SPECIFICATION

Frequency response: 45-20,000Hz 3dB

Drive units: two 165mm bass/midrange, one 25mm tweeter

Sensitivity: 89d8 at I for 283V

Power handling: suitable for amplifiers rated at 15-180 Watts

Nominal impedance: 8 Ohms

Dimensions (H x W x D): 800 x 228 x 320mm

Weight: 20kg

Manufacturer: Monitor Audio Ltd., Unit 34, Clifton Road, Cambridge CBI 4ZW

UK retail price: £59900 per pair

WRITING a profile of the British loudspeaker manufacturer

Monitor Audio in the December 1986 issue, I mentioned that a new top-of-the-range model was in the wings and that it was expected to come in at around £600 per pair. True to their estimate in both senses, Monitor Audio released the R952/ MD at £599 at last year's Chicago Electronics Show.

Heading the range by some margin, the R952/MD is clearly aimed at the discerning audiophile, for whereas some of the models in the range are deliberately tailored to provide the kind of response which will highlight the dynamic aspects of music—especially important for pop—to an extent at the expense of tonal accuracy, here the brief was to aim at an essentially flat frequency response first and foremost but to do so if possible without impairing the dynamic performance. In common with a number of other companies, Monitor have reached the conclusion that the simpler a loudspeaker crossover circuit can be the less these elusive qualities are compromised, a goal which has become easier to achieve, whilst maintaining a reasonably flat frequency response, as drive unit technology has pushed forward and more inherently linear devices have been developed. Here the crossover really is a bare-bones circuit, comprising just a ferrite-cored inductor in series with the two bass/mid drivers and a capacitor in series with the tweeter. These are of course firstorder filters and provide gentle 6dB/ octave roll-offs.

Although it uses three drive units, the R952/MD is in fact a two-way design. Two 165mm bass drivers are connected in parallel to provide an overall cone area equivalent to that of a much larger single driver while at the same time neatly circumventing the problems of linearity and break-up almost inevitably asso ciated with large cones. Here the two drivers are mounted above and below a single 25mm metal dome (hence the suffix MD) tweeter. This tweeter is a very neat piece of work, its aluminium dome and coil former being fabricated as a single piece for maximum mechanical integrity and essentially piston-like behaviour. Ferroflui-d damping and a series of vent holes around the top of the voice coil combine to provide excellent control and excellent power handling ability, and the whole moving structure is terminated by a rubberized PVC surround. This tweeter has already received much favourable comment and has been paid the back-handed industry compliment of appearing un-acknowledged elsewhere. The bass driver has a cast chassis with a large magnet and uses a polypropylene-derived cone with an inverted (concave) dustcap. This, again, is very simply located and is terminated by a nitrile rubber surround. Both these drivers are made to Monitor's design and specification by the specialist British drive unit manufacturer Elac.

As befits the top model, the cabinet is the largest in the Monitor Audio range, although it is modest indeed when compared with some of its competitors: 800mm tall with a footprint of just 320 x 228mm. It is a floor-standing model and comes with three threaded bushes in its base into which adjustable spiked feet can be inserted to provide a good, stable mounting, which is particularly important with such a narrow cabinet on carpeted floors. The cabinet is a closed-box, so-called infinite baffle type and is made from balanced veneered (i.e. veneered on both sides to inhibit warping) medite (MDF). As usual with Monitor Audio this is manufactured at their own cabinet workshops, MQ Cabinets, and is superbly done, with matching veneers which cover five of the six cabinet sides, the rear panel being finished in a matt black paint. At the mid point of each side can be seen the end-cap of an internal tie-rod which couples the panels together. This is employed to inhibit the major resonances which would otherwise obviously colour the sound. Internally the cabinet is lined with 50mm acoustically absorbent foam.

The three drive units are flush mounted towards the top of the front panel and are covered by a removable fabric-covered MDF grille, leaving the lower eight inches or so of the veneer visible. Visually the effect is very unobtrusive and the proportions of the whole units are most attractively balanced. The rear panel has an inset block which carries a single pair of terminals of the sort which will take 4mm plugs or bare wire ends. There is no provision for bi-wiring, as is currently popular elsewhere, but then with such a simple crossover there would probably be little point.

How they performed

With an impedance which is well maintained at around the nominal 8 Ohms figure (minimum of around 7 Ohms) and a sensitivity of 89dB/ Watt/metre the R952/MD will suit the great majority of amplifiers; certainly it makes no special demands in this respect and a very broad range of between 15 and 180 Watts per channel is quoted. A booklet covering the entire "R" range is included in the packaging and this gives helpful advice on setting up, although as always some experiment over the precise location of the speakers in the room will be neccessai-y.

Initial experimentation with pink noise quickly established the best siting for the loudspeakers in my room, their basic tonal qualities and their general dispersion characteristics. As regards the latter the re sponse is smooth and wide in the horizontal plane, as might be anticipated of vertically in-line drivers in a narrow baffle, but rather, less forgiving vertically. The 'brightest' response obtains, not surprisingly, with the ear at about the same level as the tweeter; much below or, more realistically, above and the top rolls off considerably. In practice, with the speakers some distance from the listener, this won't be a problem but in small rooms with a small listening 'triangle' it could be worth either tilting the speakers back slightly or raising them on some kind of plinth. I also discovered that the results were preferable—to my ears at least—with the fabric covers removed, and this is probably due to the 18mm thick grille frames which have squareedged cut-outs surrounding the drivers, and these will affect the diffraction.

In most respects these speakers are a delight; certainly in terms of their ability to create a fully-dimensioned sound-stage they have few equals regardless of price. The clarity of detail is enormously impressive and with careful siting it is possible to generate an image which occupies the whole area between, around and beyond them, making it hard to believe that they are the only sound source. The sealed enclosure gives a very tightly controlled bass perform ance at the expense of very much ultimate extension—the quoted - 3dB point is 45Hz—but what there is is both well behaved and responsive. I would certainly go for the cleanliness of this kind of response in preference to deeper bass which was in any respect tonally compromised. The presence region appears to be slightly lifted which of course enhances the clarity but it is not undue and can be ameliorated with careful positioning of the units. The real star of this loudspeaker, though, is the tweeter, which is crystal clear and well nigh as transparent as a good electrostatic.

Despite its simple crossover I could detect no obvious anomally as bass/midrange drivers gave way to the tweeter. Indeed the only negative aspect of the performance so far as I am concerned is a small degree of coloration, a slight hollowness imparted to the voice in the alto range (for countertenor enthusiasts René Jacobs's "Erbarme dich" in the Herreweghe versions of Bach's Si Matthew Passion (Harmonia Mundi (D HMC90.1155/57, 11/85) takes on a shade more of what one might call 'resonance'). That apart I can find little to fault. For a very reasonable price you get a superbly finished, elegant cabinet and a remarkably even-handed and musical performance.IVOR HUMPHREYS.