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Resolution first, bass definition second, soundstaging third. Each of those is stepped down. But the more surprising part is how much the Zero 1 Pro overlaps with Avantgarde's flagships. The first of these overlaps is tonality. Hornspeakers won't be mistaken for any others. Their strengths lie in the immediacy of energy transmission which is perceived as more accurately rendered textures, better dynamics and generally superior differentiation. Whilst their resolution isn't that impressive, selectivity clocks far higher. The lynch pinch however is the midrange. Were classic speakers to sound similar, I'd pick out an emphasized midrange that's stronger than what happens below. With the Zero I this is part of the larger picture and akin to actual versus perceived temperature. Whilst an outdoor thermometer will show a certain winter reading, our personal sense of cold could easily exceed it by more than 10° due to wind chill factor or humidity.

In classic speakers an emphasized presence region is unambiguously wrong. Yet the Zero 1 opens this window to present sounds in it with full reverb and accompanying acoustics in a virtual instant. I thus rather think the midrange effect comes from uncommon speed rather than any actual amplitude emphasis. The midband appears stronger because we're used to a different presentation. The treble is quite sweet and detailed though it doesn't draw attention unless an instrument ventures into its range or a producer played with counter phase. Then it sparks into our vision. The bass is strong, low and fleshy. Especially for such a shallow enclosure its reach is amazing. The flip side is an upper bass that's not as saturated or chewy as it can be with classic speakers. Bass definition at the very bottom is superior but its tactile qualities are a bit more distant. Such is karma or perhaps these are the current limits of technology.

Conclusion. Reviewing these speakers was loads of fun. But that alone wouldn't be a fair wrap. The Zero 1 really puts everything in its proper place and perfectly scaled it to my room's size with panache. In Munich's 50m hall it played at higher SPLs and with greater forward projection than in my far smaller space at 2.5m from the listening chair. Yet I had no bass issues. Everything was simply slightly smaller than it'd been in Munich. In this ability to scale up or down the Zero 1 is phenomenal. It also has a special extra which returns music listening into an expectant mode of interest. That's important. However to cast the net wider still, the real strength of this design is how its form factor combines with ease of use which only then is supported by the performance. The outer shape is quite astonishing and to me suggestive of the monolith from Stanley Kubrik's 1968 masterpiece, 2001: A Space Odyssey. The curvature of the cast inset horns matches the rest of the shape perfectly. Connecting the Zero 1 to a source is a piece of cake. Anyone can do it, no in-depth knowledge of electronic gear required. Nor are there concerns over sudden software glitches or lost connections. Here this very complex very advanced systemic product resembled my ideal piece of audio kit: the legacy 'load it and hit play' CD player.

What would I change? Two things if I had HP's magic wand. I'd have the remote wand display volume level and selected source. Having no visual confirmation on how high the speaker was turned up was frustrating. I'd also fancy wireless transmission at higher than 16 bits. At present that's the only playback quality possible. But that's just me. Versus everything the Zero 1 Pro can do, that's only an old audio enthusiast grumbling. On the technical side the Zero 1 Pro is a complex system which nonetheless can be broken down into relatively simply bits which are then much easier to describe. We start with a 3-way fully active system of which the 25mm tweeter and 125mm midrange are horn-loaded for increased sensitivity and directivity. The horn mouths are 130mm and 400mm respectively. Their vertical configuration is inverted, hence the tweeter horn sits below the midrange horn. The 300mm paper-cone woofer with stiff impregnated fabric-pleat surround loads into a classic ported enclosure. It is covered with a grey fabric grill stretched across a stiff plastic frame. The speaker tilts back on an adjustable base and the tweeter should be aligned with your ears. But that's not the only possible adjustment. The rear baffle also sports a row of DIP switches to set the subwoofer output. My favored setting was +4dB.

The electronics mount to a large circuit board bolted to a solid and cast heat sink which resembles a car amp but is built better. Each speaker sports its own module but only the master unit accepts inputs. At our disposal here are two coaxial S/PDIF, Toslink, 16/48 USB and AES/EBU plus Ethernet. The latter is no Internet connection (which more and more firms embrace to build in software updates) but an alternate wired connection between the speakers. Since digital music signal enters only one of the boxes, the other syncs up wirelessly. That part can also be wired via Ethernet link. A careful look now reveals a set of analog XLR inputs. This option will go live soon to add an analog source. A suitable bay for the necessary A/D converter awaits inside already.

The modular electronics module combines Avantgarde's own building blocks with a Hypex UcD400 OEM woofer amp module with Dutch SMPS. The incoming digital signal hitting the main board runs into an AKM4113 digital receiver or the TAS1020 24/96 USB-to-S/PDIF transceiver followed by Avantgarde's custom-coded FPGA. CD-quality signal limitations are due to current design choices. The digital inputs use impedance-matching isolation transformers. After digital signal processing in the FPGA the signal proceeds to the 6-channel BB PCM4104 DAC module, then forwards to two amp modules on separate boards. The treble/mid drivers get classic class A transistor drive based on two mid-sized complementary transistor pairs per channel. Here top-quality high-power Dale resistors, Wima, Elna and Nichicon capacitors show how no money was spared. The class A modules share a custom SMPS with a far more complex circuit than that from Hypex. Due to the modular design construction one envisions easy future upgrades if and when applicable.

Technical specifications according to the manufacturer:
Subwoofer bandwidth: 30 – 250Hz
Midrange horn bandwidth: 250 – 2'000Hz
Tweeter horn bandwidth : 2'000 – 20'000 Hz
Horn sensitivity: > 104dB
Digital Processing: 6-channel 64-bit FPGA
Filter steepness: Up to 100dB/octave
Filter type: Progressive FIR filters
Phase shift: < 5°
Digital-analogue converters: 3 x 24-bit Burr & Brown
Power amplifiers: 2 x 50 watts + 1 x 400 watts
Master/slave radio link: 2.4GHz ISM/SRD
Amplitude linearization: Yes
Phase linearization: Yes
Room adjustment/equalization: Yes
Colors: White or black
Width x height x depth (cabinet): 490 x 1040 x 318 mm
Weight: 30kg
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