MAGAZINE: HIFI NEWS, UK
EDITOR: STEVE HARRIS
Now updated and available in any colour you like, this German horn hybrid sounds really cool too.
By Steve HarrisHIFI NEWS & RECORDS REVIEW, England, Issue May 2000
Though far from being Germany's only maker of horn speakers, Avantgarde Acoustic seems to have become the breed's best ambassador In this country, when people talk about horn loudspeakers, they usually mean a horn-loading enclosure designed around Lowther full-range paper cone drive units. In these designs, the mid and treble comes from the front of the driver, while the bass comes from the back. Usually (though with a few notable exceptions, such as theCafraehorn) the cabinet forms a 'folded horn', in which the all-important pathway from the rear of the driver is doubled back on itself to fit into the cabinet. The concept dates back to the dawn of hi-fi, when amplifiers only produced a couple of watts and so the loudspeakers had to be made as sensitive as possible - which is what horn-loading, uniquely, can achieve - and when, in fact, full-range drive units were the norm. But in other places, the development of horn loudspeakers has taken a few more steps. Here, we expect a horn loudspeaker to look like a wardrobe: In Germany, a horn speaker looks like a horn. And all the sound comes from the front.
Though far from being Germany's only maker of horn speakers, Avantgarde Acoustic seems to have become the breeds best ambassador abroad. The UNO is Avantgarde's smallest model, it still stands 1450 mm (57in) high. It has horn-loaded units for the midrange and treble, plus an active (self-powered) subwoofer cabinet for the bass. This approach is dictated by the fact that the lowest frequency you can get from a horn is proportional to the size of the horn mouth. Even the biggest horn of Avantgarde's top-of-the range, three-horned TRIO, nearly a metre across, doesn't extend below 100Hz, and is usually supplemented by a sobwoofer. The UNO's midrange horn is 570mm in diameter and operates down to around 220 Hz.
Avantgarde's horns are moulded in ABS plastic, a material which, although tough, is relatively 'floppy', so that the resonances are well below the operating frequencies. There are 'spherical' horns, and open out to an included angle of 180 degree at the mouth. Avantgarde claims that its correctly-calculated horn flare gets rid of the colorations found in other horns, and gives a wide and well-controlled dispersion. The drive unit at the back of that big midrange horn has a 2in diameter dome; naturally, the tweeter, with its 180mm diameter horn, has a smaller diaphragm (dimensions not specified); but its massive 3.5kg magnet maintains a claimed sensitivity of 100dB/W. Although there is some restriction at the throat to control the upper cut-off point, there is no real compression chamber. The electrical crossover has been kept as simple as possible, the horn-loaded units being made to provide 18dB/net acoustic rolloffs.
In any hybrid speaker, the difficulty is to combine two different kinds of drive to produce a scainless whole. Hi-fi history is littered with designs in which 'fast' exotic electrostatic or ribbon treble units were unhappily married to a 'slow', conventional bass. And with the early UNO, the stunning realism of the mid and treble was not really matched in quality by the bass. Avantgarde addresses this first with structural improvements: The bass section was decoupled from the frame, and the frame itself was strengthened. (It also now allows you to dismount the drivers and set them at different heights.) However, the biggest change has been the introduction of a new subwoofer. The SUB225CTRL PRO is now available as an option with new UNOs, Duos and Trios, or as an upgrade for speakers fitted with the existing SUB217PRO type. the reflex ported cabinet and dual 7in woofers of the SUB217 are replaced by a pair of massive 10in long-throw drivers, designated 10T300 and developed exclusively for Avantgarde. Their paper-pulp cones are made by a sieving process rather than by moulding, giving an irregular surface on the rear of the cone and great stiffness. Voice coil diameter is 3in and the 7,6in (192mm) magnets weigh 15lbs (6,5kg) each. These drivers are powered by a built-in 200W amplifier, which also gives active control of the speaker through a 'Velocity Controlled Driver Feedback' system. this reads current and voltage to deduce the speed of the driver compared with the input signal, and corrects any deviation by an increase or decrease of power. Frequency response is said to be flat from 18Hz to 250Hz within +/-0.8dB. A soft-start circuit brings power in gradually, avoiding any possibility of swithon rhumps through the speakers.
All this power and speed wouldn't be much good without a suitably solid foundation for the drivers to work against. This is provided by a cabinet 550x300x550 (hwd), made of 30mm MDF. This, along with the massive drivers and electronics, means that the subwoofer alone weighs a rather groin-straining 45kg (100lbs). The back panel is recessed, which looks neater and means that the units can be placed on their backs without damaging heatsing, control knobs or terminals.
The UNOs were run in using my trusty old Musical Fidelity A1000 integrated amplifier, an unlikely but effective combination. Avantgarde's UK importer, Graham Tricker of GT Audio, once more loaned me a set of his own Tron amplifiers - the beautifully-made Tron Nucleus tube pre amplifier and phono amplifier plus single ended triode stereo power amplifier, which I reviewed last year (Aug '99). I was also lucky enough to have access to have the use of a pair of Capary CA300 single-ended 300B triode monoblock power amplifiers, to drive these I mainly used the Viking 1 tube line pre-amplifier by Vidmar of Slovenia. When the UNOs arrived, Graham warned me that they were absolutely new and would need running-in, and he was right. In fact, for the first few days I even found myself comparing them unfavourably with the old pair, which of course I'd lived with for many months. They just didn't seem to have the immediacy, the freedom or the magic which I'd learned to love with the original UNOs. Then, after about a week and a half, one day everything gelled. The driver units had freed up, and the new speakers lived up to the promise: They really were 'improved'.
The new UNOs now demonstrated those astonishing midrange qualities that had attracted me (and other commentators of course) to the Avantgarde speakers in the first place. They gave you immediacy, impact, emotional communication, but without the coloration which has spoiled these aspects in other horn speakers. They worked on all kinds of music and they sounded effordless. On solo instruments they could be stunningly real; on orchestral music, they allowed you to unravel musical strands without conscious effort, and instruments were placed in a stage that had depth and tangibility. Although it's an overworked word, 'transparency' really is what these designs can offer. On CD, they seem to unleash more realistic dynamics than other speakers, they can still sound sweet. On vinyl, they seem to allow you to listen further into the space which (as you suddenly realise) was captured on the original recording. Listening to a (pre-digital processing!) LP transfer from 78s, the Avantgardes allowed the car to differentiate so easily between noise and music that while low-level 'surface' remained, clearly-defined but not-too-distracting in the foreground, the musical event was palpably taking place in a space behind the speakers. It may seem ridiculous to judge a £5000 - plus loudspeaker on how well it reproduces the noise from a 78, captured on tape and transferred to vinyl at least 25 years ago, but the example illustrates the way the UNOs just don't get in the way. And I think this is what's most important.
One of the Avantgarde advantages is that the speakers are gloriously unfussy about room positioning. However, my experience was that if placed very close to side walls they will respond by sounding coloured - lending a honk to female vocals. Two feet away from the wall, everything was fine again. But I did conclude that the new UNOs were slightly sharper, slightly brighter in the upper mid. I couldn't guess if this might be due to internal changes, or to that hard coating of auto paint. Or a need for even more running-in. So what about the bass? With those early UNOs, I'd tended to back the bass off more and more, preferring to listen to a bass-light sound rather than to be made sware of the contrast between magic mid and rather ordinay low frequencies. With the new sub, things were different. I spent more time fiddling with bass level/frequency controls - but with far more rewarding results. Ideally, you should employ a tame assistant to make the adjustments while you listen from the normal position. Even then, you may end up fine-tuning for different types of music. I feel that Avantgarde has overstated the case a little by suggesting that the bass is now a perfect match for the speed of the horns, but it is very good. With its very high published sensitivity, the Avantgarde is eminently suitable for small valve amplifiers; 10 watt single-ended-triode amplifiers will easily go loud enough. Paradoxically, the better subwoofer actually makes the UNO more demanding of amp quality. The sub has its own amplification and so makes no real power demands. However, the subwoofer's amplifier cannot make something out of nothing: if the bass quality of the chosen external amplifier is poor, you will certainly hear it. With some valve amplifiers, in other words, the subwoofer's qualities will be wasted.
Another point is that high sensitivity speakers make an amplifier sound more noisy. With the 100dB/W UNOs, background hiss or hum from the amplifier will be raised by 10dB compared with a pair of 90dB/W speakers, which could make the difference between acceptable and unacceptable results.
With all this in mind, I picked on the news that some Avantgarde dealer were selling the speakers with a budget CD player and amplifier, which would produce good enough results and leave the owner scope to upgrade later. I didn't have a Mitsui CD player to hand, but (using an Exposure CD player) I was able to try a budget Cambridge amplifier. The results were frighteningly good, especially on rock. The cheap solid-state amp lacked the refinement and/or warmth of the valve amplifiers I'd tried, but basically, it worked. The midrange still had that precious immediacy, without shouting, and the bottom end now had punch and pace.
Avantgarde's speakers are not cheap, but I think that the results justify the cost. You also get some serious engineering, including high quality electronics and excellent drive units, combined with a now well-proven approach to horn-loading, and real visual pizazz too. I think that for sheer enjoyment, they more than stand up to conventional 'box speaker' competition at the price. Or you spend the same money (or considerably more) on a pair of Lowther units in complex bespoke cabinets, but I'm afraid that for me there is no longer any contest. The Germans have it every time. Avantgarde's UNO is available with the horns in polished, unpainted white finish at £ 5.600. The standard metallic paint options, Midnight Blue or Brilliant Red, are an extra £1.500, while any customer-specified auto finish (like the Porsche Boxter Jade colour seen here) will add £1.700 to the basic price. Pure silver internal wiring (as in the review pair) is also an optional extra, at £250