Avantgarde Reviews: DUO 2.0 - Steven Rochlin, Ultimate Audio

Isn't it ironic how music reproduction has come full circle?

Vinyl records, single-ended tube amplifiers and horn loudspeakers are all experiencing a renaissance and receiving rave reviews around the world. This of course begs the question: have we been led down the garden path by the 'scope jockeys? Why is it that with all our technological advances, hornspeakers using paper cone drivers are winning new converts daily due to their low distortion? Is this old design used in the new Avantgarde Duo 2.0 horn speakers the newest "new" in musical enjoyment?

Careful Setup is Key

Like any good high-end speaker, the Duos demand careful attention to placement and ancillary electronics. One of the first decisions when setting up the Duos is whether or not to use jumpers. Why do you need jumpers with the Duos? The tweeter, midrange and self-powered subwoofer all have separate loudspeaker wire terminals. You would have to tri-wire the system unless jumper cables were used.

Word on the street was that the Nirvana Audio Avantgarde Jumpers were better sounding than the stock silver jumper wires (AVG now actually provides oxygen-free copper jumpers - ed.) - and my experience confirms the scuttlebutt. The Nirvana jumpers consist of black mesh-encased, high-purity, 18-gauge and 14-gauge copper wire. The 14-gauge connects to the tweeter while the shielded 18-gauge goes to the subwoofer amplifier. Out of my stable of speaker cables, Nirvana Audio's S-L loudspeaker wire also proved to be the best, bringing out the speaker's clarity and harmonic rightness.

Four different amplifiers were used with the Duos during the course of this review. Out of the quartet, the 47 Laboratories Gaincard mated best with the Duo 2.0s. They weren't overblown and lush as with the WE300B amplifier or as sterile as with many lower-priced solid-state designs. And if there's one thing the Duos will let you know, it's the quality of the equipment it's mated to. (In retrospect, I lamented returning the Wavelength Audio Mercurcy amplifiers reviewed in the Summer 2000 issue of Ultimate Audio, for they would have been a match made in heaven.) Other amplifiers that saw service included the VAC Avatar integrated amplifier, Doc Bottlehead's Paraglow and the FASE Nimisis.

The new Duo 2.0s are far more demanding of upstream components than the older Avantgarde horns. For instance, the Avantgarde Acoustic Unos were quite happy with the admittedly long-in-the-tooth Western Electric-equipped WE300B monoblocks. It seems the WE300B's slightly rolled-off highs helped to smooth out the subjectively brighter sound of the Unos. In contrast, the WE300B was too rolled off and the bass too muddy with the new Duos. It is when you get to play with the Duo (or electrostatic loudspeaker) "microscope" that you truly realize the good, the bad... and the ugly.

It was much easier to position the Duo 2.0 (and also the Uno 2.0) than their earlier versions. While the first versions were highly transparent, finding a balance between positioning and overall smooth frequency response -- because the speaker had a glint of brightness, --was an affair unto itself. It's also worth mentioning that the new SUB225 CTRL PRO subwoofers are far faster and smoother than earlier efforts.

Finally, I employed a tweak suggested by reader Kurt Strain. First, I laid the speaker system on its back to allow easier angling of the top-mounted midrange. Next, I loosened the bolts connecting the woofer, tweeter and midrange modules. Finally, the midrange unit was lowered by one hole; the end result was that the midrange module was angled slightly downwards when the speaker was returned to the upright position. (An additional note: some may also need to lower the tweeter module by one hole on the mounting bracket - though it wasn't necessary in my case.) The upshot of this exercise? Angling the midrange driver virtually eliminated the speakers' vertically stretched image height.

Technical Highlights

Avantgarde Acoustic chose the simplest route to sonic purity. They combined in the Duos a time-proven spherical horn with first-rate, high-sensitivity, custom-made drivers. Each horn driver moves apprximately one tenth the distance of normal non-horn designs, resulting in vanishingly low distortion levels. In addition, there are virtually no crossover parts interfering with the music. In fact, the midrange driver uses no crossover at all!

Finally, a spherical horn has a controlled dispersion pattern - and therefore approximately 85% of the sound is directed to the listening position. While horn-loaded highs and midrange do not require super-sized horns, a horn-loaded bass system would be inherently large (refrigerator-sized). Therefore, with the Duos the designers chose another method to better accomodoate the home listener.

As for the drivers themselves: the tweeter consists of a specially designed 1-inch titanium dome (the same driver used in Avantgarde's top-of-the-line Trio). In the midrange, the Duo 2.0 uses a 7-inch cone plus a 4.5" center dome (dust cap) that can be seen when looking at the front of the midrange horn. The self-powered SUB225 CTRL PRO subwoofer consists of two Avantgarde 10T300 drivers that use a 10-inch driver incorporating a 3-inch voice coil and high-energy 15-pound magnet structure. Mating non-horn subs with these loudspeakers is every bit the challenge faced when marrying cone subwoofers with panel/electrostatic loudspeakers! In short, you need an extremely fast cone driver. If the subwoofers lag behind the speed of the horns, then what's left is a discontinuous, unsatisfactorily unmusical experience.

Another unusual aspect of the Duo's subwoofer drivers is the use of special paper pulp, instead of more conventional paper cones. During the course of manufacturing, this paper pulp passes through a special sieve followed by gentle air drying. The excess materials drip through the purpose-built sieve so that a special irregularly structured surface appears on the rear of the cone. Avantgarde Acoustic claims this irregular surface provides "incredible stiffness and acoustical neutrality and eliminates harmonic distortion and interference in the upper frequency range". The subwoofer comes with a 200-watt amplifier that powers both 10-inch drivers. Additional circuitry is used that continuously controls the velocity of both drivers' movements and reduces speaker distortion.

Sound the Horns!

The Avantgarde Acoustic Duo 2.0 replaced the smaller Avantgarde Acoustic Uno 2.0 - my current reference speaker. While both speakers share the same subwoofer, the Duo uses a larger midrange horn and improved tweeter. My main reservation with the Unos had to do with the blending of the midrange and bass. The Uno's midrange response didn't seem to extend low enough - and as a result there was a frequency response dip where the lower midrange mated with the subwoofers. While the Uno's overall clarity and speed was neck-and-neck with the best panels/electrostatics, there was a lack of smoothness where the bass meets the midrange

My hope was that the larger midrange unit of the Duos would go a long way toward solving this problem. To test this hypothesis, I went back and forth several times between the Duos and the Unos to verify my findings.

First up was Chesky Records' recent release, The Agnostic (CD 202). This minimally miked, audiophile-quality recording beautifully captures the sound of a full-scale orchestra with chorus and pipe organ - all recorded with the latest in 24-bit/96-kHz digital technology. This Chesky recording offers an outstanding reference for the low-level resolution of a piece of gear while also providing a great dynamic workout. Dynamics on The Agnostic run the gamut from eerily quiet to full-scale climaxes - and it's a test that the Duos passed with flying colors. Individual voices in the chorus were easily heard while the grand scale of dynamics was also captured. Imagine the seped of electrostatics, yet without their general dynamic limitations.

Although guilty at times of playing music at high volume levels, I find that many loudspeakers compress dynamics at lower auditory levels or in the louder passages. While the Duos do not have the speed of the finest electrostatcis, they come mighty close - and without the dynamic constraints of smaller electrostatics. This seemed especially true in the lower midrange where the Duo showed its superiority to the Unos.

In my experience, only the finest systems are able to reproduce the acoustics of this wide and deep hall and the Duos effortlessly filled my room with hall "sounds". The ambience and timing of the reflected sounds a hall provides are an essential part of the overall musical experience. The Duos really stood out when it came time to resolving subtle details. Properly sized imaging (not fake pinpoints) and complete rendition of overall soundstaging was left bare for my enjoyment and was improved over the Unos.

The Duo hornspeakers also proved more correct harmonically. My longing for better lower midrange support was definitely satisfied. Still, I felt that the Unos subjectively had a touch more clarity in some of the more dynamic passages. Could I be mistaken?

Next up was Willie Nelson's incredible Stardust album (CBS Master Sound half-speed mastered vinyl HC 45305). Willie's vocals were so clean and open-sounding that on "September Song" one could, with closed eyes, suspend disbelief if only for a moment. But even that doesn't adequately describe the sound. There was more than just clarity: there was flesh 'n' blood sound. Willie was in the room with me. While clarity and all that goes with it is a noble goal, in some speakers it comes at the expense of stripping away the soul of the music. In a musician's sense, it is the difference between playing the notes correctly and playing the music.

An aside: during the course of the review, my music-loving, audiophile parents dropped by and listened to the Duos. My father, who has quite an impressive system himself and has also heard some of the greatest musicians live, is not easily impressed. But after playing everything from deep pipe organ notes -- clearly (E. Power Biggs,if you must know) and easily energizing the room -- to the mass orchestral attack of Sheffield Lab's direct-to-disc vinyl recording of Wagner's Die Walkure: Ride of the Valkyries (LAB 7), I needed a crowbar to remove him from my listenig chair!

The older Avantgarde horns were somewhat lacking in the area of low frequency control and integration. This has been markedly improved in the new Duos as was evidenced by their performance when faced with reproducing something like Prodigy's Fat of the Land (Maverick 9 46606-2). For those unfamiliar with this recording, there are pulsating fast 32nd notes in the bass region. Imagine a normal rock song, which is 1-2-3-4. Now, in the same amount of time, instead of four beats make it 32. Very fast! While this is not something one would ever normally hear in acoustic music, it will easily show whether a subwoofer will be fast and clean, or simply fall on its face with slow, tubby tones.

The SUB225 CTRL PRO seemed to keep right up with the music until we reached levels louder than your typical dance club or rock concert. Then, it seemed, they simply ran out of juice while the horns could keep going a bit louder. While one could criticize the subs for not being able to obtain the same volume limits of the horns, how loud do I really want my music to go?

The challenge

One area that proved more of a struggle than others with the Duos was transparency. Compared to the Unos, the Duos seemed not quite as transparent. I ended up reinstalling the Unos, letting them settle in for a couple of days - and then going back to the aforementioned recordings. Re-listening to the same packages, I realized that the Duos weren't actually less transparent - the slightly attenuated midrange and highs gave the Unos the impression of being more transparent!

If you have had the opportunity, try using a truly transparent equalizer such as the Z-Systems rdp-1. It's quite easy to add a few dB to the upper midrange, and at the same time, sllightly lower the midbass. Presto-chango: you have better imaging and added clarity. (This is a neat treat trick that works for quite a few audiophile loudspeaker designs including the Lowther.) This also happens to be an area where many rooms have problems which affect the sound of speakers.

The Roundup

There's no denying that both Avantgarde Acoustic hornspeakers are exceptional performers. Going from the Unos to the Duos is like going from the Ferrari F40 to the F50. While the F40 is known to be a little twitchy yet excellent, the F50 is easier to drive around the track and adds to the F40's already impressive track record. The Duo's upper octaves are smoother than the Uno's - and at the same time, there's better extension and integration of the lower midrange/upper bass region. Where this comes into play: you can lower the crossover point where the self-powered subwoofer meets the midrange's output. For those looking for the speed of electrostatic/panel loudspeakers, yet with the easy drive and dynamics of horns, the Avantgarde Acoustic Duos should make your must-audition shortlist.

Steven Rochlin, Ultimate Audio, Winter 2001, VOl.4, No.4