DUO REVIEW

AVANTGARDE ACOUSTIC DUO with SUB217 PRO subwoofer

Test review by Chris Beeching (Audio Quarterly, UK, Issue Q3 1999).

These big bangers from Germany present one grandiose version of speakers of scale and importance. Did they sizzle or whimper?

Avantgarde is a smallish company based in Germany. They make a small but perfectly formed range of horn-based loudspeaker systems, which are nothing if not distinctive.

Born of a love of both music and low-powered amplifiers, Matthias and Holger settled on the horn as being the most efficient coupling from amplifier to 'air' and set about researching the best way to use the horn's inherent strengths and minimizing its weaknesses.

The result is a range of three loudspeakers, the Unos which are the most compact, the Duos (reviewed here) and the Trios.

The basic diffence between the models is as follows. The Unos are a compact version of the Duos - both feature treble and midrange horns, and active bass units. The Trios comprise three horns including a true bass horn, but also with the option of an add-on active sub to really plumb the depths.

The system sensitivity for the Duos is over 100dB/watt, which means that 3 watts is plenty to drive them to deafening levels. The Trios boast nearer 106dB.

Siting these not-so-small speakers in my usual listening room proved an interesting prospect, but as the house is Art Deco in period and we've tried to furnish it in that style, aesthetically they fitted in quite well. As mentioned above, the Duos feature an active bass unit, and this supports separate controls for the bass turnover frequency as well as the degree of bass volume for a given input. There is no connection to the system other than the conventional (4 mm) sockets and a mains (in my case IEC) socket. Effectively the horns are fed directly from the main (i.e. existing) amplifier in your system, and the bass units are powered by their own internal amplifier and crossover.

Coupling the speakers to an amp and powering them up was an unforgettable experience.

Suddenly the room was filled with effortless music. Absolutely effortless. These horns are so immediate and so revealing, that it's readily abundantly clear what's playing, where it is, and the range of dynamic contrasts is phenomenal.

My initial amplifier connected was a humble Quad II. Not necessarily the ideal partner, but even with the amount of feedback in that circuit, the presence and dynamics were amazing. What came as more of a surprise was just how quiet the power amp was. There was no residual hum, and the noise floor was so low that you really had to put your ear to the mid- or treble horn to hear it. The bottom end was tight and deep, and there was no hint that this was an older amplifier design. Substituting the IIs with Don Garber's renowned fi amps with their single 2A3 output tubes, and a whole new vista opened up.

Now the differences between push-pull and single-ended designs were abundantly obvious. I have to say that although the differences are quite wide in some respects, they do each have their own (very different) merits, and should not be criticized simply for being different. That the Duos are so easily able to show these differences (and in my experience even more sharply than in any other speaker system) speaks more about the Duos' abilities than the merits of one amplifier topology versus another.

Up until now, I have had reservations about horns.

Despite the apparent gains in terms of efficiency and immediacy, their room-size requirement and need for a very quiet amplifier have made me a little wary. On systems I have heard in other environments, and at larger listening distances than are achievable in my listening room, I have found horns to be very very good in pretty much every aspect. As far as sound quality is concerned, it is, like panel speakers, so different from the 'boxed cone' sound we find almost everywhere that it can often sound very odd to begin with, and the apparent need for a large room will no doubt put many off. Their physical size has always been a determining factor too, and even the smaller ones aren't that small. The Avantgarde package goes a long way to minimizing the downsides of those needs, and the Duos package is very well thought-out.

Standing some 2 metres tall, the Duos have a very small footprint, barely more than a good-sized floorstander of conventional design. Roughly 15 inches wide and 24 inches deep (sorry for the mixed measurements!), the larger dimensions of the mid-range horn don't become a 'problem' until you're about 5 feet up where the horn flare opens to about 30 inches at head-height. The front-to-back measurement is also about 30 inches here, so long as you don't try to back them tight up against the wall and hard against a sidewall, you should be fine.

On our review, set the main horn mouths were in white ABS plastic and the active box in satin black.

Getting the sound quality right took some fiddling, but after a while you realize that even though there are user-adjustable elements to the bottom end, in fact because the speaker is so revealing, you can hear when the recordings are bass-heavy or light, and how clear, or shrill, or softened the upper reaches are.

Having been more confused by recordings than I expected, I settled on an even balance with a sweep-tone generator (NOT my usual practice) and just tweaked the turnover frequency one notch after some longer listening.

As far as sound quality was concerned, everything was so immediate that I had to relearn how to use the volume control on the preamp.

The opening of the "Montagues" and the "Capulets" from Prokofiev's Romeo and Juliet nearly blew the back wall away, and I then found myself sitting right in the middle of the tracks when Oscar Peterson's Night Train came whistling through.

But after a couple of experiments where I limited myself to single instrument recordings to get a feel for the overall level of things, something akin to reality (normality) returned.

It has to be said that these are not forgiving speakers. They are certainly not ruthless, but they won't make any iffy recordings sound 'nice' or 'okay'. They make them sound just how they are - iffy or okay. The plus side is that when you chance upon a really good recording, you really get the benefit, and vocals in particular are brilliantly well portrayed.

I had often wondered about the wisdom or otherwise of marrying a sub-woofer system to any non-traditional driver speaker system on the basis that the woofer is unarguably slower than either an electrostatic diaphragm or a horn driver. Having recently heard an electrostatic-woofer marriage which was as near perfect as I could ever have anticipated, I was now faced with a similar overthrow of my suspicions with a horn-woofer combination.

I lost.

Although as with any dissimilar speaker types, careful siting is of paramount importance to avoid the various cancellation and difference in radiation pattern anomalies, the Avantgarde Duos were also as near perfect as I could ever expect. The active crossover and bass amplifier drove those small bass drivers incredibly well, and even with the sweep-tone test, it was very very difficult to hear the joints.

The other thing to bear in mind is that the usual perception is that bass is slower than the upper frequency regions, and here with a good active crossover and power amp built-in, this apparent slowness is more than compensated for, with the result that the bass sounds as quick and deft as the horns themselves. I'm sure an impulse test would prove me wrong, but aurally they sounded fine.

The advantage that the Duos have is not only in their adjustment of bass volume with respect to the rest of the system, but that turnover frequency is also variable between 80 and 150 Hz which makes system-tuning very easy given time, care and patience.

In practice, this makes it very easy to tune the system to give an extended low frequency response without that bottom end becoming overwhelming. Much of the ambient information that we use as clues to determine the size of the recorded venue is in the almost sub-sonic region, that 10-going-down-to-two-Hz region. This is, in fact, the resonant frequency of the mass of air within the venue. The smaller the mass, the higher the frequency until, as with some studios, it falls between the normal 20-20k region that most hi-fi systems aspire to. With vinyl replay, this low frequency is very discrete, and is often masked by turntable 'noise' or record surface noise. However, with CD there should be no excuse, and some of the best 'ambience' can be caught off CD with its almost limitless bottom-end performance.

Electrostatics and horns have great difficulty in producing these low frequencies in a domestically acceptable package-size.

However, using cone-drivers (as do the Avantgarde Duos here) and a carefully designed amplifier and active crossover, very low frequencies are possible. Again, the music-lovers who prefer valve amplifiers may find that their beloved tube amp won't go that low, (and it's especially true for the single-ended brigade, due to increasing output transformer saturation at below 10 Hz) so ironically it may be that solid-state amps will fare better in this department, which is NOT what 'they' say you should drive horns with!

The Duos are quite happy with solid-state though, whether it's a Levinson or Krell, or even a humble Pioneer or Arcam. It must be good, though, otherwise it will sound really horrible. The Duos aren't sensitive to power output (or is it input?), but they are sensitive to quality, and poor?in? will definitely result in poor ?out?!

I had not expected to enjoy the Duos as much as I did, but some words of warning are in order here. I have always been a fan of the original Quad ELS57, and you will find much (many?) of my musings on this venerable design on some other pages within this issue. I believe the '57 are one of the finest speakers ever designed and built. It is flawed, and I would not try to protest otherwise, but for many, including me, it has strengths that some cannot live without. These include mid-range transparency and an overall uniformity of speed and presentation. However, they are limited in their ability to generate bass at large volume levels, and their dynamic range is also limited.

As a consequence, I had expected the Duos to sound coloured, ultra-dynamic, and to a certain extent the sum of two rather obvious parts. That is not the case. They are very dynamic and given a good pre-power amplifier, they can exhibit stunning ranges of subtlety, dynamics and ultimate loudness. They can give exemplary imaging to recordings and they have a pretty much seamless top-to-bottom even frequency response in-room. They are also very uncoloured. The have just enough about them to make the music really come alive yet just err on the side of neutral. Not totally neutral, but pretty much neutral. This has been achieved by very carefully using materials which complement the horn's needs, so the grade and thickness of the ABS plastic used for the treble, and the mid-range horns is different, each according to needs. Because Avantgarde uses horns, these are speakers that are very much alive, and they certainly make listening to music great fun, regardless of music type.

But if we sit back and regard these in the cold light of day, rather than just sitting here waxing lyrical, how good are they?

They are one of the best speaker systems I have ever heard. Their presentation of music is up with the best I have ever heard. They have transparency and immediacy that many speaker systems are still striving for. The have an uncanny presence and immediacy, and to me their dynamic range matched more closely to real life than anything else I have heard. With an 'integrated' active bass they convey the weight of the low frequency with (so it seems, anyway) the speed of the horn drivers, which is more of a tribute to the bass engineers than the horns, and for a speaker of such diverse parts, its performance is absolutely astounding.

To people who questioned me about them I found myself answering, "It's quite uncanny. I would have sworn Joan Armatrading was singing in my living room, but then so was Harry Christophers and his Sixteen, and Louis Armstrong, and Pat Metheny and..." ...and... and... and the neighbours kept finding excuses to visit.

They will not suit everybody, nor will they work in small rooms. Although they make music very immediate, they also need to be some way away from you, but that is a caveat that applies to many speaker systems. They also produce a large amount of (not necessarily loud) sound, and initially this can be a little overwhelming, but later when you go back to conventional speakers they, in turn, sound horribly small.

So, to conclude, these speakers are simply the best I have ever heard in my domestic system.

Nothing else has come to close to recreating the power and finesse of a full organ, or bringing a full orchestra into the living room, and conveying the emotion of a solo performance.

Their efficiency makes them so easy to drive that going back to 'conventional' speakers certainly left me short-changed in the dynamic contrasts and subtleties of musical performances. They also work equally well with tubed and solid-state amplification.

Electrostatics now have a serious contender in the transparency stakes. These horn systems are so revealing of the sources and recording environments that it's hard to imaging using anything else. My favourite reference speaker is now ousted in favour of these music-making devices. Don't be swayed by people telling you they don't perform and are coloured. These speakers make music in a way that you simply can't argue with.

Chris Beeching, Audio Quarterly, UK, Issue Q3, 1999