teristics, in addition to applying directivity control. Unfortunately, this version was not a success due to the fact that the drivers were simply too far apart to result in an acceptably constant directivity. The aim of the second prototype, shown in Figure 6 was to abandon the steerable beam concept and concentrate on making an extremely narrow and constant horizontal directivity. The resulting loudspeaker was well-suited to solitary, active listening, as its spatial presentation of recordings was remarkable. However, it was decided that this would not make an appropriate product for Bang & Olufsen due to its focus on a single listening position. Consequently, the aim for the third prototype was to create a hybrid between
the first two - a loudspeaker with the capability of making forward-facing beam with an adjustable horizontal directivity (now called ‘Beam Width Control’), but also the option to change the primary direction of the beam in a wider directivity to one of a small number of directions (or ‘Beam Direction Control’). The result, shown in Figure 7, was a forward-facing cluster of 3 tweeters and 3 midranges, giving the possibility of creating a narrow horizontal directivity. In addition, the side, and rear-facing drivers from Prototype 1 were incorporated to be able to steer the sound beam in either of 4 directions. The configuration of Prototype 3 was almost identical to the final production model. The only difference was that the
single rear-facing midrange and tweeter were replaced by two of each, giving the possibility of a left-back and right-back Beam Direction. The end result is a loudspeaker that can be different loudspeakers for different customers - or can fill different roles in one customer’s home. In narrow-front mode, the Beolab 90 can meet the needs of the most demanding audiophile. However, its other modes (selectable using the included application or automated by audio sources) make the Beolab 90 an extremely adaptable loudspeaker. At the same time, it fulfils the targets set at B&O over 50 years ago - to make a full-range loudspeaker with a constant directivity that fits seamlessly into the customers’ homes and lives. Beam Width Control Disabled 150
Horizontal Angle [°]
100 50 0 −50 −100 −150 100
Fig. 6 S40 prototype 2. The loudspeaker included one rear-facing midrange, tweeter and supertweeter.
Fig. 7 S40 prototype 3 and the first pre-production BeoLab 90.
1000 Frequency [Hz]
10,000
Fig. 8 Directivity of the BeoLab 90 with Beam Width Control disabled (only the front-centre woofer, midrange and tweeter operational). Contours are in steps of 3 dB related to the on-axis response.
Timeline —
1925 Company created
1960 - 1962 The Rondstraler Tweeter (1960-1962) showing the two loudspeaker drivers and reflectors with the grille removed. The intention of this design was to provide an omnidirectional directivity in the horizontal plane to better match the behaviour of the low-frequency section.
52 — The Danish loudspeaker 100 year anniversary
1967 - 1971 Beovox 2500 Tweeter (1967-1971) - another attempt to deliver an omnidirectional high-frequency dispersion, this time in three dimensions. Each face of the cube contains a 50 mm tweeter, all six of which are driven with the same signal.
1976 - 1987 Beovox 120.2 (1983-1988) one of the many ‘Uni-Phase’ loudspeakers with a woofer, tweeter and ‘phase link’ driver.
1978 - 2003 The Beovox CX-series passive loudspeaker. When sales of these ended in 2005, over 570,000 had been produced.