Apogee's most affordable speaker to date mixes moving coil bass with ribbon treble and midrange. The resulting hybrid has Alvin Gold angling for a good deal from his bank manager and Jonathan Kettle in awe of the speaker's effortless midrange detail.
After several years of reviewing and using Apogee loudspeakers, I am still not quite sure what their magic is. Essentially Apogee full-range ribbon transducers are very similar to other panel loudspeakers, which usually means electrostatics. Yet despite their manifold similarities, they do not sound the same.
Like electrostatics, Apogees are open backed because they sound awful when mounted in boxes (their diaphragm's large surface area and lack of rigidity mean that internal reflections pass right through). As a consequence they radiate in the distinctive figure-of-eight pattern that sets panels apart from most other loudspeaker types. Also like electrostatics, ribbons are driven evenly over their whole surface (correction, reasonably evenly over most of their surface), so there is no cone cavity to produce 'cupped hands' coloration.
Ribbons and electrostatics also share less fortunate habits. Their figure-of-eight radiation pattern throws as much sound backwards as forwards, and the extreme transparency of their diaphragms allows sound reflected from the rear wall to pass through, adding comb filter-type colorations to the forward output. Panel speakers don't interact much with side walls or ceilings but they sure need plenty of space behind, and even then tend to image 'in the lap' and in general behave in an extremely 'directional (read: 'antisocial') way. For all intents and purposes, Apogee speakers to date should be treated as enormous headphones, having a single, extremely localised sweet spot for listening. Move off-axis a few inches or stand up and snap - the illusion evaporates.
When everything is set up just-so, there really is a powerful illusion of performers in an acoustic. But gettings things set up just so usually means putting up with a murderously low and reactive amplifier load and low sensitivity. Persuading Apogees to - work right demands system building skills, of a high order and lots of lucre.
Potentially there is a way to get around at least some of these problems, as Apogee is now demonstrating with Centaurus, a range of three new loudspeakers from Apogee. Only the middle model, the Centaur, is available at present; the others - the Centaur Minor and Centaur Major (I'll leave you to work out the relationships) will become available over the next few months.
What is new about the Centaurus models are that they eliminate the large, costly bass ribbon and replace it with a conventional moving coil unit mounted in a conventional scaled enclosure. Coupled with this is a more or less traditional Apogee midrange/ treble ribbon driver. Voila!
The technology you can read about in the panel; the real point that needs to be made about the Centaur is that - in contrast to most such hybrids - it sounds so obviously 'right'. There is a facile quality to the Centaur: the music slips through, beautifully formed and utterly unexaggerated. At the end of a day's listening, I found it hard to say whether the Centaur was dynamic or squashed, what colorations it had, how well the bass was controlled, and so on and so forth. All such considerations were swept aside in an irresistible tide of fine music making. The Centaur didn't encourage analysis - rather, it encouraged me to wallow in the music, to lay back and think of my bank manager. It is surprisingly rare to find a loudspeaker with so much in the way of resolution, dynamics etc, yet which is so easy to listen to.
I am not suggesting that the Centaur was so incomparably wonderful as to be acoustically invisible. The Martin-Logan Sequels for one (it seems natural to bring this so similar yet so different dynamic/panel hybrid into the discussion) has a far more refined and exquisitely detailed upper midband, and provides the most extraordinary string tone I have ever heard outside a concert hall. The Centaur isn't quite that good, but what it does offer is equally persuasive: a consummate sense of rightness and of consistency. This is its great beauty.
Such qualities are not lightly won. The Centaur's composure demands comparable qualities of the rest of the system. It makes mincemeat out of small amplifiers once the volume is above a whisper and really only comes into its own with heavyweights in Krell and Audio Research territory, though electrically the Centaur is a comparatively easy, unreactive 5ohm load. I achieved fine results using Michaelson Audio Chronos valve amps and with a Krell KRL/KSA-100, though the most satisfactory combination I tried was the Krell preamp and Chronos power amp, which together extracted from the Centaur all those things you read about in the US hi-fi press - liquid highs, an airy, deep midband and a spacious, tuneful bass. The speaker proved surprisingly tolerant of positioning compared with previous Apogee designs, a benefit of the altered low frequency polar response.
I am trying hard to think of some real competition for the Centaur, but the more I think of individual models, the more the stature of the Centaur increases. There are speakers with a more solid bass (Snell) or more definition (Meridian etc) and some with a more refined mid/top (those Sequels again). But these don't really compete head on with the Centaur, or even fit in the same price category. The models that come closest to achieving a Centaur-style completeness and balance must be the better BBC-derived models - the big Spendors and Rogers, for example - though the Apogee bass is probably tidier (no side-by-side comparison was possible) and more three-dimensional in character.
Comparisons in this instance really are odious, however. If you have the room to house it and system to drive it, the Centaur is uniquely even in its capabilities.
Tucked away behind the panel housing
the Apogee's ribbon, there's a cabinet
for the moving coil bass unit
Hybrid two-way: dynamic bass and ribbon mid/top Bass enclosure scaled
Dipole ribbon fitted to outsize baffle
Stable construction - sealed enclosure reinforces baffle
Switchable bass and tweeter attenuators
Extremely fine Smooth, natural sound
Detail above average
Some people would walk to the ends of the earth to hear a pair of Apogee Diva loudspeakers. Full-range ribbons such as the Diva or the Stage have a reputation with a capital R. The hybrid ribbon/moving coil Centaur is Apogee's attempt to capitalise on that reputation at a price, which is by no means unaffordable by most audiophiles' understanding of the word.
The Centaur certainly looks the part. From front-on you'd guess it was a fullrange ribbon. In fact the panel in which the midrange/treble ribbon driver is mounted is bonded to the front of a cabinet that contains, in addition to the passive crossover network, a single moving coil bass driver.
This panel gives the Centaur its classic Apogee goods looks. Its veneered portion protrudes above the top and beyond the inner edge of each cabinet, creating an L-shape when the speaker is viewed from the side or from above. The remainder of the panel, which covers the whole front of the cabinet, is finished in black cloth.
Although the speaker is awkwardly proportioned it looks surprisingly elegant. Build quality is as good as you'd expect from Apogee; the cabinet is spiked at its base to provide good, stable coupling to the floor.
As I anticipated, the Centaur is not the easiest of speakers to drive. An Audio Innovations Series 1000/Second Audio valve monoblock pre/power combination ran out of steam on comparatively simple programme material, clipping the choral peaks of Poulenc's Figure Mumaine almost before The Sixteen under Harry Christopher's had time to take a second breath. A Krell pre/power combination might have done the trick. An Audiolab integrated amplifier did a passable job, though I'd hardly recommend such a combination. In the end I spent most of my time listening to the Apogees using a suitably affordable solid-state heavyweight pre/power amp from Conrad-Johnson Sonographe.
What I look for in a loudspeaker above all else is integrity, coherence, consistency and QED, believability. I can put up with coloration so long as it isn't gross or selective. I can put up with low sensitivity so long as the speaker delivers the goods with the help of a hefty power amp.
What the Centaur excels at is capturing the atmosphere of an acoustic and the subtleties of delicate instruments. I was in seventh heaven listening to albums like Jan Garbarek's I Took Up the Runes. The shimmering percussion, soaring sax and synth effects created a wash of ECM impressionism. The ebb and flow of that Poulenc, recorded at Snape Maltings, was also wonderfully evocative - sensual and haunting. The Apogee Centaurs captured the spacious acoustic very well.
Where they were less at home was with quicksilver, highly dynamic and hard hitting music. For instance, the very fast playing on Art Pepper's Straight Life left the Centaurs in its wake. The speakers captured the delicacy of the percussion and hung on to the sax as it twisted and turned, but the plucked bass was left floundering.
This track more than any highlighted the strengths and weaknesses of these speakers. Some listeners would die for that limpid, crystal clear quality of percussion; or for the way the ribbon transducer reveals the true nature of a bowed violin; or for the total openness on vocals and the sense of recording venue acoustic and atmosphere that this engenders.
My reaction is different. While I couldn't fail to admire these exceptional qualities I am left, perhaps as a result, frustrated that the the entire frequency spectrum is not afforded the same degree of clarity.
I tried adjusting the tonal balance but there was no way the quality of bass could be improved to bring its lucidity up to the level achieved in the midrange and treble.
Don't get the impression that there is some nasty discontinuity between the ribbon unit and the moving coil bass driver. There isn't. The loss of precision from treble to bass is gradual, and in most respects these speakers are wonderfully well integrated. There's a sumptuousness about the sound, a tonal sophistication and a complete absence of harshness, fierceness and aggression - although occasionally I could have done with more get up and go.
Although I have spent only about a week with the Centaurs, I feel I have their measure. I suspect that I may be able to wring an extra 10 or 15 per cent out of them with beefier, leaner amplifiers such as the Krells - an opportunity I would relish. If the Centaurs can be made to sound tighter and more integrated using a superior amplifier, I'd love to hear them again. But on the basis of my listening thus far, it would have to be one hell of an amplifier to put the extra fire in the belly of these speakers.
Why hybrid speakers make sense
There's nothing new about the hybrid idea, which has been taken up by Martin-Logan and others. Its key advantage is that it is a much more cost-effective way of building loudspeakers than is a full-range ribbon or electrostatic panel. To prove the point, the Centaur is the cheapest Apogee yet at £1895 a pair.
But there is a design problem with hybrids. Because moving coil units fitted in scaled enclosures have a different radiation pattern to open-back panel drivers, integration between bass and midrange is bound to be a problem.
Certainly it is a problem with the nearest equivalent to the Centaur that I know the Martin-Logan Sequel II. In its case the inherent qualities of the design are enough to overcome objections of poor integration, but the Centaur is different. It too is good enough to overcome objections, but such communications skills are hardly necessary. Remarkably, the seam between the moving coil bass and ribbon mid/treble drivers doesn't show in the first place.
At first sight, it is by no means obvious why this should be the case. The bass driver is built into a conventionally designed box on the front of which is fitted an outsize baffle which extends both inwards towards the centre of the pair (the enclosures are produced in mirror image pairs) and upwards. The ribbon is inserted into this extra 'land' and of course is unobstructed at the rear, resulting in a figure-of-eight polar response. The bass section radiates forward in a more nearly cardiod type radiation pattern. Instant incompatibility!
But the bass unit is positioned high, adjacent to the mid-point of the ribbon, which gets it well away from the floor. An important consequence of this is that the arrival time of the first (floor) reflection is later than normal for such a large loudspeaker, and comparable with compact loudspeakers used on tall stands since the bass driver is about a metre from the ground. This may help explain the fact that, although the Apogee's bass is on the full and warm side, it sustains a degree of clarity and agility that would do credit to a much smaller loudspeaker.
This design also brings the bass and midrange units into close physical proximity, aiding integration, while the sealed bass enclosure produces a satisfyingly well damped, unwaffly style of sound. It may also be significant that the bass driver bands over to the midrange ribbon at a very low frequency, and so is not responsible for much of the total output.
control is the one area where big speakers often lose out. In the Centaur's case
the high bass driver positioning makes it practical to use the unattenuated
(low) woofer switch option rather than the slightly drier (normal) setting.
There is little obvious loss of clarity with the greater bass output, but
voicing is so much more realistic. The tweeter can be switched in a similar way,
but the difference here is small and preferences are a matter of individual
taste rather than of special musical relevance. For the record, I preferred to
use the speaker with the treble unattenuated which seemed to me a marginally
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