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DUO 2.2 REVIEW
Review: Avantgarde Acoustic DUO

HÖRERLEBNIS issue 40, 2002

by Alexander Aschenbrunner

DUO FANTASTICO


Hornspeakers have always fascinated me. Numerous HiFi magazines have covered them - and controversially. Some HiFi reviewers strike me as Pavlovas (Anna Pavlova, 1881 - 1931, one of the most famous ballerinas ever). Rather than following and describing their emotional reactions, these writers' statements about Avantgarde Acoustic products perform heady and ultimately elusive verbal pirouttes. Call me slow, but how do terms like "attack response" supported by fancy diagrams describe music? How does "homogeneity" relate to music reproduction? Last time I checked, the term derived from the Greek to connote "common origin", meaning "same" or "sameness" in everyday use.

Hence, one such review description becomes: "... a very beautiful reproduction of sameness..."

Clearly music isn't synonymous with a constant output of 1 watt. Who defined the term "High-End" anyhow? And who, and under what authority, can define "World Class"? High-End's always on a merry hunt for superlatives. To me it smacks of high-scale fetishism.

What gives? I needed to know and duly arranged for a pair of DUOs. Soon thereafter, the firm's Armin Krauß and Matthias Ruff showed up. Armin Krauß handles customer service while Matthias Ruff, jointly with Holger Fromme, must be "blamed" for Avantgarde's actual existence - within the company, he handles research and development of the various models.
Making appropriate room in my listening environment, the horns soon found their ideal placement with surprising efficiency. Before I knew it, they were set up. That's something my reading about the presumably "difficult setup" protocol with hornspeakers had indicated would take much longer.

We bridged the initial settling and breaking-in period with some discussions about Avantgarde Acoustic's corporate philosophy. "Experiencing live music as though you were present" was Matthias Ruff's condensed mission statement. It's based on his hornspeaker designs since the mid 80s (the first TRIO appeared 1986) and learning from self-professed mistakes. "One should be able to listen through opened doors". That's an important statement. "In pricinple, that's a very basic affair", added Ruff with a malicious grin.

Conceptually, hornspeakers are the most natural physical means of sound reproduction. Everyone knows horns. They're sound pressure transformers. In concert with a sound source, they operate in complementary opposition to the human ear. The ear's narrowing funnel continuously increases pressure from the outer pinnea receptor through the ear canal to the actual ear drum. This inverse horn shape creates our acute sensitivity to pressure changes, hence better hearing. In a hornspeaker, a diaphragm membrane is placed against the inner horn mouth. The art resides in fabricating the surrounding horn such that it colors the sound as little as possible - or, ideally, not at all.

Audible colorations? That's a common complaint horn critics level against the breed. "Well", comments Matthias Ruff, "if you do it properly, it's no longer an issue!" Which, in this instance, means absolutely uncompromising quality standards. Not surprisingly, that translates into maximum allowable deviations from the horn shape's tolerance of 1/500th of a millimeter. Hence, fit'n'finish call for an unhesitating reviewer's grade of A+.

The horns are molded from ABS plastic, a material inherently more compliant than GFK and accordingly not subject to co-resonant breakup modes in the critical midrange. Naturally, the actual angles of curvature don't follow the whim of the designer but are the result of precise mathematical formulae. The goal is simply to amplifiy the wave form between horn mouth and bell and radiate it into the room without coloration or distortion.

As regards sound propagation, the above-mentioned "Pavlovas" insist that Avantgarde's bass can't follow the remainder of the horn-loaded spectrum. Even accounting for the fact that such statements were made about older than today's review versions, I can't imagine such "lagging" low frequency performance.

High frequencies do propagate differently (faster) than lower ones. To wed spherical horns with "conventional" sub-bass cabinets for such fantastically coherent bandwidth unity is truly Avantgarde Acoustic's real accomplishment. I can no longer stomach the conceptual nonsense that, for some time now, has been inflicted upon unsuspecting music lovers and listeners. I'm certainly not perfect but do make it a point to remain well-informed while broadening my learning. On the other side are the apparent specialists who rather rest on past laurels to pamper their auras. Granted, that's human nature. But to maintain that this manufacturer causes shortcomings in the playback of music -- this is where misinterpreted analytical sharpness enters the picture -- is, to my mind, a fatally flawed argument.

I think of this, as so often, as a lack of inspection of personal bias and how the subject of hornspeakers is approached in general. As an aside, the term "analytical" stems from the Greek too and means "to divide" or "dismember", not "unpleasantly edgy representation".
Adds Armin Krauß that hornspeakers aren't unlike mimosas - they don't tolerate errors. That's what fascinates me about such systems. I've subconsciously felt for a while that hornspeakers could be "my thing". First live concert encounters date back to the 70s, with a Pink Floyd session a particularly fond memory. Even today, their music makes up some of my favorite musical sustenance.

I'd call the accoutrements of Avantgarde's speaker system discretely "lavish". Due to the flexibility of the adjustable dual active subwoofers, I can't imagine a room where they wouldn't perform. According to the specs, the DUOs are suitable for rooms of 20 square meters or larger.

I don't at all mind confessing how diligent study of the owner's manual was required to take full advantage of said adaptability. Prior familiarity with my room's intrinsic bass rise due to constructional elements assisted in quickly finding the optimal settings. The rear-fitted crossover controls next to the 250-watt amplifier heatsinks adjust the bass balance to the horns. Depending on taste, the subs' filter can limit from 60 to 220Hz, hence the crossover setting -- properly dialed -- can be used as a warmth control. Set deliberately higher than delivered, this creates added subwoofer overlap with the midrange horn to enhance warmth and substance. Too much overlap causes a loss of transparency and resolution.

In my space, I ended up at 140Hz, with the LF attenuator in its 10 o'clock position. Naturally, bass output is adjustable as well, in nice click-stop fashion. Too high a setting and the sound becomes fleshier, but the danger of course is an overall loss of coherence - the satellites and subs become identifiable as distinctly separate sources of sound.

During the dialing-in phase, I recommend deliberate overshoots to get comfortable with the results. Should the bass still seem slightly more powerful than natural, the subsonic toggle switch (selective at 20, 25 and 30Hz) can curtail it. My room was happy at 25Hz but went off like berserk vikings at 20Hz. Incidentally, the factory recommends 140Hz, 11 o'clock on the attenuator and 20Hz subsonic filtering as the starting point for fine-tuninging their speakers to individual environments.

To approach the idealized elongated listening triangle is a valid goal. I sit outside of 5 meters from the speakers while nursing a good malt when the occasion warrants. But such distance isn't etched in stone and subject to experimentation (as is the malt). Should the soundstage appear too chiseled, diminish toe-in by small increments until things lock in. Experimentation with different speaker cable to the horns is mandatory as well. I had Avantgarde's optional silver cable which had been made available together with my plain white review pair (further RAL colors available for an upcharge). The DUO responds uniquely to each cable. The efforts of mating it to the appropriate one is part of the overall system tuning. This holds equally true for the power cords to the subwoofers (included with the speakers are generic Belden equivalents). During public demonstrations, Avantgarde uses MFE cords. So do I..

The individual listener must spend time to arrive at the most pleasing final tuning. Here the assistance of a good dealer is very helpful, and Avantgarde goes through pains to assure quality representation. This selectivity isn't arrogance or snobbery but plain insistence that prospective dealers understand and practice Avantgarde's philosophy - a motto and concern I consider very legitimate.

My personal loudspeaker cables are HMS Gran Finale which led me to subsequently request matching custom jumpers from the same firm, a good move that mitigated the occasional hardening of the silver cables. Suitably impressed, I was ready.

As was the associated amplifier. My valve bias is well known. Considering the technical specs of these horns -- sensitivity of 104dB/1w/1m, nominal 8-ohm impedance, suggested amplifier power greater than 10 watts -- the unusually high speaker efficiency made my thermionic 15-watt Vaic 300-B stereo amplifier rating the perfect candidate. Although, topnotch transistor amps work equally well with all Avantgarde Acoustic speaker systems..

Incidentally, the DUO subs (as well as all other low-frequency transducers from this firm) offer XLR and RCA low-level inputs while the recommended connection remains speaker-level. Height adjustments of the horns along the triple pole frame -- with the help of a third hand, certainly -- is quick and uncomplicated. This flexibility isn't casual but rather affords top-shelf calibration of the equipment to engender high anticipation. No surprise. After all, music is an emotional subject.
The music

As a Jazz musician, I continuously survey the scene. A current release is Water Falls by Sara K who's presently on a German tour. I'll attend. After all, without knowing how an instrument or artist sounds, how can I report on reproduction? Hence our Editorial mandate to "attend, listen, know what you're talking about". Incidentally, this is Sara's first album not produced by the US Chesky label. Günter Pauler's classy Studio Stockfisch did the honors to deliver on Sara's high standards [in-akustik, SFR 357.6025.2]. The disc kicks off with a live street performance by a Ukrainian accordeonist and was captured on a Nagra-D recorder, via twin TLM-50 Neumann microphones on tall mic trees in an expanded A/B array. Palvyk Volodymyr probably didn't relate the sight of said setup to a recording session but broke into "Chattanooga Choo Choo" regardless each time Sara appeared.


This piece -- replete with untranslated dialogue -- ties directly to the first cut titled "Running Away From You". The special timbre of Sara K.s chosen instrument? A 4-string Pimentel guitar with nylon strings the size of knitting needles. Accompanied by a 6-string steel string guitar and a 5-string Börjes electrical bass, underlined with soprano sax and a bass clarinet at the wonderfully fading conclusion, this is the type of music I haven't heard reproduced in the kind of fashion the DUO pulled off. It's clearly not for the typical bring-his-own-pillow garden party crasher. On track 2 "Turned In My Upside Down", you hear the belt-driven mechanical grating of the hornspeakers built into the Hammond B-3 organ's Leslie cabinet -as resolute as though standing right next to it. Granted, part of this was due to the producer's trickery to create optimum signal separation from the belt drive's accompanying ruckus by recording the Leslie in a separate room with two microphones. Makes you question the intention since only a Hammond B-3 is capable of such gorgeously etheric timbre.

The following track "The Painter" is reminiscent of Gerhswin. Violin and cello in unison with the vocals, fretless electric and upright basses intermixed? No problem. "Listen intently and I shall reveal all to you" - that's how the DUO responded to this intricate challenge. The album's eponymous 5th track sports a dreamlike, nearly surreal sonic montage. The inner life of a piano's felt dampers and mechanical pedal sounds is rendered in extreme specificity by the use of twin miniature mikes attached directly to the sounding board. Key localization during descending runs was thus centimeter-precise. The shamanic frame drum was full of energy and abyssmally extended, accompanied by a distinct clicking impulse from the detensioned skin. Such drum whacks readily disqualify lesser amplifier and loudspeakers.

Not so the DUO. Its combination of spherical horns and active subwoofers compels me to describe them, without exaggeration, as truly spectacular. On track 9, the direct-to-disc mastering resolution turned rather eerie, with nearly scary dynamic range. A 12-string guitar's octave-doublers are mounted onto a standard 6-string to create a harpsichord-type timbre. Twin steel-string guitars, con arco double bass (note those sonorously vibrating strings) and udu (an Indian clay drum) conjoin with Sara's voice ... hey hey hey!

Switch to mid-80s Supertramp. Their "Breakfast in America" sold 18 Million copies. "Safri-Duo" (an unwitting analogy to "saftige [juicy] DUO" perhaps) catered to the high-excursion, quadruple 10-inch sealed woofers with its synthetic percussion and drum madness rum amok. The subwoofers' stoic nonchalance didn't even flinch regardless of programme material. During occasional output excesses (when my wife was absent and I "boss"), I had to declare premature defeat long before the DUOs deigned to compress.

Conclusion

Never before has a loudspeaker system impressed like this. Never before has music (and to list all I tested would far exceed this review's scope) touched me with such enchanting powers of authenticity as when played back over the DUO. Its strengths lie undoubtedly in this nearly hypnotic, distinctly addictive mien that doesn't suffer the faintest hint of coloration. Especially the critical midrange deserves highest praise. The sound in a nutshell? Pure music in all its facets! The excitement of live music is this system's core signature, thus fulfilling my personal requirements for listening to music in the first place. Accordingly, DUO fantastico: "No màs buscando" - no more searching.

Ancillaries:

Turntable: Transrotor Rotary with filtered powersupply, ceramic sphere, High-Tec oil
Arm: SME 3009
Cartridge: Ortofon Kontrapunkt A
Phono cable: HMS Gran Finale, RCA-to-RCA
Phonostage: Lehman Black Cube
Interconnect: HMS Gran Finale
CDP: TEAC VRDS 25x
Preamp: MFE Tube One
Amplifiers: Vaic 300-B stereo, Audiomat Duo (NOS GE 6550, critically selected predrivers)
Loudspeaker: Avantgarde Acoustic DUO
Loudspeaker cable: HMS Gran Finale 3-meter single wire
Subwoofer connection: HMS Gran Finale TOP Match interconnect
Power cords: MFE und XLO-10ER, home brew power strip (ferrite parallel-coupled massive copper buss bar power distribution), HMS twin-Schuko wall receptacle, discrete 20-amp line
Accessories: "Solida" rack, shelves and various cones and aluminum footers by Feines HiFi & S.O., further supports by Future SoundRack

Listening Environment

Rectangular room of 10 x 4 meters
Massive Ytong walls with 36cm mud cover, one side wall with windows and doors, one with central door.
Concrete ceiling with raw fiber paint. Rear wall covered with LP shelves. Front wall behind system covered in home-made absorbers. Floor carpet-covered, windows dressed, central sofa. The overall acoustics equal most other furnished rooms by being predominantly damped.