Speakers make sound. However, not all sound generated by a speaker is good. The sound we want to hear, the good sound, is the sound that comes off the front of the speaker's drivers, e.g. the tweeter and the woofers. Sound coming off the back of of the drivers bounces around inside the cabinet, builds air pressure and vibrates the cabinet walls. These vibrations, although small, create sound in the room that is distorted and interacts with the good sound. This interaction colors the good sound resulting in a loss of detail and fidelity. One of the great obstacles to overcome in speaker design is the cabinet and it's resistance to vibration and resonance. The more dense and sturdy the speaker's cabinet, the lesscoloration is introduced into the sound that reaches your ears. There are many options for dealing with this but not all options are equal in practicality and economy. B&W's solution for low frequency drivers is the Matrix cabinet. The Matrix design appears throughout B&W's speaker line but its peak incarnation, and its original appearance, resides in the cabinet of the 800 Series speakers. The Matrix is essentially a structure of interlocking cross supports around which the speakers external cabinet is built. These cross supports press against the interior walls of the cabinet at multiple symmetric points which exponentially increase the rigidity of the cabinet. In addition, the three dimensional honeycomb structure creates a series of smaller chambers that significantly reduces the amount of reflection that occurs inside the cabinet. Furthermore, the 800 Series speakers (beginning with the Nautilus 800 Series, instroduced in 1998) have a rounded or lute-shaped cabinet which further reduces sound propagation inside the speaker cabinet by eliminating parallel surfaces.
Compile these attributes and you have a speaker cabinet that behaves more like a block of concrete in terms of rigidity and vibration resistance. The result is sound that remains both pure and powerful as it travels unfettered from the speaker to your ears.