Resonances in the body of an instrument such as a violin are an essential part of defining its character. There, the skill of the designer is engineering the resonances to support each note in the instrument’s range evenly. The opposite is true of a loudspeaker. Resonances in its body or cabinet only serve to make the speaker’s character superimpose itself on that of the music it is there to portray. Bracing is an essential tool in keeping the ‘loud speaking’ to the drivers, not the cabinet, so the original character of the instruments can come through cleanly.
Unique to Bowers & Wilkins, Matrix™ interlocking panels take cabinet bracing to the ultimate level. With powerful bass drivers trying to shake the cabinet and high air pressures inside trying to make the panels flex and blur the sound, this three-dimensional honeycomb structure reinforces the cabinet at small intervals and in every direction. Offering a dramatic cut in the level of cabinet coloration, Matrix allows you to focus on where the performers are, rather than being aware of where the speakers are.
Cabinet panel vibration can be a significant cause of sound coloration. Even though the amplitude of the vibrations is small, the large radiating area means that the sound output from the panels is significant and adds a bloom to the overall character. There are two main techniques used to reduce cabinet coloration: damping and bracing. The adding of damping panels to the inside of the enclosure walls, usually in the form of bituminous pads, does much to reduce resonance hangover, but not much to reduce panel flexing while still being excited by the driver. The flexing is non-linear and the distorted harmonic structure of the total output from the speaker changes the timbre of the sound. Stiffening of the panels reduces the amplitude of flexing and this can be done by a combination of increasing the panel thickness and bracing.
Matrix is an interlocking grid of panels arranged in two orthogonal planes, rather like a bottle crate. It is easily the most effective method yet devised of bracing a cabinet. The thickness and spacing of the panels can readily be altered, depending on the frequency range of interest and the panels are perforated acoustically to connect the individual cells and allow the driver to see the whole volume inside the cabinet. To prevent resonances in and Helmholtz tuning between the cells, each cell is filled with absorbent wadding, usually open-cell foam. Matrix was developed by and remains exclusive to Bowers & Wilkins.
Find out what Bowers & Wilkins customers and audio enthusiasts are talking about on our blogs, and read in-depth articles in the Sound Lab.
Production Notes: ‘Saving the Tapes’April 26,2015
Will Gregory in conversationApril 21,2015