As you already know if you’ve read my review of the Avantgarde Acoustics Zero-1 Pro and Magico Ultimate 3 loudspeakers in Issues 245 and online, respectively, the horn-loaded loudspeaker is my little girl with a curl. When a horn speaker is good, there is nothing else that can beat it for dynamic speed and impact, low-level resolution, lifelike midrange presence, and sheer acoustical output. When it’s bad, well, horrid is not too strong a word for twelve-foot-wide instruments and voices, marked cupped-hands colorations, piercing treble, and audible discontinuity among drivers.
I’ve gone over the reasons for the horn’s strengths and weaknesses before in these pages, and I hate to put you through this same litany again. But on the off chance that some of you don’t hang on every word I write, I’ve prepared a condensed version to refresh your memories. (Readers who don’t want to suffer this ordeal again feel free to skip ahead about five paragraphs.)
On the plus side, first and foremost, is a horn’s ability to couple the sound it produces to the air of a room with far greater efficiency than any other kind of transducer. Like a megaphone (in fact, exactly like a megaphone), a horn constricts the area and volume of air that the driver attached to it works “into.” As a result of this constriction, the acoustic impedance of the air trapped in the horn’s throat—the narrowest part of the horn immediately in front of the driver—comes much closer to the high acoustic impedance of the driver’s featherweight diaphragm. This superior impedance matching allows that diaphragm to generate very high sound pressures from very small excursions. (Indeed, within its passband a horn-loaded driver’s diaphragm barely has to move, greatly reducing inertia and thereby increasing the speed with which it starts and stops, while also virtually eliminating its backwave—and the necessity of damping, venting, trapping, or otherwise coping with same.)
Moreover, as the horn’s tapered shape gradually increases in area toward its mouth—the widest part of the horn that opens onto the listening room—the high-pressure soundwaves generated in the horn’s throat by those miniscule vibrations grow lower in pressure and progressively larger in displacement as they travel down the horn’s length, allowing them to couple more efficiently to the low-impedance air of the listening room. In sum, a horn-loaded driver is in many ways the ideal acoustical-energy delivery system, typically producing ten times more acoustic output than a cone speaker would from the same amplifier power via an ultra-lightweight driver that, because of its greatly reduced inertia, is capable of astonishing speed and resolution.
Unfortunately, a horn’s negative side is also built into it. To wit, the very-high-pressure soundwaves generated in the horn’s throat can reflect off the throat walls. These reflections (and any high-Q resonances in the drivers themselves) will add a characteristic turbulence to the signal, which ends up being amplified along with the music. The sonic result is the “cupped hands” or “horn coloration” typically heard with P.A. systems. Additionally, though properly designed horns are inherently phase-correct transducers, the necessarily much wider disposition of their drivers (because of the physical size of the tubes they are attached to) can make overall time/phase/frequency coherence a dicey proposition.
Nowhere is this incoherence more pronounced than in the bass, which in many contemporary horn systems is often handled by a cone subwoofer. Seamlessly matching a cone sub to an ultra-fast, ultra-clean, ultra-high-sensitivity horn via conventional means is about as tough a task as you can set for yourself in high-end audio. Even the best direct-radiating cone subs will seem slightly sluggish off the line compared to the super-charged engine of the horn-loaded drivers.
When it comes to horns, I know whereof I speak, because about two decades ago I spent several years trying to live with an elaborate horn-loaded system—the original Avantgarde Acoustic Trio-G2—before finally, and not without serious misgivings, giving up on it. For all its strengths (and it had a lot of strengths, many of them unique), the Trio’s weaknesses—particularly its horn colorations, its incoherence (primarily in the bass but also, from time to time, among its trio of horn-loaded drivers), and its subsequent failure to disappear as a sound source—finally compelled me to moved on to other transducers, even though, with the right recordings in the right octaves at the right levels, I never again heard certain instruments and ensembles, such as grand piano and symphony orchestra, reproduced with quite the same lifelike scale, power, and realism.
Until recently I thought that a horn’s minuses were simply uncorrectable adjuncts to its plusses. Then along came the Avantgarde Zero-1 Pro and the Magico Ultimate 3, and all that changed.
Avantgarde’s and Magico’s use of digital signal processing to correct for the inevitable time, phase, and impulse anomalies of a horn/sub system simply erased the phasey imaging, cupped-hands colorations, piercing treble, and driver-to-driver discontinuity that had worn me down and out some twenty-odd years ago. Thanks to DSP, both speakers now offered a top-to-bottom neutrality and octave-to-octave coherence that I’d never before heard from a horn-loaded transducer. Both speakers now disappeared as sound sources almost to the extent that well-designed cones or planars do. When these newfound virtues were coupled to the horn’s unrivaled transient speed, resolution, and acoustical power, you got a speaker that in most ways competed with (and in some ways bettered) the very best dynamic and planars around.
I put “in most ways” in italics because of this: For me Avantgarde and Magico’s amazing fix of a horn loudspeaker’s perennial ills brought with it a new issue (“problem” is too strong a word), though I grant it is an issue that won’t bother others as much as it does me.