For superb sound reproduction of the ultra low frequencies, this high-grade sub is key. It ensures excellent tone matching with the other RSII speakers. The cone features an optimised blend of pulp materials which greatly increases rigidity, leading to higher linearity. Combined with the integrated centre cap, this sub can reproduce sounds under 50 Hz – transcending its size. The unit features a corrugated surround, which is coated by a damping liquid on the surface and the back side. It guarantees fast and accurate vibration response, and reduces interference between the cone and the edge. The large voice coil drives the cone efficiently, without flexure; the large-sized neodymium magnet manages the coil with power and precision. By utilising the opening at the back, back pressure balance is easily controlled, which perfectly harmonises movement with the cone. So, even the heaviest of bass can be reproduced exactly. The thin enclosure design adds up to system flexibility and easy installation.