Beolab Penta

Beolab Penta was the first B&O loudspeaker to include a built-in power amplifier. Later on this would become the norm, but at the time models such as the Beovox S 80.2, in splendid rectangular teak boxes, were still in the catalogue, and so the Beolab Penta looked radical indeed. At the base of the Beolab Penta was the Beolab 150 amplifier, which is described separately elsewhere. The loudspeaker unit itself was also available on its own as the Beovox Penta, but it is as a single model that both the units were best known and most often seen. Text copyright © Beocentral. Unauthorised reproduction prohibited.

The loudspeaker unit contained a total of 9 drivers and two reflex ports, the largest number fitted to any B&O loudspeaker. The layout was symmetrical, with the bass ports outermost, followed by two groups of two woofers. The 4 midrange units (wired in two sets, the two outer ones and the two inner ones receiving slightly different signals) and the single tweeter were mounted in a separate bay in the centre, and all the loudspeakers were fed from a very complex passive crossover/phase corrector network. It is important to understand the no Penta loudspeaker was ever truly “active”, as is often claimed. An active loudspeaker in B&O terms refers to a model where the crossover takes the form of an electronic filter and separate power amplifiers feed each group of drivers. The Beolab 2500 was the first model offered to work like this, but the technique was really popularised by the Beolab 8000. Text copyright © Beocentral. Unauthorised reproduction prohibited.

Beolab Penta also included a display, which showed which source was playing and the volume level. An “auto limit” indicator was also fitted to show that distortion had been identified and was being surpressed. Easily dismissed as a silly gimmick, the displays were very useful in the context of a linked room in a Beolink system, where of course, as the volume could be set independently, amplified loudspeakers were at their most useful. Text copyright © Beocentral. Unauthorised reproduction prohibited.

The pentagonal cabinets were made of a similar resin that the fronts of the “Uniphase” loudspeakers had been moulded in. The pentagonal section was claimed to offer an acoustic advantage as there were no parallel opposing faces inside, aiding in the damping of internal reflections. The outsides were clad in stainless steel, polished to a soft sheen. This finish reflected the colours of the surroundings whilst not reflecting the image of any specific object, helping the large loudspeakers to blend in. Whilst even this could not make them disappear, they certainly were not the eyesore that some large loudspeakers could be. B&O claimed that the Beolab Penta could provide undiminished performance regardless of placement, and where this true it would have been a genuine breakthrough in loudspeaker design. What the claim in fact referred to was the “bass extension” switch fitted to the Beolab 150 amplifier, which when used with the Penta loudspeaker compensated for positioning in a corner, against a wall or in free space. Excellent stereo imaging was also claimed, due in no small part to the tweeter and midrange drivers being more or less at ear-height for a seated listener. Text copyright © Beocentral. Unauthorised reproduction prohibited.

Beolab Penta proved to be a really strong seller, and was often teamed with the Beosystem 5500 or the Beocenter 9000. The high price was offset by its elegant appearance and excellent performance, though despite this it was largely ignored by the wider Hi-Fi community. The Beolab Penta was replaced by the Beolab Penta 2 in 1990. Text copyright © Beocentral. Unauthorised reproduction prohibited.