A+Audio Voxativ Revisited

Jan 31, 2014
Extra: Kari Nevalainen

I don't easily fall into mysticism. That is, I don't think truth is absolutely indefinable. This time, however, I had an irresistible desire to ignore definitions and technicalities, and indulge in the stream of immediate impressions, to let my reason be overridden by my ear & heart, and just go for describing the sound as I felt it.

The fact is that the single-driver loudspeakers by the Finnish A+Audio built around Voxativ widebandwidth drivers are able to do some pretty magical things. For one thing, they are capable of extraordinary musical coherence. But on top of that - after all, coherence is a virtue of other widebanders too - these speakers amaze the listener with their stupefying sonic transparency and clarity, with a myriad of sonic facts that the listener didn't know that they existed, or had not paid attention to them earlier. Add to that their excellent transient response, especially on a micro scale, and the way in which music flows and glides naturally from a sequence to another, from a note to another.

All other things being equal, only a very few loudspeakers can captivate the attention of the listener as these speakers do. They impel the listener to concentrate fixedly on the music in anticipation of the musician’s next move, further strengthening the emotional bondage between the listener and the music that is being reproduced. I’ve seen people applauding as a spontaneous reaction to what they’ve heard and experienced with these speakers.

It would be a miracle if such a level of musical involvement could be achieved by means of mystical experiences. It is not. In single-driver loudspeakers, a great deal of the “magic” will be explained by the driver itself: once the signal reaches the voice coil, with no filtering whatsoever, it's too late to fix the course if it wasn’t right in the first place. It either succeeds or it sucks, much depending on the quality of the driver.

Voxativ is a relatively young German company, but the drivers it makes have a long history dating back to the first half of the 20th century when the UK based Lowther first begun to manufacture fairly similar 7 inch, high sensitive widebandwidth drivers with a powerful magnet and a light paper cone. Later the driver was supplemented with a whizzer cone for extended high frequency response.

Although 7-8 inches is very much an ideal diameter for a widebandwidth driver (ie. there's enough surface area for producing reasonable bass without compromising too much in the treble), it's anything but simple to manufacture a driver that would cover the entire bandwidth with an equal efficiency.

To have a decent bass without too much distortion, Voxativ drivers feature a convex surround made of special foam to accommodate an excursion of 8-10mm, which is clearly more than that of traditional Lowther drivers. To offset frequency response irregularities and phase shift, and to ensure an adequate and smooth treble response, Voxativ has reworked the cone geometry, including the profile of the outer edge of the whizzer cone.

As to magnets, ever so critical to the performance of widebandwidth drivers, Voxativ has chosen a liberal policy: it offers ferrite for less money, alnico for connoisseurs, neodymium for small size, greater power and longevity, and finally, field coil for those who want and can afford the ultimate.

With their relatively low Q-factor (Ots typically 0,3), and the resonance frequency in the 40-60Hz range, Voxativs, like Lowthers, are designed, by default, for rear horn loading, meaning that the lower frequencies of the driver's backward radiation get “amplified” (ie. better coupled with air) through a pressurized chamber behind the driver, and a horn, straight or folded, of a certain shape and length.

A+Audio’s Acoustique resembles the classic Lowther Acousta but is both narrower and taller than it. The horn is shorter and more sketchily cut than the one in Voxativ’s own Ampeggio speaker but the main profile is the same.

Only 30cm deep Floorhorn sports a straight (not folded) horn shooting directly down the floor, and leaving 6,5cm between the horn mouth and the floor.

The most compact of the three A+Audio speakers is a ported model called Bass-Reflex. As with other models, all dimensions and tuning specifications are worked out under supervision of Voxativ's experts.

And the drivers? It depends. The cabinets do have their favourite Voxativ drivers but are not strictly designed to carry any particular one. I’ve heard each model equipped with at least two different Voxativ drivers with different sonic results.

Having said that, I think it would be natural to see the Bass-Reflex go with the least expensive Voxativ AC-1.5 (now AC-1.6) with a ferrite magnet. The AC-3x, the very same driver that Voxativ employs in its Ampeggio loudspeaker, would be a natural companion to the Acoustique, and finally, for the Floorhorn I’d choose either the AC-3x or the flagship AC-Xp.

In the SweetSpot 2013 in Stockholm in October, the Floorhorn housed the AC-3x, which is pretty optimal for that cabinet.

Independently of the driver model, the sonic strength of the three A+Audio speakers (and Voxativ’s own models, for that matter) is their relatively smooth performance from roughly 400Hz up to 8-10kHz. The infamous upper “midrange shout” of at least some Lowther models and their drivatives, is gone out of the window, if not entirely, then at least largely speaking and even at higher volume levels. That's a good news since those five octaves are where most music lies, and it’s with music that these speakers shine.

Exactly how much high-frequency (5kHz to 15kHz) energy is present for the ear, ie. how bright or crisp the speakers sound, depends, among other things, on the speaker/ear angle: on axis the speakers sound at their brightest, and for the flattest response the speakers need to be directed 18 degrees away from the ear.

On the other hand, it is characteristic to these speakers that they tend to sound bright and midrangy. Some listeners may be allergic to that kind of brightness, but that’s not the speaker’s fault. "Bright" in the context of A+Audio’s Voxativ speakers does not imply “too bright” or "hostile to music". It implies “overt and revelatory”. It implies “no filter”, it implies “tangible”, it implies “life”.

I recently compared three widebandwidth speakers, one of which was A+Audio’s Bass-Reflex. The Bass-Reflex was by far the “brightest” of the trio, but it was also by far the most rewarding and happiest to listen to, despite some frequency response oddities, and even with such hard to reproduce music as piano recitals.

It should never be forgotten that "brightness" is always a function of the overall tonal balance. For single-driver loudspeakers, the overall tonal balance is everything. Once the sound is tonally balanced, and the lower end and the higher end sing in harmony with each other, music comes out perfectly satisfactorily even if the speaker can make a narrower bandwidth (say, frequencies from 60 to 10000Hz), and even if there are some irregularities in the response.

The Achille’s heel of any widebandwidth speaker is the bass below the frequency at which the driver will short-circuit the bass unless prevented with a cabinet. To find a proper loading by means of a suitable cabinet is perhaps the toughest tasks in designing a high quality widebander. There’s either too little bass or too much of it, or the bass is phasy and not extended enough. And what have you.

No wonder, then, that all A+Audio's speaker models sound different in bass, and in terms of their tonal balance too. The Bass Reflex has usable and quite well integrated bass down to midbass, but can sound a tad lean and pale over the lower midrange. This is not a speaker for friends of Metallica.

The Acoustique is able to produce an ample amount of mid to upper bass providing good support to music that benefits from it. On the other hand, what comes out of the horn mouth can interfere with the direct sound of the driver, and the room, in a way that must be taken into account in positioning the speakers for the best balance.

The Floorhorn has a good bass without sounding bassy. There is less interaction between the rear bass and the direct sound, and the bass is not as sensitive to room resonances as in the Acoustique. But like with the Bass-Reflex the area from upper bass to lower midrange may appear under-represented, unless taken care of.

One way to adjust the bass is to move the speakers closer to each other, or further away from each other depending on the room characteristics. I've heard the Floorhoer and the Acoustique in large rooms, and there the speakers placed wide apart has worked great, other rooms favor a narrower listening angle.

There’s less variation in treble performance between the three models. The more expensive Voxativ drivers appear to bring in certain refinement and sophistication over the upper register, but the differences aren't qualitative, just of degree. All drivers, and hence all A+Audio speaker models, exhibit the same characteristic HF Voxativ sound.

There is a reverse tendency too: the more refined the treble gets the thinner it gets, or so it feels. This is perhaps a welcomed feature for string quartet aficionados, but those who possess a more earthly taste of music may prefer a slightly thicker presentation.

Let's consider a couple of propositions that I think are pivotal for understanding these speakers.  First, from music’s standpoint there's practically always too much bass. I'm not against of pursuing the low bass but it's true that reproduced music does not demand the presence of the bottom octave in order to be fully enjoyable, only sound-lovers think otherwise. So forget the boring, musically irrelevant questions of whether the speaker can produce the open B string (31Hz) of a five string bass guitar or the 16Hz organ pedal. People understood this already during the first half of the 20th century, and the same applies to the relevance of the top octave (>10kHz), although there the questions are slightly different.

Secondly, the bass produced by a rear horn is qualitatively different from that of a forward shooting woofer. I don't mean that individual bass notes would come out differently but that the quality of their quality is of different kind. This characteristic is not easy to grasp before one gets a chance to listen to a rear horn speaker in a more profound way.

Third, these speakers more than many other speakers exemplify the “carbage in, carbage out” principle. This concerns the choice of the accompanying amp and cables, but in particular the  software: the recordings. Many people seem to think that single driver loudspeakers are fit only for a certain kind of music (acoustic guitar, female vocal, chamber etc.), but not for all music equally. But that’s a misbelief. Take some well-recorded LP from the 70s containing rock or rhythm& blues, and it’s bound to come out fantastically with the Floorhorn, for example. Take one superbly recorded classic or jazz LP from the 50s and 60s, and again, the experience can be breath-taking. Choose a modern recording that is mixed & mastered to sound flashy on commercial radio, the 30 first seconds will make one sick.

Finally, these are not speakers for sound lovers. What really distinguishes those who align themselves with single-driver speakers from the rest of the audiophile gang, is not what music they prefer to listen to but their general attitude toward music. People who first react to whatever it is that makes a particular music worth experiencing, independently of which music it is and how it sounds, are likely to like these speakers. People whose main worry is how a certain music sounds, probably hesitate, not because the sound of the speakers would be somehow inferior, but because they miss their point completely.

Like all single-driver speakers, A+Audio Voxativ’s aren’t easy to tame. But when everything's right, they will bestow unforgettable musical moments.


Last updated
Tekninen toteutus: Sitebuilders Finland Oy