Harbeth HL MK4 Bookshelf speakers
To quote from the brass plate fixed to the back of the Harbeth Mk4, "This loudspeaker was individually made and tested by British craftsmen": words calculated to stir our I chauvinist spirits. Yet there is plenty of evidence from overseas sales that Harbeth loudspeakers also appeal to foreign eyes and ears. In fact this HL Mk4 model was voted a "Best Buy" in the Japanese Stereo Sound magazine.
To deal with the eye-appeal question first, this latest Mk4 version of Dudley Harwood 's well-established HL design is no more than a basic rectangular box but it is rescued from I being a Plain Jane by the use of good quality matched veneers of real wood- walnut or teak at £475 per pair as standard, black ash at £485 and virtually any other real wood finish to special order. The grille too is a relief from the usual cloth or stocking material, being a sculptured pad of black open-pore Declon having two vertical channels and genuinely transparent acoustic properties. Standard binding posts accepting 4mm plugs are recessed close to the bottom of the rear panel and the crossover is configured to allow bi-wiring (taking separate cables from the amplifier to the woofer and tweeter) if desired, though the dealer's advice may be needed. The internal volume is about 50 litres and the multilayer birch plywood panels are damped with bitumous pads and lots of acoustic foam, with battens at the seams. The enclosure is a bass reflex design with a large cylindrical port emerging from the bottom right-hand corner of the front baffle.
The principal change in the Mk4 relates to the bass driver cone. This was always a special feature of all Harbeth loudspeakers, the company being one of a number founded by or reinforced by the recruitment of former BBC Research Department engineers. Until about 1977, when Dudley Harwood founded Harbeth Acoustics, the BBC conducted extensive research into monitoring loudspeakers always with a view to producing neutral, life-like reproduction of voices and live musical sources. This led to the patenting of a plastics (polypropylene) cone material which the original Harbeth HL pioneered and the Mk2 and 3 developed further. The Mk4 introduces a new TPX material, said to be the lightest known thermoplastic, difficult to mould into a cone shape but possessing improved self-damping characteristics. The advantages claimed include higher efficiency, sharper transient performance and low midrange coloration. This 200mm bass unit has a cast magnesium chassis and hands over to the 25mm soft dome tweeter at around 2.5kHz via a 12-component high-quality crossover unit mounted on a fibre-glass printed circuit board. An autotransformer is used for factory setting of woofer/tweeter matching to within 0.25dB by comparison with a standard reference loudspeaker.
With each matched pair of loudspeakers comes a calibration certificate and the data plus a frequency sweep are kept on file so that notification of the serial number(s) can lead to the provision of an exact match in the event of damage.
How they performed
Driving the loudspeakers with good quality signals produced sounds which were both lifelike and lively. This is certainly not a dull loudspeaker (as sometimes happens when the desire to achieve a flat uncolored response results in a loss of both efficiency and attack). The axial response is commendably flat and extends without drooping to the upper limits of audibility. Directivity is rather narrow at high frequencies, but the foam grille diminishes diffraction effects at the baffle edges so that musical balance is preserved over an acceptably wide arc. Nevertheless, optimum placement of the loudspeakers would be worth striving for in the given room environment. The makers suggest angling them in by about 10" and this did indeed produce sharper stereo in my set-up.
Similar care should be taken with height. This is quite a sizeable loudspeaker but it will not give of its best standing on the floor. Again a position which brings the tweeter axis approximately in line with the listener's ears is recommended. This probably means a floor-stand raising the speaker at least 30cm (12 inches) from the floor, or else tilting the speaker on a shorter stand. The system is a 'free space' design and should therefore be placed at least 1 metre away from the nearest wall when critical listening is planned. Sensitivity was found to be about average so that quite high listening levels could be enjoyed with any reasonably powered amplifier. Impedance did not stray far below the nominal 8 Ohms, making this a trouble-free load.
I have described the sound from this loudspeaker as lively, and music with plenty of highs is certainly reproduced with a bright naturalness and pleasing presence. But the bass end is also handled well, sounding firm and adequately, if not spectacularly, extended into the lowest octave. This betokens well-judged design of the reflex geometry for the given driver to avoid dips and bumps at the lower extremities. Complex music could be enjoyed with all details decipherable and spatial realism well maintained. Speech, always a difficult test for loudspeakers, was admirably natural avoiding the chesty emphasis or over-sibilance that lesser loudspeaker designs so often introduce.
I rate this new Mk4 version of the Harbeth HL loudspeaker very highly. I t places neutrality higher on its priority list than exhibitionism: but if detailed yet faithful sounds are to your taste you should give this sensibly priced loudspeaker a trial.
