Philips Sound Purification Duct (SPD) bass port technology delivers the deep, pure tones of the original bass sound. Using an SPD foam material to process the inner surface of the bass pipe, the special acoustic damping invented by Philips reduces noise turbulence and stabilises the tuning frequency. Philips technical and consumer tests confirm this buffer provides less coloured, purer quality bass.

With its box-within-a-box design, this band pass subwoofer has two volume chambers to create more air capacity and deliver an altogether better bass sound with better balance and less distortion. The audio energy from the central driver is concentrated more effectively in the desired frequency output range, producing an overall sound image that is more focused and more accurately reproduced.

A single speaker driver normally incurs a specific frequency division vibration near the edge of the diaphragm, often resulting in some sound distortion. The way to overcome this problem is by using Mylar, a uniform monomer and a much lighter material that is more usually used, around the driver cone. Surrounding the cone in a perfectly symmetrical ring, the resulting damping effect suppresses the asynchronous vibration, resulting in a more balanced and natural sound.