Bowers & Wilkins PM1 Loudspeakers (Hi-Fi+)

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B&W Group PM1
Bowers & Wilkins PM1 Loudspeakers (Hi-Fi+)

With its Nautilus tubed tweeter cradled on the top and shiny livery, this compact standmount looks distinctly like a miniature 800 series design, an 808 perhaps. But the PM1 shares only one component with its more expensive brethren; the cable terminal core. The influence however is very clear, it’s the first non-800 series model to feature Matrix internal bracing and both the housing and construction of the tweeter are based on the same design theory. There are also two rather than four magnets in the motor, even if the dome is not diamond but more affordable carbon braced aluminium. This has 40kHz break-up which is still some way below the 70kHz of diamond but a useful 10kHz higher than aluminium alone.

These figures might not sound all that impressive but they are crucial if you want to the speaker to be able to produce natural sounding high frequencies. Even though these break-up points are beyond the human hearing range what happens to the sound above this point has an effect in the audio-band, much like they way that higher sampling rates give greater treble extension which results in cleaner midband. The two are not unrelated of course, it was not necessary to make tweeters that rolled off smoothly in the analogue era because vinyl rolled off first. With high-res music files, we have material that theoretically goes up to 96kHz and anyone who has heard a good example of this on a revealing system will know that it sounds more open and relaxed than CD ever did.

Bowers & Wilkins has apparently been using strands of carbon fibre to stiffen the ‘skirt’ or base of 800 series tweeters since the mid nineties, but that process was painstaking and, now they tell us, not terribly stiff because it wasn’t possible to apply thicker strands. With the PM1, the company has used pitch based carbon fibre that is wound into precision rings that fit inside the dome and are extremely stiff, importantly they are also relatively affordable by comparison with the previous system.

The PM1 is quite a dinky speaker; it stands a mere 13 inches high but is densely packed. You don’t expect it to weigh over 9kgs, but this is immediately apparent when it needs moving. It also looks great thanks to the combination of a matt black centre panel that curves down to the front baffle, and very shiny side cheeks in what’s described as Mocha Gloss. This looks great with the matching stand, itself a particularly attractive example of the breed. The base is piano black, with metal discs denoting the spike positions, and fluting on the single column to give it a more elegant appearance. It is inevitably quite expensive for a stand, but is well made and – being wooden – avoids the potential to ring inherent in metal tubing. The stand even has a conduit for cables to minimise the dangle factor and keeps the speaker looking clean.

The main driver is a Kevlar cone in a 130mm chassis that is differentiated from every other mid/bass unit in the catalogue by having a foam bung, rather than a phase plug, at its centre. This is separate to the cone this polymer foam dome acts like a dust cap but without the tendency for such things to act like a whizzer cone. Rather it absorbs energy and reduces cone break up in the process, it looks like the sort of thing that should be appearing on two-way designs the world over, if it works with cone materials other than Kevlar.

The cabinet is not just good looking it’s sculpted form is the work of industrial designers Native and is intended to emulate the shape of the 800 series ‘head’, removing sharp edges so that dispersion is smooth and imaging thus improved.

It consists of a thermoset polymer exterior attached to the MDF interior with a ‘lossy compound’ to form a low resonance cabinet. Boxes of this size are intrinsically easier to control and tend to produce better imaging as a result but it doesn’t do any harm to try and improve matters further.

The stand is supplied with bolts intended to mate it with the threaded inserts on the PM1’s base but the guys in R&D use a sonically superior fixing, namely Blu-tack, so I followed this lead when setting up. As this is a none too sensitive speaker they also recommend a fairly powerful amplifier, so I brought in a Leema Tucana which although an integrated has no shortage of grip, certainly more than its 150 watt rating would suggest. This proved to be a good match, distinctly better than the more refined 50 watt Valvet A3.5 monoblocks usually employed. The extra power allowed the soundstage to expand and breathe in a wholly more convincing and engaging fashion. Steve Pearce from Bowers & Wilkins’ R&D department also recommends placing the PM1s wide apart with their axis crossed in front of the listener, which is usually a good way of creating a broad sweet spot if not necessarily the deepest imaging. He also admitted that they have a slight bump in the low frequency response to make up for their diminutive size and while this is not obvious the speaker does have rather more bass grunt than it rightfully should. With this much resolution and extension available in the treble you need decent bass extension to balance it; a purist might disagree but there are very few compact speakers that don’t take this approach to some degree.

Despite the 84dB sensitivity the PM1s like to play at high level. This is a trait of the 800 series as well and reflects the way that the engineers listen! You hear more when you are refining the product this way and you hear more in the home. They soak up power with minimal effort and deliver a full-scale soundstage without even trying. That small cabinet just disappears to leave the music in the room, Joni Mitchell’s live rendition of “Edith and the Kingpin” on Shadows and Light takes over and lets her voice beguile you. In fact the more voices you play they clearer it becomes that the PM1 is uncannily good at the job of placing them in the here and now. This is presumably related to the high break up of the tweeter delivering a cleaner midband, that and the quality of engineering delivering very low distortion across the board. Distortion on the record is delivered with precision of course; Tommy Bolin’s guitar is searing on Billy Cobham’s masterpiece Spectrum – you want white heat, you got it.

The PM1 is a very revealing reviewing tool as well, easily differentiating between interconnects and making the most of hi-res material decoded by a Metrum Octave DAC. This made for highly compelling listening with familiar material, the speakers easily up to exposing the speed that this little converter is capable of and revelling in the musical treats it unravels.

The Resolution Audio Cantata DAC delivers more of the space and the acoustic detail in recordings, a lot more, and this leads to seriously three dimensional image projection from the speakers. It’s more of a visual experience and one that the PM1 is equally capable of transducing, it allows the character of double bass to escape the box completely and make its presence known in the room without bloom or excess. This particular instrument was played by Dave Holland on the Anouar Brahem album Thimar, an ECM production that lets you hear plenty of tonal depth and nuance of playing when its delivered with this degree of transparency. The space between instruments and the solidity of the notes is first class. If however you enjoy the visceral groove of Led Zeppelin, and let’s face it who doesn’t (!), this is also very much on the menu. I had some difficulty restraining myself when I put the live version of Immigrant Song on at full tilt, and am mighty glad that more of this phenomenal live output has been committed to disc than was available back in the day.

PMC delivered its latest standmount the twenty.22 while the PM1 was in the house and as it’s very close in price makes an interesting comparison. It’s not close in size however, internal volume must be easily double but surprisingly it does not have such meaty bass, rather it excels in openness and pace. The Bowers & Wilkins has a more conventional presentation because it is a reflex ported system rather than a variation on the transmission line theme. Its smaller cabinet means it’s also better able to remove itself from the equation and produce the full-scale drama that well produced material is capable of.

The PM1 is proof that good things often come in small (densely packed) packages. It combines first class timing, spectacular imaging and remarkable bandwidth in a highly coherent and musically rewarding fashion. You need a decent amount of high quality power to hear what it’s capable of but that done you’ll be hard pressed to find a more revealing and engaging super mini. If ever there was a more perfect audio example of the phrase ‘don’t judge a book by it’s cover’ than the deceptively powerful sounding PM1, I’d be surprised.

TECHNICAL SPECIFICATIONS

Features: Nautilus tube loaded tweeter with carbon fibre reinforced aluminium dome, Kevlar brand fibre cone bass/midrange, and Flowport technology.
Type: 2-way vented-box system
Drive units: 1x ø25mm (1 in) reinforced aluminium dome high-frequency 1x ø130mm (5 in) woven Kevlar cone bass/midrange
Sensitivity: 84dB spl (2.83V, 1m)
Nominal impedance: 8Ω (minimum 5.1Ω)
Crossover frequency: 4kHz
Recommended amplifier power: 30W–100W into 8Ω on unclipped programme
Dimensions (H x W x D): 331mm (13in) x 191mm (7.5in) 250mm (9.8in) cabinet only, 293mm (11.5in) including grilles and terminals
Net weight: 9.3kg (20.5lb)
Finishes: Real wood veneers Mocha Gloss
Price: PM1 £1,995; stand £400

Manufacturer: Bowers & Wilkins
URL: www.bowers-wilkins.co.uk
Tel: 01903 221800

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