Stereo Amplifier

Review: Harbeth P3 Speakers

Several BBC-designed loudspeakers have been manufactured under license over the past couple of decades by a select handful of British loudspeaker firms. A condition of the license has been that every loudspeaker made will match within narrow tolerances the performance of a BBC-held prototype, so that part of the quality control testing routine will normally be to check each unit against a local second-generation 'original'. A primary objective of these designs was to provide BBC studio and outside broadcast engineers and producers with reliable monitors in a range of physical sizes to suit the various monitoring locations. Therefore, apart from such self-evident virtues as robustness and reliability, the designers went to great lengths to achieve consistency in terms of sound balance from all their systems, large or small Above all, professional monitors should be tonally neutral, letting the listener judge the quality of the signals from his microphones without undesirable emphasis or coloration.

By far the most renowned British Broadcasting Corporation loudspeaker design has always been the baby of them all, the LS3/5A. This is almost laughably small in size-a real example of apparently getting a quart from a pint pot-but has proved hugely successful not only in professional applications worldwide whenever space limitations have ruled out it s larger brethren, but also amongst keen-eared amateurs.

This Harbeth P3 (retailing from £388.50 per pair depending on finish) can perhaps be described as a BBC design at one remove. It has practically the same external dimensions as the LS3/5A, which BBC engineers designed in the first place as a one-tenth scale model for some studio modeling research, and which Harbeth still manufacture (£350.50 per pair) but is in fact a new design. The new drive units have screened magnets expressly to permit placement of the loudspeakers in close proximity to a television or monitor screen. This relatively new requirement reflects the increasing need for professionals and home users to monitor TV sound in stereo for NICAM television and other video applications. Conventional loudspeakers can cause permanent colour distortion if brought too near the screen.

The drivers were computer modeled and comprise a 110mm bass/midrange with a soft PVC surround and a 19mm aluminium domed tweeter with a fine-mesh protective cover. The crossover network is moderately complex, a BBC tradition born of the need for optimum smoothness in the crossover region, particularly to provide accurate reproduction of the spoken word. There are 21 high quality components mounted on a fibreglass pcb, the coils anchored rigidly in large blobs of adhesive. Every component is individually measured and matched to ensure that each P3 performs like every other. The network produces 18dB/octave slopes on either side of the crossover frequency, around 3.5kHz, with the tweeter and bass sections completely isolated and wired to separate pairs of terminal/binding posts for bi-wiring if required. The terminals are not recessed and so the speaker cannot be placed hard back against a wall.

The closed-box cabinet is constructed of 12mm thick MDF boards, increased to 18mm for the front baffle. The inside surfaces are damped with bitumen and there is a good filling of plastics foam. The baffle is inset by about 3mm, probably too small a step to generate any serious diffraction problems, especially when the black foam grille is in position, held by its seven Velcro fasteners. However, though the tweeter mounting plate is flush, the 110mm drive unit is unusually set back about 10mm in its cut-out hole which I did think might produce some slight glitch in the dispersion characteristics. However, I have been told that it was a deliberate move to smooth out the off-axis response.

The drivers are set centrally in vertical alignment with the tweeter on top. All four sides and the baffle are faced with attractive matching veneers. The review pair came in very handsome rosewood, but teak or walnut are listed as standard, with rosewood, natural ash, black ash, mahogany and oak available at a small additional premium. Matching wooden stands are also available.

How they performed

Placement recommendations for these small monitors are fairly standard, though scaled down to a mere 1-2 metres cabinet spacing and 2-3 metres listening distance on account of the speaker dimensions and relatively low power handling, plus the expected space restrictions of the chosen room, OB (Outside Broadcast) van, etc. This corresponds to what professionals call 'near field' monitoring and does at least reduce somewhat the ratio of room, reflected energy to direct sound at the listener's ears.

It will make sense to avoid corner locations and set the loudspeakers as nearly as possible in free space. However, refined miniatures like this will almost certainly be used in smallish rooms where other acoustic restrictions exist and I would suggest that the rules should be broken whenever necessary to effect the most pleasing compromise. It will certainly be important to set the speakers at about ear height, say 70-100cm (27-40 inches) above floor level, to produce the optimum high-frequency balance and sharp stereo imaging. However, pushing the cabinets close to the rear wall, instead of the recommended 0.5m or more away, resulted in very few ill-effects, remembering that extreme bass is in any case rolled-off steeply below about 60Hz.

Tonally I found the P3s well balanced, with the inevitable bass shallowness nicely matched by the unforced treble. Music and speech remained detailed and articulate, with no distortion or edge on musical peaks or sibilants. Midrange smoothness was exceptional, with the on-axis response sailing along within 1 dB right through the crossover region. Listening anywhere on a wide horizontal arc produced a consistent naturalness of tone and good presence, making soloists or small ensembles appear as though almost in the room. This effect was very lifelike, for example, with the new recording by Angel and Celedonio Romero of the Granados 12 Danzas espanoles for two guitars (Telarc CD CD80216). Any lack of extreme bass was compensated by a welcome tightness in attack, due in part I suspect to the absence of panel or intern al resonances. This helped larger forces to carry conviction too, as for example in the world premiere recordings of Malcolm Amold's Seventh and Eighth Symphonies by Vernon Handley and the RPO (Conifer CD CDCF177, 3/91) where the dynamic range is about as wide as you will find on CD.

The below-average sensitivity rating, sacrificed in the bid for optimum smoothness of response, and limited power handling capacity definitely rule out the P3 for very loud pop music or very large rooms. Yet in its proper application as a faithful 'near field' monitor for the critical listener, it would seem to me to take us further along the hi-fi road than the aging LS3/5A, and merits a strong recommendation.