Having busied itself to good effect in developing its flagship Nautilus 800 Series of professional monitors, B&W's research and development team has now gone on to revamp its mainstream DM600 Series. The good news for potential purchasers of any of the new DM600 S2 (Series 2) models is that many of the Nautilus innovative design features have been incorporated without any upping of the price.

The DM603 S2 (£549.95) reviewed here is the smallest of three floor-standing models, measuring 850 x 236 x 306mm, with two 180mm drivers (one bass only and one bass/midrange) and a 26mm tweeter. The aluminium dome tweeter is a new design employing a Nautilus style tapered tube at the back to absorb unwanted rear-radiated energy while damping the unit's main resonance and lowering coloration. A flat ring suspension is designed to yield less distortion than the usual roll surround and both sensitivity and off-axis response have been improved.

Frequencies below the 4kHz crossover point are handled by two 180mm units, as already mentioned. First comes a woven Kevlar cone driver, in that golden/ yellow colour which has been a B&W feature for many years, with the mixture of resins and damping compounds configured for an unusual 'octopole' bell mode break-up action which promotes cancellation of unwanted harmonics. A stiff spider, combined with a bullet-shaped dustcap, gives improved control of bass. The second woofer comes in at around 150Hz and is designed to combine lightness with rigidity. It has a reinforced paper cone with a large mushroom-shaped dustcap attached directly to the specially extended voice coil.

Each bass/mid-range driver has its own reflex enclosure, the upper unit being ported to the rear and the lower having an oval-shaped port at the front. High quality crossover components include aircored inductors and plastic film capacitors. The slim-line enclosure is finished in either cherrywood or black ash vinyl veneer. The front baffle board is strengthened by a second baffle of dark grey moulded, mica-filled polypropylene with rounded edges.

This contouring of the perimeter is intended to diminish diffraction effects and is continued on the moulded plastics grille frame which extends from top to bottom, with a small recess at the top for the B&W insignia. A fairly large recess near the bottom of the rear panel accommodates two pairs of well-spaced gold-plated terminals. Plated metal shorting strips are provided to allow either single or bi-wire connections.

Perhaps responding to comments made from time to time by fellow reviewer Geoffrey Horn, the designers supply two pairs of plastics foam bungs with different porosities which can be pushed into the reflex ports. These are meant to fine tune the extreme bass and can, for example, optimize the response for differing loudspeaker-to-wall distances. As the user's booklet explains, 'Moving the speakers further from the walls will reduce the general level of bass. Space behind the speakers also helps to create an impression of depth. Conversely, moving the speakers closer to the walls will increase the level of bass. If you want to reduce the bass level without moving the speakers further from the wall, fit the foam bungs in the port tubes".

More conventionally, sets of adjustable floor spikes are supplied and are definitely recommended for most carpeted floors.

Performance

The plain but impeccably finished appearance of these loudspeakers conceals a number of technical embellishments, as I have said. The sound quality rises well above the plain or characterless, being quite explicit and ear-catching. Frequency coverage is unusually wide, with a claimed ±3dB response from 48Hz to 20kHz onaxis and -6dB points at 37Hz and 30kHz. My room plots confirmed this exceptional bandwidth and indeed, if one concentrates attention on the frequency extremes, the top end does extend 'for ever' and bass is far from reticent.

The presence region, about 3-10kHz, appears slightly raised so that centre images are given a forward feel. This improves intelligibility on voices without being overdone and provides excellent attack on brass and percussion. The very gentlest of high frequency roll-offs avoids any kind of harshness of tone, while individual instrumental timbres are faithfully reproduced. The grille cloth makes only a tiny difference to the sound but it was sufficient for me to prefer the greater immediacy with the grille removed in conditions where the drive units, particularly the tweeter dome, were safe from prying fingers or other domestic accidents.

Bass extends far enough to balance this energetic high end and gives a firm foundation to music of all kinds. The booklet's guidance on selecting the optimum wall distance, with or without the reflex vent bungs, is worth heeding. Loudspeakers that have this kind of low frequency extension are inevitably more room sensitive, and I did not like the spurious emphasis that too close a spacing caused. The plugs were quite effective but I was definitely happier with my usual out-in-the-room placements with the plugs removed so that I could savour the clean uncoloured bass effect.

High frequency dispersion in the horizontal plane is another good feature of the performance, though getting up out of one's chair does produce noticeable treble loss, showing that the vertical dispersion is relatively narrow. The wide frontal arc has the benefit of making the listening position for a natural stereo spread less critical and a sofa full of listeners should enjoy much the same tonal balance and left/right audio staging.

At 90dB the sensitivity is a shade above average so the amplifier power requirements are reasonably modest. I could easily achieve realistic sound levels in quite a large room long before any signs of strain or compression became audible. However, I would not recommend very hard driving of these loudspeakers - or any domestic designs for that matter - for fear of overload distortion and possible damage.

B&W manufactures bigger and more spectacular loudspeakers but this mainstream DM603 S2 floorstander can take on any of its rivals at its very reasonable price. It can be confidently recommended

Specification

Enclosure type fourth-order vented box

Drive units two 180mm (one bass, one bass/midrange); 26mm twee

Frequency range 37Hz to 30kHz (-6d0 points)

Frequency response 48Hz-20kHz ±3dB

Crossover frequencies 150Hz and 4kHz

Sensitivity 90dB spl for 283V at 1

Nominal impedance 8 ohms

Power handling suitable for use with amplifiers rated at between 25-150W

Dimensions 850H x 236W x 306D mm

Weight 19kg

Manufacturer B&W Loudspeakers (UK Sales) Limited, Marlborough Road, Churchill Trading Estate, Lancing, West Sussex BN15 8TR Telephone 01903 750750 Fax 01903 750694

UK retail price £549.95