At the heart of the 1528 series lies the Røst Reference Acoustic Core. An advanced waveguide and midrange assembly engineered for controlled dispersion, phase coherence, and seamless driver integration. 

The assembly is built around an elliptically shaped waveguide, designed to position the tweeter and midrange as close together as physically possible. This minimizes vertical lobing and ensures smooth, consistent vertical dispersion, resulting in a larger and more stable soundstage. 

The waveguide geometry is carefully optimized to maintain a broad listening window, even in the highest frequencies. A lens placed in front of the tweeter further enhances performance by increasing sensitivity and reducing distortion in the critical 7–15 kHz range, while also improving off-axis response. At the same time, it serves as protection for the tweeter dome. 

For mechanical stability, the entire waveguide structure is mounted directly to a thick threaded steel plate. This provides the necessary rigidity to properly support the midrange driver, whose oversized motor assembly requires a mounting solution far more robust than conventional wood inserts. The result is an exceptionally solid acoustic core with both structural integrity and acoustic precision.