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This review first appeared in the November 2013 issue of hi-end hifi magazine High Fidelity of Poland. You can also read it in its original Polish version here. We publish its English translation in a mutual syndication arrangement with publisher Wojciech Pacula. As is customary for our own articles, the writer's signature at review's end shows an e-mail address should you have questions or wish to send feedback. All images contained in this review are the property of High Fidelity or Avantgarde. - Ed

Reviewer: Wojciech Pacula
CD player: Ancient Audio Lektor Air V-edition
Phono preamplifier: RCM Audio Sensor Prelude IC
Cartridges: Miyajima Laboratory Shilabe & Kansui
Preamplifier: Ayon Audio Polaris III Signature with Regenerator power supply
Power amplifier: Soulution 710
Integrated amplifier/headphone amplifier: Leben CS300 XS Custom
Loudspeakers: Harbeth M40.1 Domestic + Acoustic Revive custom speaker stand
Headphones: Sennheiser HD800, AKG K701, Beyerdynamic DT-990 Pro 600Ω vintage, HifiMan HE6
Interconnects: CD/preamp Acrolink Mexcel 7N-DA6300, preamp/power amp Acrolink 8N-A2080III Evo
Speaker cable: Tara Labs Omega Onyx
Power cables (all equipment): Acrolink Mexcel 7N-PC9300
Power strip: Acoustic Revive RTP-4eu Ultimate
Stand: Base IV custom under all components
Resonance control: Finite Elemente Ceraball under CD player, Audio Revive RAF-48 platform under CD player and preamplifier, Pro Audio Bono PAB SE platform under Leben CS300 XS
Review component retail in Poland: €11'500/pr

The bottom panel of the electronics module mounted to the Zero 1 Pro’s rear baffle sports an identification plate. In addition to info about its place of manufacturing—Avantgarde’s large new factory in Reichenbach/Lautertal, Germany—we find a serial number. The pair which came to me after initial break-in at the factory and then the distributor was labeled ZERO.0008. This made it one of the first pairs ever assembled. The very first one went to the High End show in Munich earlier this year where it made a great impression. Awarded by us Best Sound High End 2013, these speakers are extraordinary. But it’s not the kind of extraordinariness we associate with peculiar high-end exotica. Rather it's a very real, technologically solid fusion of functions that integrate truly superb user friendliness. To arrive at such a conclusion of course requires that we first take a far closer look to learn what really hides behind these smooth black or white monoliths.

We ought to start with Avantgarde's brochure 'from the beginning'. The Zero 1 Pro is a horn-loaded three-way active speaker system. Each of its two horn-loaded drivers is powered by a separate 50-watt X50 amplifier. The woofer gets a powerful 400-watt class D Hypex module. The midrange and treble amps operate in pure class A with zero NFB and share the power supply of Avantgarde's standalone XA power amp. Power to them is heavily filtered and even the control system runs off a stabilized supply. The sensitivity of the midrange and tweeter drivers is a high 104dB but familiar figure from other models in this catalogue. Yet certain characteristics still are unique to this model.

First there's size. By definition hornspeakers are large. Their size can be scaled down within reason as reflected in the firm's Uno Fino yet classic full-range hornspeakers are from large to very large. By contrast the Zero 1 Pro appears like a true miracle with a front baffle almost the same as my stand-mounted Harbeth M40.1 maxi monitors. That alone is a great achievement. Yet it's when we stare at the Zero 1 from the side that we clutch our head and wonder where the heck the subwoofer enclosure has disapparated to. This speaker is no deeper than an Ikea bookshelf in its shipping carton. Yet these woofers are powerful 300mm beasts, boasting a -3dB point of 30Hz. Such miracles were made possible by harnessing the power of digital circuits.

At Munich I spoke with Armin Krauss whom you'd easily recognize. Each year during the Warsaw show he’s Avantgarde's chosen presenter who loves Rammstein at concert levels. I couldn’t help notice that describing their new Zero 1 project he spent most his time explaining their innovative system formula. As he put it, we are quite familiar with active speakers fed by a line-level signal straight off a preamp or variable source, then crossed over inside an active filter network to be amplified separately for each driver. The Zero 1 Pro differs already by accepting a digital signal which is processed in that domain before D/A converters dispatch it analog to the final amplifiers.

This speaker's active crossover is carried out in the digital domain. Avantgarde programmed a 64-bit FPGA for high response/phase precision down to 10Hz. Finite impulse response or FIR filters guarantee outstanding impulse response for all six channels of D/A conversion. The German engineers shaped their filters to achieve almost perfect phase characteristics which in the Pro version nets less than 5° of deviation and nearly absolute synchronicity. Digital filters usually run very steep slopes to most effectively limit overlap between drivers. Many designers and music enthusiasts believe that the best results really come from the shallowest of filters, i.e. a 1st-order slope at 6dB/octave. Avantgarde too subscribe to this view, hence their progressive slopes. At the crossover points 6dB slopes rise progressively until they hit 100dB steepness at the intended cut-off points.

All this makes the Zero 1 Pro into an active three-way with a DSP filter. It stands to reason that the input signal would be digital then and so it is. The entire DSP/amplification assembly lives in a cast aluminium enclosure set into the rear baffle and covered by a nice grille. From below we connect to this module via USB, Toslink, 2 x coax or AES/EBU, i.e. nearly all existing standards. If we want WLAN we connect via Toslink to a suitable receiver like Apple's AirPort Express.

The input signal feeds to only one speaker which serves as master. The other is slave and syncs up wirelessly via 16/44.1 transmission. During our conversation Armin devoted much time describing their wireless signal transfer and the measures they took to minimize distortion. It was a real priority to develop a proprietary 2.4GHz protocol. If like me you believe that nothing beats actual wire, an Ethernet cable can connect the speakers with each other instead which then automatically disables the wireless transmitter.

This speaker is available in two versions distinguished only by software. The standard Zero 1 sells for €9'900/pr, the Pro demands €11'500. This reflects where many of today's real costs are – in software R&D. The costlier version is meant for no-compromise applications and employs 'minimum phase' software for extremely low phase shift. This review deals with the Pro version.