July / August 2005


Avantgarde Acoustic Duo
Honing In On The Horn Sound... Or Lack Thereof!
Review By Steven R. Rochlin

  Why is it that music reproduction has come full circle? Vinyl records, single-ended tube amplifiers and horn loudspeakers are getting rave reviews throughout the world. After all, the new millennium is upon us! Has new computer technology lead us on the wrong path to audio nirvana? Solid-state amplification, high technology Aerogel loudspeaker drivers and carbon fiber interconnects are all new savoir-faire. Have the scope jockeys been exposed to too much CRT radiation? Why is it that, with all our technological know-how, horn loudspeakers using paper cone drivers seem to produce among the lowest distortion and possibly the highest in musical enjoyment?

The Challenge!
Like single-ended tubes, what was old is new again. Music reproduction has come full circle. This includes the longing for analog vinyl in this SACD/DVD-Audio "state-of-the-art" world. But that is another review, eh? Avantgarde Acoustics wisely chose the simplest way of proving the highest purity in design. Use a time-proven spherical horn with first-rate, high sensitivity custom made drivers. The low distortion levels produced from the Avantgarde Acoustic Duo 2.0 is due to each horn driver moves approximately a tenth of normal, non-horn designs. Another reason is that there are virtually no crossover parts interfering with the music. In fact the midrange driver uses no crossover at all!

Lastly, 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 like the aforementioned Lowthers). Therefore another method was chosen to better accommodate the home listener.

It Is All In The Details
As for the drivers themselves, the tweeter employs a specially designed 1-inch titanium dome. This is the same driver that is used in their top-of-the-line Trio. The Duo 2.0 midrange driver consists of a 7-inch come with a 4.5 center dome (dust cap) that can be seen when looking at the front of the midrange horn. As for the self-powered SUB225 CTRL PRO subwoofer, two Avantgarde 10T300 drivers that each employs a 10-inch driver with 3-inch voice coil with a high-energy 15 lbs. magnet structure. Mating non-horn subs with these loudspeakers was a challenge, as, like mating cone subwoofers with panel/electrostatic loudspeakers, you need cone drivers that are extremely fast acting. If the subwoofers lagged behind the speed of the horns then a discontinuous, unsatisfactory unmusical experience is the result.

Instead of using conventional paper cones, the 10T300 drivers use special paper-pulp that is passed through a special sieve and then gently air-dried. The excess materials drip through the purpose-built sieve so that a special irregular structured surface appears on the rear of the cone. Avantgarde Acoustic claims this irregular surface provides "incredible stiffness and acoustical neutrality, thus eliminating harmonic distortions and interference in the upper frequency range".

The included 200-watt amplifier powers both 10-inch drivers. Both RCA and XLR preamplification inputs are augmented by loudspeaker inputs for flexibility for any system. The phase is adjustable as is the crossover frequency and volume output (lower knobs). An additional internal circuitry continuously controls the velocity of both drivers' movements. This circuitry promises lower distortions while insuring the loudspeakers are reproducing the proper signal. Another benefit of this design is that the subwoofer system itself is 100dB/W/m sensitive in this 11.8 x 21.7 x 21.7 (WxHxD in inches) enclosure weighing in at approximately 100 lbs.

Careful Setup Is Key
Word on the street was that the Nirvana Avantgarde Jumpers ($400) would give the best in music reproduction over the stock silver jumper wires. Why do you need jumper wires? As the tweeter, midrange and self-powered subwoofer have loudspeaker wire terminals, one would need to tri-wire this system unless jumper wires were used. The Nirvana jumpers consist of a black mesh encased 18 gauge and 14-gauge copper wire of high purity. The 14-gauge goes to the tweeter while the shielded 18-gauge goes to the subwoofer amplifier. During this review I also felt a single run of Nirvana S-L loudspeaker wire worked best overall for clarity and harmonic rightness. As for amplification, and goodness knows I have about five different choices here during this review, the 47 Labs Gaincard and Wavelength Audio Cardinal amplifiers were excellent matches.

I found that positioning the Duo 2.0 (or the Uno 2.0 version also on hand) was not as finicky as their first, version 1.0, counterparts. While the first versions were highly transparent, setting them up was a challenge as finding a balance between positioning and overall smooth frequency response was an affair unto itself. The new PRO subwoofers are leagues ahead of their original counterparts. The originals were simply not as fast, nor as smooth as the new SUB225 CTRL PRO.

Lastly, a tweak I learnt from the great Kurt Strain, wise man of audio on the internet,  was to angle the top-mounted midrange unit by laying the speaker system on it's back. Then loosen bolts that connect the woofer, tweeter and midrange modules. Then lower the front of the bolts on the midrange unit by one hole so that when the unit is standing up, the midrange module is angled slightly downward. While I did not need to do this, you may need to lower the tweeter module down one set of holes on the mounting brackets.

Sound the Horns!
The Avantgarde Acoustic Duo 2.0 replaced my reference Avantgarde Acoustic lower line Uno 2.0. While the same subwoofer was employed, the Duo offers a larger midrange unit and improved tweeter. My main gripe with the Unos was that their midrange seemed to not go low enough which left a frequency dip where the lower midrange converged with the subwoofers. While the overall clarity and speed was neck in neck (to my ears in my system) with the best panels/electrostatics, the lack of smoothness where the bass meets the midrange was able to be overlooked to a great extent yet still audibly present. My hopes were that the Duos, with their larger midrange unit, would solve this. My review took a great deal of time as there was a need to replace the Duos with the Unos and then back to the Duos again to verify my findings. As the only reviewer to have both units available at the same time, let alone the only reviewer who has had the privilege of both units, there was a need to insure my findings.

First up for critical listening was Chesky Records new CD titled The Agnostic [CD202]. This wonderful orchestra with chorus and pipe organ was audiophile quality with minimal microphone techniques and recorded with 24-bit/96kHz digital technologies. The dynamics go from eerily quiet to full intensity. Only the best systems will be able to decipher the wide and deep hall with its natural acoustics. The Duos are incredibly articulate at providing wide dynamics. Individual voices in the chorus could be clearly heard while the grand scale of dynamics was easy to follow. Imagine the speed of electrostatics yet without their general dynamic limitations. While I am guilty, at times, of playing music at higher than normal volume levels, there seems to be a touch of compression with some loudspeakers either in the lower auditory levels or louder sections. While we might not be talking the great speed of the best electrostatics, it is close yet without the dynamic constraints smaller electrostatics provide. This seemed especially true is the lower midrange where the Duo truly showed its superiority to the Unos.

The Duos seemed to effortlessly fill the room with hall "sounds". The ambience and timing of the reflected sounds a hall provides is a good part in the overall musical experience. The 47 Laboratories Gaincard and also the Wavelength Audio Cardinal really mated well with the Duos in this regard as compared to other amplifiers in my humble abode. If there is one thing the Duos will certainly let you know, it is the quality of the equipment it is mated to. This Chesky recording offers a reviewer such as myself a real reference for the low level resolution of a piece of gear while also getting a great dynamic workout. The Duos handled everything extremely well and I was especially pleased with the clarity of the subtle details. Properly sized imaging (not fake pinpoints) and complete rendition of overall soundstaging was left bare for my enjoyment was improved over the Unos. The Duo hornspeakers were more harmonically correct than the Unos too. My concerns for better lower midrange support from the Unos were definitely answered with the Duos. Still, I felt that the Unos subjectively had a touch more clarity in some of the louder passages. Could I be mistaken? Read on...

Next up was the incredible Willie Nelson Stardust on CBS Master Sound Half-Speed mastered vinyl [HC 45305]. The clarity of Willie Nelson's vocals on the song "September Song" was such that with eyes closed there was more than just clarity, there was body and flesh n' blood sound that put Willie in the room. Clarity is good and all that goes with it, yet there is a point to where some speakers seem to have it at the expense of striping away the soul of the music. In a musician's sense, it is the difference between playing the notes well, or playing the music. In fact during this review process my music loving audiophile parents stopped by for a listen. They both sat in proper listening position and Willie sang his soul. Both my parents were so moved by the music that tears filled their eyes.  My dad, who got me hooked on music and music reproduction long ago, also heard some pipe organ (E. Power Biggs if you must know) and Sheffield Lab's direct disc vinyl recording Wagner Die Walküre: Ride of the Valkyries [LAB 7]. While my father has an impressive system himself and has been to more live concerts performed by the greatest musicians over the past many decades than I care to begin to mention, he was truly impressed. From the deep pipe organ notes clearly and easily energizing the room to the mass orchestra attack of the Sheffield Lab recording, the man not easily impressed needed a crowbar to be removed from my listening chair! Let us get back to Willie Nelson.

The one thing I was having a hard time with was the possibility of a slightly diminished transparency in sound of the Duos as compared to the Unos. So there I found myself removing the Duos out of the room and reinstalling the Unos. Let then settle in for a few days and listened to Willie, Wagner and the Chesky Records recordings very carefully. Then I removed the Unos and brought back in the Duos. Listened to the same musical passages and realized that it was not that the Unos were less transparent; it was the deceiving nature of slightly augmented midrange and highs! If you have had the opportunity to use a truly transparent equalizer (i.e. the Z-Systems rdp-1 as in Ultimate Audio Volume 2, Number 1) you can easily add a few dB of upper midrange and slightly lower the midbass and presto change-o, you seem to have better imaging and added clarity. This is a neat trick that seems to find its way into quite a few audiophile loudspeaker designs... including the Lowther. While it is hard to define how much the Lowther augments the 1kHz to 2kHz range as there are more cabinet designs and super tweaks to reduce the frequency peak, careful listening to a truly smooth frequency response design will allow one to know the truth.

Another caveat of the Duo is in mating it upstream equipment. While the Avantgarde Acoustic Uno was happy with my few years old Western Electric WE300B, it seems the slightly rolled off highs of the WE300B helped to smooth out the subjective brighter sound. Naturally other 300B variants (mesh plates) were a better match. It is when you get to the Duo, or electrostatic loudspeaker "microscope" is when you truly realize the good, the bad... and the ugly.

Speaking of ugly, I gave the subwoofers a good workout as the compact disc Prodigy Fat of the Land  [Maverick 9 46606-2] went through its paces. For those unfamiliar with this recording, there are pulsating fast 32^nd notes in the bass region. Imagine normal rock song, which is 1-2-3-4. Now in the same amount of time, yet instead of four beats make it 32 beats. That is eight beats to each single beat you previously imagined. 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 it's face with a slow tubby tones. The SUB225 CTRL PRO seemed to keep right up with the music until we reached louder than your typical dance club or rock concert levels. 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 self-powered subwoofer, how loud do I want my music to really go?

Spherically Speaking
To round all this up, both Avantgarde Acoustic hornspeakers are amazing. Even after hearing the Duos it is like going from the Ferrari F40 to the Enzo. While the F40 is known to be a little twitchy yet excellent and raw, the Enzo is easier to drive around the track and adds to the F40's already impressive performance (yes, I have to add something about Ferrari in every article I write). The Duo's highs seem smoother than the Unos and also add better support to the lower midrange frequencies. An added benefit of this is that you can lower the crossover point where the self-powered subwoofer meets the midrange's output. Thanks again to Kurt Strain for the angled midrange trick. Worked like a charm to virtually eliminate vertically stretched imaging. For those looking for the speed of electrostatic/panel loudspeakers yet with the easy of drive and dynamics of horns, the Avantgarde Acoustic Duos should make your very short list of must audition. Of course in the end what really matters is that you...

Enjoy the Music,

Steven R. Rochlin

Specifications
Type: Three-way full frequency loudspeaker with horn-loaded tweeter and midrange. Self-powered dynamic driver bass.

Frequency Response
    Horn section 170 Hz to 20 kHz 
    Pro 225 subwoofer 22 to 200 Hz

Power Handling:150 watts
Sensitivity: >103dB/W/m
Nominal Impedance: 8 Ohm
Recommended Power: >5 Watts
Overall Dimensions: 28 x 26.8 x 61 (WxDxH in inches)

Warrantee: 10 years for material fatigue, five (5) years on the lacquer finish and one (1) year on the electronics.

Price:
Duo (2.0) - ABS White with Nextel 225 CTRL Subwoofers
$14,470 + $325 shipping

Duo (2.1) - Custom Automotive Metallic Lacquer Finish (Blue, Red, Green, Silver, Charcoal, Pearlescent White) with Nextel 225 CTRL Subwoofers
$15,470 + $325 shipping

Duo (2.2) - Custom Automotive Metallic Lacquer Finish, with Matching Lacquer Finish 225 CTRL Subwoofers
$16,470 + $325 shipping

Company Information
Avantgarde Acoustic GmbH
Nibelungenstr. 349
D-64686 Lautertal-Reichenbach
Germany

Voice: 0049/6254 306-100
Fax: 0049/6254 306-109
Website: www.Avantgarde-Acoustic.de