Bowers & Wilkins CM Series CM7 User Manual

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Sharply styled and classily finished, the CM7 introduces B&W’s unique FST driver at a new low price

PRODUCT B&W CM7

TYPE Floorstanding loudspeaker

PRICE £999 per pair

KEY FEATURES Size (WxHxD): 20x91x30cm

P Weight: 20kgP 25mm aluminium dome tweeterP 130mm ‘surroundless’ FST Kevlar cone midrange driverP 165mm paper/Kevlar cone bass driver

P Sensitivity: 88dBP Impedance: 8 ohm (nominal)

CONTACT 01903 221500q www.bwspeakers.com

As the world leader inhi-filoudspeakers,Worthing-basedB&W has been particularly

adept at finding and/or creating niche-fillingmodels at a wide variety of prices. The company has a dozen different series of models covering every conceivable price, size and style. TheCM-seriesmodels are relatively recent arrivals on the scene, initially filling a gap between thevinyl-covered,budget-price600-seriesand a more stylish and technically advancedCDM-NTSeries, essentially by combining the engineering of the former with thereal-woodveneer of the latter. Recently though, things have become rather more complicated. Themid-priceCDM-NTsare no more, replaced by the700-seriesand a wholly new slimlinemetal-jacketXT-serieslaunched at around the same price. The two new latest introductions from B&W are in this intermediaryCM-series;both sit in the gap between the 600s and the 700/XTs, but they’re rather more than just prettied up 600s. They do have the attractive real wood finish, but they also borrow some of technologies from the 700/XTs. This was not particularly evident in the littletwo-wayCM1 miniature, which we reviewed inHFC 277 andHFC 279, but it’s far more obvious in thisthree-wayfloorstanding CM7. Although its £999 per pair price tag is substantial, this is also the first time that the company’s radical FST midrange driver has been available at such a low price. This unique feature demands proper explanation.

The FST (Fixed Suspension Transducer) is a special type of midrange driver, which

B&W engineers originally pioneered in the much more upmarket Nautilus models. Its particular distinguishing factor is its replacement of the usual type of flexible surround attached to the edge of the cone diaphragm by a polymer ring. This ring is in contact with, but not physically attached to,

the cone edge.

The logic is impeccable. In the majority of three-waydesigns, the midrange driver is either the same as (or a scaled down version of) a bass driver. But the difference between amidrange-onlydrive unit and a driver required to produce bass (with or without midrange) is that a bass unit needs to allow significant fore’n’aft excursion, and this factor is quite unnecessary in amidrange-onlydriver. Whereas the multiple roles of the conventional rubber roll surround include centering the cone, absorbingedge-of-cone

vibratio and permitting generous fore’n’aft excursion, by omitting the last of these, B&W engineers have designed a cone termination specifically oriented towards optimising the vibration absorption characteristics, by using a heavy rubber gasket in place of the usual roll. The alleged consequence is a significant improvement in dynamic range resolution.

The attractive sharp-edgedcabinet, made in B&W’s Danish factory, comes finished in wenge, rosenut or maplereal-woodveneers. Our rosenut samples lacked any real grain and therefore weren’t the most convincing, it must be said (but then neither is the concept of a rosenut tree). But the end result is at least marginally preferable to vinyl woodprint.

To avoid lugs, magnets hidden beneath the veneer hold the fabric grille in place, and all three drivers are flush-mounted.Matching the shiny trim around the other two units, the tweeter’s highly polished faceplate is partly cut away to allow it to be located as close to the midrange unit as possible. The tweeter is fitted conventionally into the front of the enclosure, not externally which is B&W’s favoured approach, but it does use an internalNautilus-stylerear loading tube. The 25mm alloy

dome gives output right up to 50kHz and also has a low enough resonance to allow a first-order,single capacitor network.

REPRINTED FROM november 2006

B&WCM7loudspeaker [Review]

“Atthesametime,theCM7offersclear advantagesoversmallertwo-waydesigns,throughthedelicacyofitsmidandtopend.”

Helping to keep the cabinet slim, the CM7’s FST midrange driver is smaller than the versions used in B&W’s more upmarket models, though its Kevlar cone still has the same 120mm diameter as the paper cone used in the nominally larger bass unit.

Twin terminal pairs offer the bi-wire/bi-ampoption, and a generous flared Flowport at the rearreflex-loadsthe enclosure. A hollow foam port sleeve offers an interesting port tuning option. Floor coupling is achieved via 6mm spikes (with a rubber foot option), and these fit directly into the base. While the speaker feels stable enough, one can’t help feeling that a separate plinth, for aesthetic as well as stability reasons, ought to be part of a £1,000 package.

SOUND QUALITY

Work started with the speakers located clear of walls, and connected up to a system using a Naim CDS 555 CD player, Rega P9/Naim ARO/Rega Apheta record player, Magnum Dynalab MD106T FM tuner and Naim NAC552/NAP 500 amplification, plus Vertex AQ and Naim cables.

Having spent the previous day listening to a pair of B&W’s massive and costly 800Ds, it was hardly surprising that the first impression of the CM7 was a little disappointing. This much more modest model lacks the scale, authority and also the subtlety of its big brother – but such a comparison is distinctly unfair, given the 13:1 difference in price.

A few hours acclimatisation usually allows one to adjust to the inevitable shifts in tonal balance that occurs when changing speakers. But by the following day, the CM7s still weren’t getting this reviewer excited. The top end seemed sweet and encouraging enough, but the music as a whole was sounding thick.

The in-roommeasurements provided the clue, as the whole bass region, especially around the 45Hzport-tuningfrequency, was clearly dominant over the midband. Happily, the solution – inserting those hollow bungs – turned out to be simplicity itself. These not only damp the port output somewhat, they also shift its tuned frequency downward to around 30Hz. This has a dramatic effect on both the measured and the perceived tonal balance of the speaker, and the effect is totally positive. The complete removal of that bass heaviness and thickening immediately brought a natural tonality to orchestral music, and made it much easier to hear the impressive qualities of that special midrange driver. Male voices no longer had a thick and chesty quality and the speaker as a whole seemed altogether more transparent, with much improved stereo image perspectives. Initial fears that B&W had got this one wrong were entirely laid at rest.

The CM7 has its limitations, for sure. But that’s true of any £1,000 loudspeaker...

otherwise there’d be no sense in making an 800D. The CM7 falls short of ultimate performance, but the crucial point is that it

does so evenly, and delivers a well balanced all-roundperformance in every respect. One might wish for more of the dynamic drama and smoothness that larger and more costly speakers provide. But you’ll be wishing for the same from any speaker at the CM7’s price. At the same time, the CM7 offers clear advantages over smallertwo-waydesigns, through the delicacy of its mid and top end, and a bass delivery that’s deep and crisp and even. Indeed, with bungs in place the bass

extension is a creditable 24Hz for -6dBunder ourin-roomfar-fieldconditions, alongside decent 88dB sensitivity, even if the load has afour-ohmminimum at 140Hz.

The bottom line is that the CM7 is a fine all-rounderin both appearance and sonic performance. But don’t ignore those clever hollow bungs, as inserting them made all the difference under our conditions.HFC

Paul Messenger

 

VERDICT

 

 

 

SOUND >> 85%

R PRO

 

 

 

 

 

 

 

 

 

 

 

 

Afineall-roundperformer,

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

withgooddynamicrange,a

EASE OF DRIVE >> 80%

sweettopend,lowenclosure

colorationandanexpressive

 

 

 

 

 

 

 

 

 

 

 

 

midband.Aneasyspeakerto

 

 

 

 

 

 

 

 

 

 

 

 

like,physicallyandsonically.

BUILD >> 87%

 

S CON

 

 

 

 

 

 

 

 

 

 

 

 

Soundssmallandlackingin

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

scale,weightanddynamic

VALUE >> 86%

expression.Real-woodfinish

lacksconviction,andtheneed

 

 

 

 

 

 

 

 

 

 

 

 

foraproperplinthisobvious.

 

 

 

 

 

 

 

 

 

 

 

 

 

CONCLUSION

Withthecleverbungsinplace,theCM7deliversafineoverall balancewithgooddynamicrangeandasweettopend,froman attractivelycompactunit.Thesoundcouldperhapshavemore scaleandexpression,butatthepriceit’sagoodall-rounder.

OVERALL SCORE >>86%

REPRINTED FROM november 2006