Polk RTA-15T
A line-source tower that borrowed the SRS playbook and two 10-inch radiators. Polk's own advertising promised one listen would take your breath away.
Overview
The RTA-15T shows up in old magazine adverts more often than it shows up in the wild. The copy that ran in the audio press tells you what the engineers were chasing. Polk's own advertising billed the RTA-15T as the product of "state-of-the-art technology and superior design," and admitted where the technology came from: the limited-production SRS, or Signature Reference Loudspeaker System. That lineage is the most interesting thing about the speaker. The RTA-15T was conceived as a way to bring SRS-derived thinking into a more conventional floorstanding format.
According to the manufacturer's literature, the core of the design is a line source array. Polk argued that this array "achieves an openness and spaciousness permitting a wide range of optimum listening positions." In plain terms, it is a tall vertical array that behaves less like a point source and more like a curtain of sound, so the sweet spot is wider than a conventional two-way would give you. Whether that holds up on a given pair is a listening-room question, but the intent is clear from the documentation. At the center of that line sits Polk's SL3000 tri-laminate tweeter, which the company described as an engineering triumph in high-frequency smoothness and dispersion. Collectors tend to latch onto the tri-laminate construction. It's the same tweeter family the SRS work leaned on, and it's the part of the RTA-15T that most clearly carries the flagship DNA.
Bass is handled by a pair of 10-inch sub-bass radiators, one on the front baffle and one on the rear. Polk's pitch was that this dual-radiator arrangement "achieves deeper, flatter, more accurate bass than conventional designs." A front/rear passive-radiator pair is a legitimate way to tune low-frequency extension without asking the active woofer to do all the work. The tradeoff, as with any rear-radiator design, is placement sensitivity. The back of the cabinet is doing acoustic work, so shoving the RTA-15T flat against a wall does it no favors.
Finishes, per the period advertising, were natural oak, natural walnut, and black oak wood veneer. The advertising ran across several months and several titles. Audio (August 1990, p.51) carried the same RTA-15T spread that appeared in HiFi-Stereo (July 1990, p.9), and the copy was still turning up in Audio as late as May 1992 (p.51). That's a sustained push, not a one-season experiment.
What the documentation does not give us is the boring-but-essential stuff — sensitivity, nominal impedance, crossover points, cabinet dimensions, weight, original MSRP. None of that appears in the surviving material, and it would be irresponsible to guess. What can be said with confidence is the design intent: an SRS-derived line source, the SL3000 tweeter at its core, dual 10-inch sub-bass radiators front and rear, and a veneer finish in three flavors. For a collector chasing the Polk sound of the early '90s, that's the RTA-15T in a nutshell — a speaker that wears its flagship heritage on its baffle and asks only that you give its rear radiator some air.
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