relations and radiation angles. Not surprisingly, the SDA systems tend to be both large and expensive. In creating the RTA series, Polk’s aim was to utilize the same basic line-source configuration as featured in the SDA systems, with just one of the SL3000 tweeters developed for the most recent SDA systems, to create affordable speakers of moderate size whose sound would surpass that of competitively priced systems. The Polk RTA 15TL is a columnar, floor-standing system measuring 43 inches high, 12-1/2 inches wide, and 15-1/2 inches deep and weighing more than 70 pounds. A vertical array of four 6-1/2-inch bass/midrange drivers, using trilaminate polymer cones, occupies most of the front panel. At their center, on the same vertical line, is the ferro-fluid-cooled trilaminate-dome SL3000 tweeter. An angled “diffraction spoiler” extending upward and forward from the tweeter’s mounting plate breaks up the symmetry of the vertical driver arrangement. The resulting reduced diffraction is said to smooth the response between 2,000 and 10,000 Hz, and Polk claims that it makes audible improvements in imaging as well as frequency response. Below the line array is a 10-inch passive cone radiator that extends the low-bass response of the system. A second passive cone, of the same size but with a different resonant frequency, is located at the bottom of the rear panel. Polk’s specifications for the RTA 15T include a frequency response (between the -3-dB limits) of 27 to 25,000 H