Jamo 507 loudspeaker

Isuspect that a few incredulous eyebrows will be raised when I say that Jamo is Europe's largest loudspeaker manufacturer, for their presence in the UK has been decidedly low key until recently. I first came across some of their products towards the end of the 1970s when our Goodmans Industries, then a hybrid of Thorn and Plessey, imported their Power Range which was aimed at Discos and Rock fans. At that time the Danish Jamo company were only a few years old and had established themselves at Glyngøre in the north of the country. Now they have a 20,000 square metre factory (over 200,000 square feet— remember that land is much cheaper in under-populated parts of their country) and there their 250 employees produce around 600,000 loudspeakers a year to a total value of 300 million Danish kroner (about £31 M). The majority (over 80 per cent) of this vast output is sold in Europe and Scandinavia and there is still the Middle and Far East to conquer and north America to develop.

In the summer of 1990 Jamo UK Limited was established with an office and warehouse at Daventry in the heart of England, and their attractive and often unusual designs began to make their appearance at our audio shows where they have attracted comment in our columns. In less than four years in the UK they have appointed 500 retail outlets which now account for seven per cent of their production. A clever piece of marketing was the acquisition of a double-deck bus, which they sumptuously equipped as a mobile showroom and indeed this Jamo bus has become a familiar sight at many events. Live '93, held last September in spacious Olympia, enabled them to drive the bus on to the company display stand and it was there that I spotted the beautifully styled newcomer, one of over 90 different models, which is the subject of this report, our first on a Jamo product.

The Jamo model 507 is top-butone of a group of five in their "07" series, the 707, the other floor standing model, being a scaled-up version sharing its appearance and unit complement. I suppose what first attracted me to this design was its elegantly curved sides. Modern, largely automated cabinet manufacture abhors curves, particularly those with real wood veneers; it much prefers working in only two dimensions with flat sheets. You might have noticed that, even when designers have insisted on rounded corners to mitigate acoustic diffraction problems, they are usually formed by inserted shaped solid wood fillets. In this 507 the two sides are of a sandwich construction, where an inner core of grooved chipboard has a curved MDF panel glued to each side. In the review samples a very good quality dark red satin mahogany/ rosewood vinyl veneer provides the finish, but a black version is also available. There is a thick solid MDF plinth and a polished black glass top plate. The narrow front baffle and rear wall are finished in black, the former of cloth over a thin MDF frame; the top third, above a neat black logo, is removable to expose three drive units. The two outer units cover the midrange and bracket a softdome coated-membrane tweeter. Internally, these three are isolated by partitioning and damped with profiled acoustic foam. A further horizontal partition provides a baffle for a pair of long-throw bass drivers mounted face-to-face and driven in parallel. The upper one works into a sealed chamber; the lower is provided with a reflex port set in the rear cabinet wall. Once again damping is provided by a lining of acoustic loam. Below this, near floor level is a recessed four gold-plated terminal panel with links and 4mm socket holes. The crossover network is built on a board which directly connects to the rear of these terminals.

The twin bass units are of fairly normal construction built on pressed steel chassis of 165mm (6'/2in) outside diameter. The thickish paper cones are 125mm across and are suspended on convex rolled-foam surrounds. The long-throw coil appears to be 25 or 26mm in diameter and has a DC resistance of 56 ohms. There is a standard ceramic magnet assembly plus an additional ferrite ring acting to oppose any stray field which might affect an adjacent TV set. The free-air resonance of these units was 60Hz. The two midrange drivers are also on pressed steel chassis, this time 115mm overall diameter, with unusual 80mm double cones. The inner, steeper small cone is directly driven by the approximately 25mm voice-coil of 58 ohms DC resistance. The main diaphragm, consisting of three parts, large dust cap, membrane and convex rubber roll surround, is "pressure diecast into one unit". The inner drive cone is attached at the circumference of the dust cap. The ceramic magnet assembly is quite large for this 4in unit but no cancelling ring is deemed necessary. Freeair resonance was at 80Hz, nearly an octave below the unit's operational range which extends from 150Hz to 3kHz, above which the 25mm dome tweeter takes over. This unit has a coated textile diaphragm and an aluminium voice-coil former working in a ferrofluid gap (although everyone calls it ferrofluid I'm told the preferred term is magnetic oil).

Performance

As I have described, the bass loading arrangements are somewhat unusual, being yet another variant on the so-called coupled-cavity configuration which is rapidly becoming the favoured way of extending bass these days. In this case the impedance curve shows two in-box resonance peaks at 56 and 86Hz with a rather nasty dive to a minimum of 25 ohms at 125Hz. Allowing for the fact that this 507, in common with many European and most Scandinavian designs is quoted as a 4 ohms device it implies that the user possesses amplification capable of supporting the higher cut-rents that will be called for. Sensitivity is stated as 88dB for 283 volts applied, which was within my check to a reasonable margin of error, but the low impedance meant that the supplied power at that was nudging 3 watts. A true LW sensitivity was more like 84dB.

Measurements in the favoured room location made with thirdoctave pink noise into the pair produced a reasonably flat coverage of the important frequency range and showed that there was still output as low as 30Hz. However, the sound of the pink noise was recognizably changed in some segments in the area around 200Hz, which tied in nicely with a tendency to a previously noted belllike character imparted to piano tone and a certain throatiness Specification Type Three-way with reflex bass loading Drive units 165mm bass, 2 x 102mm midrange, 25mm tweeter Frequency range 40Hz-20kHz Sensitivity 88dB/W/m Nominal impedance 4 ohms Crossover frequencies 150Hz and 3kHz Power handing 150W long-term, 200W short-term Dimensions (H x W x D) 915 x 223 x 365mm Weight 19kg Manufacturer Jamo A/S, Elmevej 8, P0 Box 220, DK-7870 Gtyngore, Denmark UK distributor Jamo UK Limited, Jamo House, 5 Faraday Close, Drayton Fields, Daventry, Northants NN1 1 SAD. Telephone 0327 301300 UK retail price £69999 per pair added to lower soprano and certainly contralto voices. Nowhere near enough to be damning you understand, but something to be aware of although several listeners did not notice it until it was pointed out to them.

I have listened to a very mixed bag of programme material on these Jamo 507s during the last couple of weeks and can report that on many things they sound superb but on others minor imperfections lead one to think that our leading British manufacturers have the edge—except perhaps, in that elusive happy styling which eases them into domestic acceptability. I have only come across one other loudspeaker in recent years which has drawn unaskedfor approval from lady visitors and that was British, Oliver Brooke's Pentacolumn. Successes were the last of the Panufnik recordings sponsored by Technics (One hopes the management changes there will not affect future sponsorship for which they were earning increasing acclaim) his Concerlino for timpani, percussion and strings etc. (Conifer (D CDCF2I7, 8/94). Strauss, Til Eulenspiegel from Abbado and the Berlin Philharmonic before an audience in their own hall (Sony Classics D SK52565, 7/93). Also from Sony on D SK 48484 you can hear some astounding piano fireworks from Emanuel Ax (11/93) but the single notes in the left hand showed the tonal hangovers of the Jamos. Confidence was restored by a disc given to me by Peter Baxandall (he of the famous tone control circuit) John Scott Whiteley playing a concert on the Christian Muller organ of St Bavo's Church in Haarlem (Priory (D PRCD 265, 10/89). This 1738 original has undergone much restoration and rebuilding but still happily renders the works of Bach and Buxtehude in a manner they would have approved of; a natural wide frequency range recording which explored the Jamo's limits to the full. The latest offering by The Tallis Scholars, works by Josquin des Prés and Cipriano de Rore on Gimell D CDGIM 029, 6/94 sounded rather harder and more 'shouty' than it should, but the smoothness of sibilants showed the excellence of the Jamo tweeter.

Perhaps a shade less accurate in their reproduction than they might be, these Jamo 507s will nevertheless find ready acceptance with many listeners and certainly their rendering of popular music and accurate stereo positioning, resulting from the narrow front face, are bonus points. But perhaps their major advantage, when you come to choose, will prove to be the nudging elbow of the houseproud lady in your life