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Reviewers: Marja & Henk
Sources: CEC TL5100, Audio Note tube DAC, Philips DVP 5500S SACD/DVD player, Metronome CD3 Signature [in for review]
Preamp/integrated: TacT RCS 2.0 room control system; modified Audio Note Meishu with AVVT, JJ or KR Audio 300B output tubes
Speakers: Avantgarde Acoustic Duo internally wired with silver; Avantgarde Acoustic Solo in HT 2.0 setting; Audio Note AN/Jsp silver-wired; Tannoy Glenair [in for review]
Cables: Audio Note AN/Vx interconnects; Siltech Paris interconnects; Gizmo silver interconnect; Qunex 75 reference interconnect; Crystal Cable CrystalConnect Reference interconnect, CrystalDigit S/PDIF RCA/RCA and RCA/BNC, Y-cable, Crystal Cable Piccolo iPod to XLR, CrystalPower Reference AC-Eur/IEC; CrystalSpeak Reference, Audio Note AN-L, Gizmo silver LS cable; Virtual Dynamics Revelation power cords [in for review]
Power line conditioning: Omtec PowerControllers
Equipment racks: Solid Tech Radius
Sundry accessories: IAR carbon CD damper; Denson demagnetizer CD; Nespa #1; TacT RCS calibrated microphone and software; Exact Audio Copy software; Compaq server w/Windows Server 2003 and XP; wood, brass and aluminum cones and pyramids; Xitel surround processor; Manley Skipjack
Room treatment: complete set of Acoustic System Resonators; Gizmo's Harley Davidson cap
Review Component Retail: 6000 euros; $8,000
Contrary to many of our fellow music lovers cum audiophiles, we are very conservative. That is, over the last years we have never felt the urge to upgrade major audio equipment because the next CDP, DAC or amplifier was so much more satisfying than what we already owned. Over the years, a whole carload of the aforementioned devices have found a place in our listening room. On most occasions, we were happy to get back to our own set once the review had run its course. On few occasions only, there were almost tears when the call tags arrived.

Of course we did have our share of modifications to our equipment stack in those years. Being in the review business, we could promptly compare the results to the sound and emotional qualities of audio gear from almost any price range. An investment of a few hundred euros now and then for different tubes or capacitors in the DAC and amplifier did make the differences we were looking for and had desired -- learned to recognize -- from reviewed machinery far out of reach of our wallets.

Being satisfied with what we have assembled is part of the relaxed background against which we can now fully enjoy the music we play. There is no little devil telling us we should buy another so-and-so. If finances were unlimited, that would result in a complete and additional system for another room. But since that's not the case, what we have definitely stays. Conservative indeed.

The choice we made some seven years ago on the Avantgarde Acoustic Duo loudspeakers was based on many listening sessions over a long period of time. At that time we were quite happy with the Audio Note AN/Jsp. Its qualities to convey emotions was more than adequate. That is until we visited the Parisian Audio Note shop, Triode et Company, who also had Avantgarde Acoustics in their portfolio. The combination of the typical Audio Note way of handling the musical signal and the enormous directness of the German horns was mesmerizing. We both were love-struck after the first extensive listening session. After that we went back a couple of times for more listening confirmation. When the opportunity arose to finance a pair, we ordered them and have since been very happy with our big blue friends.

In the last couple of years, we've heard the Duo's big brother on many occasions - the Trio with Basshorns. We listened to these huge artworks for extended periods and around here it is no secret that they were The Materialistic Goal for us. If the house were bigger. If the price wasn't the problem. If this and if that. Still, we always came home to our Duos and were happy.

Then at CES 2005, Avantgarde Acoustic demonstrated their new Meta Primo. This model is positioned between the Duo and the Trio. It makes the performance of a Trio/Basshorn combination available in a much smaller footprint. The new speaker uses the tweeter from the Trio Omega with a special crossover; and a new midrange driver with an Alnico magnet. From the Basshorns, the Meta Primo borrows the concept of four horn-loaded active woofers with an amplifier per woofer pair. That demonstration reset our list of materialistic goals and entered the Meta Primo behind the full-swing Trio-Basshorn combination. Still the "If Then Else" reality that is our Duo got us grounded again. And happy still. Again.

Until Armin Krauss of Avantgarde notified us of an imminent upgrade to the Duos that would turn them into Duo Omegas. With this upgrade, both tweeter and midrange are replaced as are the tweeter crossover boards. The upgrade involves only a minor soldering and is fully retrofittable by the end user. Order the upgrade, perform the upgrade and return the old drivers to Avantgarde. The news got even better when Armin offered to send us an upgrade kit for review. That meant our 8-ohm, 104dB Duo was going to get turbo-charged into an 18-ohm, 107dB Duo Omega. Too good to be true?

Avantgarde horns are known for their qualities in the midrange. This area is the most important as human hearing is especially sensitive here. Speech including baby cries occur in this range. Ditto for the fundamental tones of most instruments. According to horn designer Matthias Ruff, the new midrange M2 Omega driver for the Duo Omega is an adapted advanced version of the standard Duo M2 8-ohm unit. In order to get a higher magnetic flow in the driver's air gap, Matthias left out the copper inlay that is usual attached to the pole piece. The pole piece is that part of the magnet assembly that protrudes from the donut-shaped motor.

The voice coil is wrapped around the pole piece. This construction leads to higher voice coil induction. In combination, a new cellulose dome resets the crossover point to the tweeter. To achieve the requisite increase of flux density and efficiency, the choice of an Alnico magnet -- the material of convention for such applications until the 60s -- was obvious. The designation Alnico derives from the materials used to form the magnet: Aluminum, Nickel and Cobalt. As the price of cobalt rose to stratospheric levels in the '60s, the much cheaper ceramic variants of magnetic materials invaded loudspeaker transducer manufacture. Besides being cheaper, ceramics were easier to work than the very hard and brittle Alnico which complicated manufacture and further penalized pricing. However, the difference in tone between a ceramic and Alnico-based driver is not subtle. Alnico is far more natural, organic and smoother.

Just altering the pole piece and switching to Alnico isn't all that's new for the Omega midrange. Avantgarde's diaphragm supplier had an idea for a velours damping effect -- VDE -- to be applied to the M2's cone. They asked Matthias to test a few samples. Unfortunately, those early samples failed his tests. Nevertheless, Matthias was intrigued by the idea and soon came up with why the tested cones failed. Closely working with the supplier and testing many different paper domes, he finally identified the right one. He envisioned that when the cone was covered with myriad micro hairs, the cone resonances would be tamed and high frequency distortions absorbed. Of course, the dome should match the new cone he'd need.

The mechanical high-pass frequency of the M2 midrange driver is set at 170Hz which eliminates electronic compensation to ensure a smooth handover to the Duo's subwoofer. On the upper end of the midrange driver's frequency range, the so-called CDC system takes care of a very controlled natural roll-off at 2000Hz. CDC is the Controlled Dispersion Characteristic, Avantgarde's means to limit operation to a predetermined range with a small chamber between throat horn and driver diaphragm.

This chamber's air volume acts as an acoustical low pass filter - a band-pass filter. All frequencies above the chamber's resonance are filtered at 6dB/octave. Together with the driver's own mechanical 6dB roll-off, the CDC adds up to an effective 2nd-order slope without any passive crossover components. Accordingly, the midrange driver is direct-coupled to the amplifier, lacking any passive components whatsoever.

In order to prevent the tweeter from going literally up in smoke, electronics are needed, however. For the Duo Omega, the tweeter becomes the very same used in the Trio Omega - the H3. The H3 has a 1-inch dome and Kapton voice coil former. The 6.5 lbs magnet -- massive for a tweeter -- is incredibly strong as we'd learn later. Coupled to the tweeter horn, this driver reaches 900Hz, well lower than the 2000Hz point of the midrange.

Even though the electronics in the passive tweeter network are kept to a minimum, a capacitor has to filter out the lower frequencies. The disadvantage of an ordinary capacitor in a circuit like a crossover is that every time the incoming musical signal changes polarity -- from the positive half of a sign wave to the negative half and vice versa -- the dielectric field charge inside the capacitor inverts as well though the dielectric material 'resists' this change. It holds the field at zero until sufficient voltage 'kicks' the field strength to rise again. Armin Krauss compared this delay mechanism with trying to slide a case of beer across a concrete floor.

Once it slides, you need less force to keep it moving but to get it going requires quite the push. Due to the fact that the musical signal is transmitted through the capacitor's electrical field, there will be a non-linearity caused by the dielectric's zero-crossing time shift. According to Avantgarde, the best way to fight the negative influences of this flip-flopping polarization of the dielectric field in the capacitor is to introduce a capacitor polarization circuit. This CPC then eliminates the timing distortion that the very sensitive horn system would merciless reveal. Though this time lag is very short, our ears do notice it.

Matthias Ruff designed the CPC with a DC bias voltage to create an unidirectional electric field. The special capacitor does not have to -- cannot -- change polarity. Its bias is far higher than the musical signal voltage will ever be. The Avantgarde capacitor is built up of multiple conductors instead of the usual two halves. The inner conductor is biased with 100 Volt DC.

Interestingly, this 100 Volt bias current is not derived from an external source. No battery or AC circuit are used. The music signal becomes the source for the 100 Volt current. Via the CPC module -- the red box on the crossover board shown at the beginning of the review -- the incoming musical signal is tapped by a low impedance transformer and then up-converted to the desired 100 volts.

So far for theory. Let's open the delivered boxes. As already mentioned, the upgrade involves a very limited amount of soldering. In fact, we received the pre-soldered kit's matte grey back covers for the driver tubes. In another box were the four new drivers, with the two mids cleverly fixed together to protect them from transit damage. The delicate domes of the new H3 tweeter drivers were protected with aluminum caps. One extra cap was included for use when the drivers are actually swapped out. Then there are the new CPC crossover boards. Here we see just the huge capacitor, the CPC module and the coil. A separate box contained the installation manual, a variety of screws and tools and two pairs of speaker cables. The speaker cables are Avantgarde's own - silver-plated copper coax. The tweeter is terminated with a FastOn connector. The overall impression is one of high quality throughout, from manual to packing material to contents.

Despite our IT background's usual MO, we RTFM'd. Yes, we Read The F* Manual. This was a good idea since we -- erroneously -- presumed that it was necessary to put each Duo on its back to detach the driver housings. Not. You just need a second pair of hands. You start the upgrade by switching off the subwoofer - not mentioned in the manual by the way. Then you detach all cables from the midrange and tweeter units.

Now unscrew the three bolts which secure the midrange unit to the upright poles. Here you need the second pair of hands. Lift the unit out of the rack and place it on the horn's flange. The lacquer on the horn is delicate so use a soft cloth underneath. To unsolder the wire, use a hot soldering station, not your lightweight circuit board iron. Next remove the three pieces of damping material. If you are not going to solder, you need some extra hands to hold the back cover while you unscrew the two nuts from the long threaded bolts that attach the housing shell to the horn itself. After unscrewing the bolts, the tube detaches. Our tube was somewhat sticky so we had to gently tap it before it came loose.

Now the old ceramic driver was accessible to detach its leads. With the provided tools, we removed the driver and MDF spacer ring. The new aluminum spacer ring took its place and the new driver followed suit. The difference between old and new driver is enormous. So is weight. Next we connected the new leads. When using the pre-soldered kit, extra hands are needed again as the back cover needs to be placed on the housing loosely and the housing put almost in place on the horn. While holding the housing a little above the horn, you attach the short cables to the driver. This makes using the pre-soldered back covers not the most convenient choice. Doing a little of your own soldering makes things much easier. Next the tube is lowered atop the horn and the nuts are fastened. Make sure that the rubber seal between housing and horn is in place and follow the manual's tip to use a little wash-up soap to make the placing smooth. In case of the solder kit, solder the wires to the WBT connectors on the back cover. Before re-attaching the back cover, reinsert the damping liners, then mount the midrange horn back into the rails.

The tweeter assembly follows. Here you don't need to take the unit off the rack. Just detach the back cover and unplug the wire from the crossover board. Put the back cover aside. Move to the front of the speaker and undo the four screws that hold the tweeter's mounting plate. It was a bit awkward detaching the screws as the turns you can make are limited even with the included 90-degree screw driver. Once the screws are detached, we could take out the little horn with the tweeter driver still attached to it. After removing the cable leads, we put the driver with its horn on a table.

With the delicate aluminum dome fully exposed, the driver is extremely vulnerable. So we put the extra aluminum back cover over the dome as quickly as possible. Then we turned the tweeter so that the front plate could be unscrewed. This front plate is then screwed to the new driver. Next we turned the new driver over and removed the protective back cover. Surprise. No shiny aluminum dome was staring at us but instead, a grey membrane. We plugged the connectors of the new lead to the tweeter, careful not to touch the dome in the process.

With four new washers and four new screws, we had a little trouble putting the new driver back in place at the front of the housing. The new magnet is really strong and aligning the four screws to the corresponding holes while keeping the spacers in place was not easy. That's because the magnet is very much attracted to the tube's mounting ring. If the spacers had a slightly smaller inner diameter, they would hold on to the screws, making the operation easier to perform.

At the table, we unscrewed the crossover board from the tweeter's back cover with the provided tool. Depending on the model -- or age -- of the Duo, there are different WBT terminals in use. With silver WBT terminal, you have to replace them for new ones that are 3 mm shorter to accommodate the new crossover board. Our terminals had the correct length but if you order an upgrade, find out which terminals you need.

The new crossover attached quickly to the back cover. When you attach the wire from the driver to the board, make sure that the new tweeter is connected in phase as opposed to the old one that was wired out of phase. Next make sure you lead the internal wire above the cross bar in the housing before connecting the cable to the crossover board. What remained now was to merely attach the back cover and repeat the exercise for the other side.

From unpacking, reading the manual, performing the upgrade and repacking the old drivers, it took us 3.5 hours. According to Armin Krauss, that's about the going average. Soldering or not makes little difference with regards to time. It's simply a question of what you feel
better about. When in doubt, you can always find someone to help you. You'll need an extra pair of hands anyway.

When the speakers were back at their customary spots and all cables re-attached, it was time for the first listening. Was the upgrade worth the anticipation, time and financial bill we'd be presented with if we decided to not revert to our old Duos? In one loud word, "Yes!". From the first tone, with the drivers cold out of the box, the difference was huge. Though the familiar house sound remains, the Omega offers more authority over details. The already very dynamic behavior is further heightened. We started with the volume attenuator set at about 1/3rd of the normal setting in anticipation of the raised system efficiency. With our 8-watt amp, we used only a minute fraction of available power. Roughly 88dB in the listening seat are achieved with just a slightly turned volume knob. Details never heard -- or better, recognized -- before were now so naturally available that our attention was completely absorbed. The need for an absolute silent playback system is naturally vital with 107dB speaker sensitivity. Every part in your equipment chain must accommodate this extreme requirement. Our system proved dead quiet with the Duo Omega. Strange in fact as with the old Duo, there was a slight hiss when we put our ears close in front of the tweeter. Now there was only perfect silence.

After playing the Duo Omega for about 100 hours, the drivers loosened up and dynamics and smoothness increased further. Where cymbals and other large brass instruments could at times sound nearly harsh before, the high overtone frequencies are now smooth and betray zero edginess or thinness. The handover between the horns is smoother. With saxophones -- on good recordings -- there is no hint of tin or brightness. Reed and metal just come together in what they really are, warm as the real temperature of the instrument.

As stated before, midrange frequencies are critical to human hearing. With the new Alnico driver, voices -- and not just female ones -- are more natural. Male vocals like spoken voice aren't compressed into nasal numbness. A male speaker has blown his nose and opened op sonically. For the amplifier on duty, the new 18-ohm impedance appears to remove the load altogether. Combine that with the extreme high sensitivity and the amplifier might think it's just idling while creating the most beautiful music for us.

The upgrade from Duo to Duo Omega worked out even better than we had hoped for. We now have more real music in the house which is effortless transmitted and completely free of constraints from the loudspeakers. The difference between the old Duo and the Omega is more then a small improvement. It is a major step towards Trio Omega level. That level is realistically approached. However, bass could still benefit from an upgrade as well. Now we have turned the volume of the subwoofers one notch down to get a satisfactory blend of the musical spectrum.

Is the upgrade worth the costs and work involved? A definite yes! Getting to this level is not possible unless you sell your old Duo and buy a Meta Primo instead. You always lose big selling. 50 to 70% or more is common. Then you have to reinvest in a brand-new pair of speakers at full retail. With the Omega option, you can hold on to your initial investment and simply add the cost of the upgrade alone. Spread it out over a few years and that's not a bad proposition at all. Therefore we would like to present Avantgarde Acoustic the Blue Moon Award for Sound Investment in the hornspeaker category.
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