Floor Loudspeaker Reviews

Active speakers make sense. The amplifiers, crossovers, and drivers are designed as a unit, so the design isn't compromised by the need to interface with components with unknown electrical or acoustical characteristics (except for the room, and that can't be helped). Concurrent design and testing of the various pieces can result in an integrated, through-designed system. Plus, the elegant simplicity that active speakers bring to a system just appeals to me.

Like many audiophiles, I've found myself intrigued by the variety of approaches that are taken to achieve the same goals: point source, line source, panels, horns. Whenever I've heard horns paired with a flea-powered amp, the dynamics have always impressed. I've consistently heard a jump factor that makes music feel remarkably alive. The combination of these two traits, though—horns plus active—is quite rare.

Another thing I've been thinking about lately is how rapidly computer technology is making everything more capable and at the same time less intrusive and easier to achieve. In hi-fi, streaming is a fine example, or network-attached storage stashed in a back room but available at your fingertips. I've been wondering when I'd see a DSP system that's affordable, useable, and capable of fixing the issues with my room without too much complication. Some great solutions are out there now, but I haven't tried them yet.

A pair of speakers just showed up at my doorstep that seems to check all these boxes—it certainly checks the first two, and it may prove in an audition to address others. The side of the box says "Avantgarde Duo SD iTRON." It's a fully active horn system with novel crossovers and amplification and integrated DSP in the bass. The two-speaker system costs $65,350; a semipassive version costs $47,350. I'm eager to give the Duo SD iTRON a listen (footnote 1).

The Avantgarde Duo SD iTRON
The Duo SD iTRON is part of Avantgarde's generation 3 ("G3") product line, which consists, top to bottom, of the Trio, Mezzo, Duo, and Uno. All are available either fully active (with amplification for all channels) or semiactive, with passive higher frequencies but active bass.

The G3 models incorporate two new foundational capabilities. The first is the iTRON system, which lies at the heart of the fully active versions of all four models. iTRON is built around a device Avantgarde calls it a voltage–current converter and not an amplifier, presumably because with voltage in and current out, it isn't possible to specify gain. iTRON is sufficiently novel to be the subject of several US and German patents.

In Avantgarde's view, driving a speaker by running the desired, time-dependent current through its voice coil is an inherently better approach than imposing a voltage across the voice coil and letting the current respond. The obvious problem with the voltage drive approach is that the force on a voice coil is proportional to the current flowing through it, and for a given fixed voltage, the current depends on a complex impedance curve, varying in both magnitude and phase. What's more, as the voice coil moves, the inductance—hence the voltage vs current—changes. It's impossible for the current, ergo the acceleration of the voice coil, to respond immediately to changes in the input signal.

If current is controlled directly, impedance complexities have far less effect on the force exerted on the loudspeaker drivers. The result is better control over the diaphragm's motion, enhanced damping, and a reduction in distortion resulting from resonance and back EMF. With current drive (again in principle), the problem of thermal compression—the increase in the internal resistance of the voice coil with temperature—is also solved.

Why doesn't everyone do this? Avantgarde lists several very basic problems that must be overcome to make current drive work, like the fact that with a current-based device, there's nothing to inhibit current flow near a circuit resonance, plus a fundamental incompatibility with passive crossovers. Avantgarde is so convinced of the superiority of current drive that they've gone to great lengths to reengineer the loudspeaker to make it work, eliminating passive crossover components and ensuring that each driver is operated in a range in which it doesn't approach resonance. They do this with novel technologies with fancy names, including SphericLowCut and AirGate, which do what crossovers do but without capacitors or inductors (footnote 2). SphericLowCut uses the horns' natural bandwidth to roll off frequencies at the low end; AirGate is said to serve as a low-pass filter without putting any devices in the circuit path. All circuitry is fully balanced and differential.

One more point about the iTRON system: Despite the great effort Avantgarde expended to make their G3 speakers compatible with current drive, the passive versions remain fully compatible with old-school voltage-drive amplifiers, with phenomenal sensitivity.

The second change is the addition of DSP, integrated into the subwoofer's 500W class-D amplifier. Avantgarde describes it as a fully digital crossover. The gain can be set completely in the digital domain, using buttons on the subwoofer's rear panel. Other parameters can be controlled by a PC running Avantgarde's control software, "Avantgarde XD-Series Control." This software lets users set an overall gain, tailor the frequency dependence, and set the subwoofer's Low Pass Frequency, or crossover point. The system also provides two narrow-band filters that can be used to lower room-related peaks. The Control Center is an outstanding tool, a model for other manufacturers. It looks nice, feels nice, and is easy to understand and use, and Avantgarde made good decisions regarding its technical capabilities.

The speaker under review, the Duo SD iTRON, is Avantgarde's least expensive fully active single-woofer Duo; it sits between the smaller Uno and the more elaborate version of the Duo, the Duo GT. In creating the G3 lineup, Avantgarde started from a clean sheet of paper and brought all the models up to a common technological level that incorporates their latest technologies, nearly all of which are new.

The Duo is (oddly, considering the name) a three-way loudspeaker, with a horn tweeter, a midrange unit with a 27" spherical horn, and a dynamic (bass-reflex) woofer/subwoofer built into the main loudspeaker chassis and featuring a new driver, the XB12, which Avantgarde calls "probably the most powerful driver that has ever been developed for a large, horn-based bass system." The XB12 has a massive 6" motor structure and magnets said to produce magnetic flux density (it's refreshing to see a company use a correct technical description, even in their marketing materials) of 1.15 Tesla. It's driven by a 500W class-D amplifier with, as previously mentioned, DSP.

The midrange's 27" horn loads a 170mm dome midrange driver (dubbed Evolution XM2), with a dome membrane with a description that sounds so odd that all I can do is repeat Avantgarde's description. "Its new 'Soft-Mesh Compound' membrane uses a stable grid carcass as its structural foundation. The microscopic apertures of the grid are sealed with a proprietary synthetic elastomer coating. The combination of stable grid structure with a flexible lining effectively reduces partial resonances of the dome itself and absorbs distortions." Rigid and soft at the same time.

The tweeter is the same one used in the flagship Trio G3; it has a "lighter, annular diaphragm" that Avantgarde says extends to 28kHz. Both the tweeter and the midrange driver are driven by 100W zero-global-feedback "iTRON" voltage-to-current converters.

Except for the low-pass filter in the bass module, which is digital, all crossovers are analog but active, with no passive circuit components that would upset the iTRON drive. The drivers are "coplanar" to ensure proper time and phase alignment.

Setup part one: muscles and hand trucks
The first step of the Duo's setup was to convert a quarter-ton, garage-stall–sized stack of palletized cartons into two assembled speakers. This took time and muscle, but the process was straightforward, and the reward was obvious even before the music started playing: Visually, the Duos are stunning. The cabinet is finished in Gloss (Piano) Black; it's also available with a matte finish. The horns on this pair were "Red Giant," one of Avantgarde's Metallic High Gloss colors; I'd describe it as glossy, liquid maroon with an impossibly thick clearcoat layer with just a bit of metalflake mixed in. Simply stunning.

Setup part two: cables, cables, cables
The second half of setting up a speaker boils down to using your method of choice to position them wherever they work best. Let's be clear about one thing. As already mentioned, active loudspeakers have significant advantages. Ease of placement isn't one.

Far from being liberating, the Duo's active design reduced placement flexibility for the simple reason that, in addition to the usual speaker cables (which here are replaced with long balanced interconnects), you need two power cords per speaker, and the IEC connector for one of the two is some 3' off the floor. To place the Duos where my previous speakers had been would have required four AC cords, two of them 8'–10' and two about 15', plus a pair of 20'–25' balanced interconnects. My room has a lot of outlets, and I have a lot of cables accumulated over decades of reviewing—but not enough to provide total flexibility in Duo SD iTRON placement (footnote 3).

Given my cabling limitations, my options boiled down to two. Thanks to the Duo's setup flexibility, and in particular the built-in DSP, I was nevertheless able to achieve a more-than-satisfactory setup. The one I chose put the Duos about 4' 6" from the front wall and 3' 4" in from the sidewalls, leaving about 10' between them, center to center. My chair was 10' 6" further into the room, forming a slightly-taller-than-equilateral triangle. The Duos remained precisely vertical—not tilted back or forward—and my calibrated slouch put my head about midway between the midrange and tweeter horns.

Setup part three: listen and adjust
Even after all the pieces are in place, connected together, and plugged in, you're still a ways from being ready to listen optimally. Some work remains, but it's fun work. Just think of it: You're on the threshold of greatness, about to make $65,000 worth of speakers sound like a million bucks.

Step one is easy: Just set the overall gain to a level that works well with your source output and preamp. Gain is set via three toggle switches, which can be set at 0dB, ±1.5dB, ±3dB, and ±6dB, for a range of 21dB in 1.5dB steps. I found that a setting of 6dB worked well with the BAT VK-90 preamplifier I was using over the range of volumes I use.

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Footnote 1: RD reviewed the Avantgarde Uno Nano 15 years ago, commenting, "A compact horn loudspeaker. Isn't that an oxymoron, like jumbo shrimp, or military intelligence?"

Footnote 2: There are capacitors in the iTRON Duos, special ones. Avantgarde calls them "NatureCaps" and says that they're "extremely elaborate" with "solid, rolled-aluminum" electrodes and "a cellulose fibre compound impregnated with biological oils as the dielectric." To keep the dielectric's polarity from oscillating, each capacitor has a "small DC circuit" to "fix the magnetic alignment"; this is, I'm thinking, something like the DBS units employed by AudioQuest in higher-end cables.

Footnote 3: The Duo SD iTRON comes with four 3m power cords, though the well-worn boxes arrived at Brian's place without them; he would in any case have needed a longer pair. I asked US/Canada importer Angie Lisi whether dealers typically handle Avantgarde setup. All Avantgarde dealers are well-trained to set up Avantgarde speakers, but, Lisi said, "Most end users' joy is to do setups on their own, as it is a big part of the fun, and they know that support is available to them. . . . Avantgarde has also made it very simple, with the new easy access to their Subwoofer DSP amp management. It's like an 8-band graphic equalizer with Bass Gain, Bass Boost and LPF level adjustments and 2 filters. Very user friendly. Connect to your laptop and off you go."—Jim Austin