For many, many years there has been a particularly honoured place in the high fidelity world for reasonably compact, very high quality loudspeakers. They may be limited in bass, but somehow they can offer a presence, a reality to the sound, beyond the capabilities of nearly all large loudspeakers.
Spoiler alert! Our review, below, shall show that the Bowers & Wilkins CM6 S2 stereo loudspeakers are firmly placed in this tradition.
The CM6 S2 speakers are, as implied, fairly compact units. They stand 403mm tall, including the tweeters, which have their own little housing atop the main enclosures.
B&W’s CM range consists of two models with the stand-out tweeter, the remainder without. Those with the top-mounted tweeters seem to be positioned as the premium models within a premium range. The CM6 S2 (the S2 means Series 2, for these are a significant upgrade from the original CM range) actually has largely similar specifications to the less expensive CM5 S2, which has the tweeter relatively conventionally located within the main enclosure. The main reason for top-mounting the tweeter to increase the decoupling of the tweeter from the bass/midrange driver and the enclosure.
The tweeter sports a 25mm aluminium dome. Its teardrop-shaped enclosure is attached somewhat flexibly to the main enclosure. Much of the main box’s vibrations ought to be damped and thereby unable to affect the sound emanating from the tweeter. Of course it incorporates a number of technologies developed by B&W for its ultra-high-end Nautilus speakers.
The bass/midrange driver is a 165mm Kevlar cone unit. B&W specifies the frequency response of the loudspeaker from 50 to 28,000Hz ±3dB, and puts the -6dB points at 45 and 50,000Hz. It says that the reference response (i.e. the ±3dB figures) are accurate to within 2dB even off-axis, up to 60 degrees horizontally and 10 degrees vertically. Second and third harmonic distortion components are specified to be less than 1% for output between 100 and 22,000Hz, 90dB in level at one metre, and less than half a per cent between 150 and 20,000Hz. These figures are impressive when you consider that most speaker makers shy away from mentioning distortion levels at all.
The rear of the unit features a large bass reflex port with B&W’s distinctive golf-ball like dimpling (it’s called ‘Flowport’), plus two pairs of gold-plated binding posts to allow bi-wiring.
The review loudspeakers were gorgeously-finished in piano gloss black. Rosenut, shown here, and white (overleaf) are also available.
The imaging, the soundstage, produced by these speakers was truly something to experience. After a couple of days of playing random music at various levels of volume and of varying levels of complexity and tonal balance to make sure they were run in (we were assured that this had already been largely done by the supplier), we sat down for some serious listening.
We’d already had hints of something special on the imaging front, so we began with the album ‘Pornograffiti’ by Extreme, a strange and varied piece of work. While the album is largely metallish, the track ‘When I First Kissed You’ is a love song in lounge-bar style, delivered cleanly and close to mono in its lack of spread, except for the imposed vinyl clicks (we listened from CD). The precision of the mono image was startling. There could have as well been a single high quality speaker centred between the CM6s. The double bass accompaniment was superb, tight and with a coherence that conjured the sense of the instrument’s actual presence in the room. The vocals had a zing suggestive of the use of a live-style vocal microphone. But while making this clear, the speakers held it to just this side of sibilance.
‘He Man Woman Hater’ from the same album starts with an insect that flies around the room. Or it does if the phase coherence and channel matching of the loudspeakers is up to the task. These speakers clearly are, just about enough to bring one to flinch as the virtual bee flies too close to the listener.
But things could get even better. We put on the track ‘Nobody’ from Ry Cooder’s album ‘Jazz’ and we felt the wide stage spread was a touch narrower than we expected. We tweaked the speaker positions a little, sliding them a touch further apart so that they and us formed the three corners of a true equilateral triangle. Pointing them directly at the prime listening position was optimal. They don’t need spurious high frequency peaks to be tamed. Their smooth, controlled delivery is clearly intended to be made available to the listeners, not disguised by off-centre placement. Since we had them a good metre from the rear wall, there was no need to use foam bungs in the ports (B&W as usual provides these).
With this positioning the soundstage opened up to full width (which was somewhat wider than the limits imposed by the speaker locations), while each voice and each instrument in the track occupied its proper position, not only from left to right but also from front to rear.
Time and again, track after track, there was a solidity and seeming existence of musical elements that was quite breathtaking.
In large part that must be put down to the physical separateness of the tweeter on these speakers. But midrange detail was just as impressive, and the ability of the speakers to absorb power was even more impressive. Why link those two attributes together? Because as we advanced the volume control, the speakers held the sound together in a way that is most rare. Rather than collapsing into incoherence, the clarity of sound remained at remarkably high levels. We used a high quality 250W per channel stereo amplifier, so of course we had plenty of power on tap.
But there are limits. In particular, while the CM6 speakers made a good show of bass, with excellent balance and articulation down to somewhere below 50Hz, there was a sense with familiar bass-underpinned music that the gut-thump of the 30 to 40Hz range was absent. On ‘Take the Power Back’ on Rage Against the Machine’s self-titled album, that absence was particularly noticeable. Yet... yet... even on this track there were compensations. The dynamic change around 4:40 in, where the coda commences with a delicate ringing of the cymbals was spine-tingling in its delivery, and when we threw caution to the wind, along with any consideration of our neighbours, and turned the music up to a ridiculous level, the power and poise exhibited by the loudspeakers made us think that perhaps we were being churlish in our bass expectations.
We hasten to add that a bass limitation does not necessarily mean a loss of impact. Putting on our favourite rendition of Schtschedrin’s 1960s ballet orchestration of Bizet’s ‘Carmen’, the percussion-heavy dynamism of the performance was astonishing, and absent of even the slightest hint of volume compression. This was nothing short of a thrill.
Bringing things down to a more intimate level, Laura Marling’s ‘Once I Was An Eagle’ was tamed of its close-miked sibilance, shining with her up-front delivery, the delicate delivery of her guitar, and the other instruments layered through the depth of the stage.
We ran a measurement of the speakers’ sensitivity and it came in — using our fairly stringent test (we use 500-2000Hz bandwidth limited pink noise) — at 86dB at 1 metre for 2.83 volts average.
We don’t normally mention this because our measurement microphone isn’t rated for accurate performance in the ultrasonic ranges, but it can give an indication of reach. Using a 96kHz pink noise signal, the output turned out to be strong all the way to 36,000Hz. The tweeter truly is a ‘super tweeter’, at least in terms of high frequency extension.
The main reason we measured was to check out bass extension.
Up close to the woofer’s cone (to overcome room effects), the output started to roll off gently around 110Hz, to be six decibels down at 73Hz. But measuring close to the port to determine its contribution, its output increased by six decibels over the same range and peaked at around 60Hz, maintaining that output down to 50Hz, falling away at a little above 12dB/octave below that. Combined, it pretty much perfectly matched B&W’s specifications.
The Bowers & Wilkins CM6 S2 loudspeakers fit firmly into that tradition of high quality compacts, delivering a startlingly realistic performance, one so convincing that occasionally we shivered with the sheer excitement of it all!
+ Wonderful presence; Smooth and well balanced; Capable of startling output levels
- Best with plenty of power available; Perhaps could do with a few more hertz at the bass end
Drivers: 1 x 25mm aluminium dome tweeter, 1 x 165mm Kevlar cone bass/midrange
Frequency response: 50-28kHz ±3dB; 45-50kHz -6dB
Impedance: 8 ohms (min 3.7)
Sensitivity: 88dB (2.83V/1m)
Power handling: 30-120 watts unclipped (recommended amplifier power)
Cabinet: Bass reflex (rear port)
Dimensions (hwd): 403 x 200 x 285mm
Weight (each): 8.9kg
Warranty: Five years
Distributor: Convoy International