B&W PV1 active subwoofer

Overview: Price: £950 Website: www.bwspeakers.com Size (WxHxD): 29x34x35cm Weight: 20.5kg Drivers: Twin 200mm reaction-cancelling drivers mounted back-to-back Power: 500 watt integrated power amplifier Inputs: 1 RCA line level, 1 RJ11 Outputs: 1 RCA line level Controls: Volume, low frequency roll-off, phase +/-, high frequency roll-off, on/auto/standby Finishes: Silver with mid grey trim, or gloss black with dark grey trim Plus points: Compact size, unique look, low bass extension for its size and terrifically controlled sound Minus points: Pricey for a mini sub

There are many subwoofers which take the look of a very plain, square box. They're designed to be tucked out of sight, relying on the non-directional nature of bass frequencies to fill a room, without the need for the speaker to be on display. There are other subwoofers which feel no shame in taking some of the limelight, since they're designed to be seen and commented on. The B&W PV1 is most definitely one of those subwoofers.

The PV1 (Pressure Vessel 1) is what happens when one of the most respected speaker manufacturers in the world tells its design team to come up with the best mini sub it can, regardless of cost. In seeking the most rigid enclosure they could create, the engineers at Bowers & Wilkins' Steyning Research Labs came up with the idea of the bathysphere, the spherical diving vessel designed to withstand enormous pressures while exploring the oceans' depths. The sphere, so the thinking goes, is the most efficient natural shape for the containment of air under pressure, and the lack of corners or parallel surfaces incidentally pretty much eliminates the possibility of standing waves and resonances.

So the PV1 was born, though its shape isn't the only thing that makes it different. It features not one, but two 200mm drivers placed back to back, each one facing outwards on opposite sides of the orb. The idea is that they are mechanically balanced, so that any vibration is mirrored by the other driver, so effectively cancelling it out. This virtually eliminates any kind of mechanical vibration which would normally occur, and means that the PV1 doesn't require any spikes or other form of isolation, but can merely rest on the floor atop a small rubber ring, which protects and hides the device's terminal panel.

You'll want to find a good spot for it and leave it there, as its 20.5kg bulk combined with its smooth and generally even bowling ball-sized aluminium alloy enclosure makes it difficult to move around, unless you're feeling cavalier enough to roll it, but at this price we certainly wouldn't advise it. The terminal panel includes a line level input and output and a speaker-level telecoms-type RJ-11 socket (it comes with a suitable cable), plus a two-pin power socket. Also lying flush with the sphere's outer skin is a row of five controls, operated by twisting a coin, and which includes volume, low frequency roll-off, phase +/-, high frequency roll-off, and an on/auto/standby switch.

The drivers use a sandwich construction, with mica composite cone, a polystyrene foam core and a concave outer aluminum skin. They reach virtually to the rim creating a sealed enclosure which is very effective at preventing any internal sound from escaping. There's plenty of power on offer from the built-in 500-watt IcePower digital power amp from B&O. The relatively high power output is necessary to get the low end from such a compact enclosure. It's very good at it too, although there is an option to daisy-chain two or more PV1s together for additional power and scale.

Sound
Like the bathysphere diving vessel that inspired its shape, the PV1 will go low. Very low, down to 18Hz should you require it, though it has a low-pass frequency filter which can be set to any of seven stages between 40-140Hz. This helps when marrying it up with whatever speakers you plan to use, either for stereo or surround listening. The low vibration theory was simply but effectively proved by placing a hand on top of the PV1 while it was playing at loud volume - it revealed virtually no obvious vibration - quite a spooky result from a mini sub.

The long throw, high output drivers combined with the high power output from the internal amp produced results that would be impressive in a subwoofer twice or even three times the size. Trying it with a pair of KEF Q4 standmounts, which are not noted for their bass extension, we found the PV1 delivers a clean, even and precise sound that was noticeably free of coloration. With orchestral music it helped to round out the acoustics of the concert hall, adding a certain depth to the overall feeling of the music. With more bass-heavy dance music it proved that it can get down with the best of them, providing plenty of low-end punch, but, following a spot of experimentation with the filter options, without dominating the sound.

Verdict:

This is a beautiful looking subwoofer which also boasts a wealth of fascinating technology that could well be duplicated in many more devices in the future. Its set-up is versatile, and it should be compatible with virtually any speaker combination while its implementation is highly effective - few, if any, compact subs sound better. Its relatively high price may put it out of the running for many but stylistically, technologically and practically, it's a little marvel.