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Reviewer: Chip Stern
Source: Linn Unidisk 1.1 universal disc player; Upscale Audio Ah! Njoe Tjoeb 4000 vacuum tube CD player (in 24/192 Super Tjoeb configuration); California Audio Labs CL-20 DVD-CD Player; McCormack UDP1 Deluxe [on review], Rega Planar 25 turntable with Rega RB600 tone-arm and Grado Statement Master cartridge; Marantz PMD430 portable cassette player/recorder w. Audio-Technica AT822 one-point stereo mic and JPS Labs Superconductor FX mic cable
Preamp/Integrated: VTL 5.5 vacuum tube preamp; Rogue Audio Stealth phono preamp; Manley Massive Passive; Rogue Audio Magnum 99 vacuum tube preamp; Mesa Tigris; Linn Classik
Amps: Rogue Audio M150s [on review]
Speakers: Joseph Audio RM25si Signature Mk2 & RM7si Signature Mk2; Dynaudio Confidence C1 [on review]; Meadowlark Swallows; Epos ELS-3; Alon/Nola Li'l Rascals; Linn Tukan
Cables: Acoustic Zen Silver Reference II interconnects; Audioquest Panther interconnects and CV-6 speaker cables; Monster Cable Sigma Retro Gold interconnects and speaker cables; JPS Labs Superconductor 2 interconnects and speaker cable; JPS Labs Aluminata, Kaptovator, Digital and Analog AC, Superconductor 3 [on review]; Acoustic Zen Gargantua 2
Stands: Two PolyCrystal equipment racks, a PolyCrystal amp stand and PolyCrystal speaker stands
Power line conditioning: Equi=Tech Q650 and 2Q Balanced Power Systems; Monster Cable AVS 2000 automatic voltage stabilizer
Tweaks & Accessories: JPS Labs Kaptovator outlet center; Mondial Magic-Splitter; NEC CT-2070S monitor; Ringmat 330 and Signal Guard II isolation stand (turntable); Shakti Stones (electromagnetic stabilizers); PolyCrystal cones; Argent Room Lens; Echo Busters Bass Busters and absorptive and diffusive panels
Room size: 14' x 20' x 10', long-wall setup
Review Component Retail: $4,300/pr

No-nonsense affordable high-end loudspeakers for the rest of us

"Wow Chip, have you heard the new Tumescent Technologies floorstanding loudspeakers with a multi-driver array of Teflon-impregnated drivers sourced from Priapic Prestidigitators of Denmark, an eight-foot high molded Kevlar enclosure and an internal pair of 15-inch subwoofers in an Isobaric configuration outfitted with 50 pound magnets, cast titanium voice coils and a full four inches of computer-controlled excursion that can induce involuntary lower intestinal movements down to 3Hz, +/- 0.5dB? I mean, damn, talk about frequency extension, dude. Those speakers go down like a Las Vegas hooker."

Very impressive indeed. I must confess though that I'd be far more impressed if my listening room was configured along the lines of the Sistine Chapel and I had a half a million dollars to spare.

If money (and weight) are no object and you can build the enclosure (enclosures?) as large as you'd like, why shouldn't an audio designer be able to make a full-
frequency speaker capable of wringing every last ounce of bass extension from the Saint-Saens Organ Symphony?

However, for those of us residing on Planet Earth, our budgets and acoustic spaces dictate a different sense of priorities, analogous in some ways to the old saw about how the girls that you go out with are not the girl you ultimately marry. Which should in no way preclude our enjoyment of something as awe-inspiring as the Wilson Audio X-2 Alexandria nor take away an iota of credit from their designer and his team for their breathtaking achievement in a no-compromise speaker design. However, unless you enjoy an intimate relationship with the proprietor of Rumpelstiltzkin Audio and the old man is willing to accept your first-born child in trade... well, c'est la vie.

So while our ongoing fascination with state of the art systems proceeds unabated, the real challenge in loudspeaker design remains, as always, to create a high-performance/high value product that delivers an authentic immersion experience. That is to say, it delivers the spirit and reality of live music, true musical timbres and a convincing sense of dynamics within an identifiable acoustic space. At something resembling an affordable price. In a sensibly apportioned cabinet that maximizes the performance of the system's transducers without frightening your wife and kids.

Such is the acoustical and aesthetic splendor of Acoustic Zen audio designer Robert Lee's finest achievement - a loudspeaker design for the rest of us. His Acoustic Zen Adagios, by any measuring stick you care to reference, rank among the finest price/performance offerings in contemporary high end audio. Period.

Bold words to be sure. But not without serious substantiation as we shall see. Already well before I first heard the Adagios, reports filtered back to me of people walking out of auditions as if they'd seen the burning bush and heard his master's voice. I count among these several people I know and whose ears I trust, as well as total strangers who just happened upon the Acoustic Zen suite at the 2006 Las Vegas CES Show. Independent of any formal affirmation by un critico più importante (repeat after me: in nomine de bassopatri, de phillemidrangi, y treblejurno de criticus sancti) and based simply upon enthusiastic word of mouth, they and others managed to delay my own encounter with these loudspeakers by several months until the mid-summer of 2006. Dealers and consumers had been buying out Acoustic Zen's entire initial run of Adagios [and subsequent ones it seems; more than 400 pairs have already been sold - Ed.]. As I endeavored to put this review to bed, several readers wrote me who'd already purchased a pair of Adagios and simply wanted my benediction. Or who, while ready, willing and able to make a purchase, awaited my personal Amen and aural encyclical. Bless you, my children. Cough.

Now that's enthusiasm. So enthusiastic in fact that it put me in mind of that bawdy encounter between Sheriff Bart and the Teutonic temptress Lili Von Shtupp, in Mel Brooks' Blazing Saddles.

[Lili Von Shtupp has lured Bart back to her room]
Lili Von Shtupp: Is it true how zey say zat you people are...gifted?

[Lights go out, sound of zipper opening.]
Lili Von Shtupp: Oh. It's twue. It's twue!

Cough. Yes, the buzz preceding the arrival of my Adagio audition samples was truly impressive. Still, this word of mouth did not completely take me by surprise. Some years back I was visiting my daughter in San Diego. I dropped in on Robert Lee at Acoustic Zen where I auditioned a number of his cables. Subsequently in his home, I heard some of his other audio designs, including a smooth, dynamic sounding, pure Class A 100pwc Mosfet-based power amp and a pair of small, elegant, stand-mounted loudspeakers which -- as I recall -- featured a horizontally mounted 5-incher with adjacent bass reflex port. The loudspeakers were very musical and sounded enormous yet my interests in obtaining audition samples were rebuffed. They did not represent a final production model. Robert felt he could take this basic design much farther.

Given this background, I nevertheless wasn't quite prepared for the actual experience of the Zen Adagios, either straight out of the box, after a month-long burn-in or during the home stretch of this review as I awaited the arrival of a true high-powered amp. The Adagios make you step back to contemplate anew what principles are really important and enduring in speaker design even as they signify a breakthrough in basic high-end audio performance values. Having now listened to the Adagios for a few months with some high-quality if modestly endowed amps, I am finally ready to weigh in with my conclusive impressions.

I Enthuse, Therefore I Am
I am painfully aware that such unbridled enthusiasm as my Overture alludes to raises the neck hairs of some audiophiles who have been burned time and time again by the bend-over-Beethoven bombast that may pass for reviews on some websites. Been there, done that. I can readily understand how such cynicism derives.

Many of us are unduly impressed by the gear itself, let alone by price points well beyond our reach. Somewhere along the line, the received wisdom amongst audiophiles is that the more expensive the gear, the more soul went into it, hence a surer proof of our own elevated sensibilities, i.e. incontrovertibly better. Such bold pronouncements are bound to turn off the uninitiated or elicit a standard beg-off: "I could never hear the difference." Which roughly transposed from English into TruSpeak means "I'm deathly afraid that I would hear a difference and thus might be compelled to pay for it (and send my wife screaming into litigation)."

Anyway, having acknowledged that this review is a rave, is likely to proceed as a rave and most probably will end as one, let me cut to the chase. Having put the Adagios through their paces, I found very little to grouse about. In fact, when I find myself referencing speakers I like just as much or maybe even more, they are invariably more expensive and more specialized, such as the diminutive yet musically awe-inspiring Dynaudio Confidence C1 mini monitors or the latest iteration of the Vandersteen 5A, a thoughtfully conceived, brilliantly executed full-frequency floorstander with an integral subwoofer (and its kid sister, the Vandersteen Quattro). Those are both simply superb in their honest musical presentation of real-world dynamics, the natural tonalities of actual acoustic and electric instruments and a palpable sense of an authentic acoustic event.

Now it's worth pointing out that the small bookshelf-sized, mastering-quality two-way C1s (when festooned to their integral stands) come in at around $6500/pr while the large, multi-driver 5As (with special external crossovers for their tunable subwoofer section) rock the boat at around $15,400. So am I saying that the Acoustic Zen Adagios are better speakers? No - but with system synergy and relativity ... everything's relative.

When I am listening to the Zen Adagios in my reference system, I smile contently. In terms of their lack of audible distortions or colorations, sheer coherence and resolution, absolute clarity and timbral detail, dynamics, rhythm and pacing, frequency extension, spatial veracity and ambient cues, the Adagios hold their own with some of the best speakers I've ever heard. This includes my longtime reference standard, the comparably priced Joseph Audio RM25si Signature MKII.

Let's put it this way. The Acoustic Zen Adagios deliver extraordinary proportions of the audio verity one has come to expect from the best small and large loudspeakers - and not just at their relatively modest price point. In many cases, they stack up proudly against speakers selling for two to three times their price.

Are there better speakers? At generally higher price points, surely - and at much higher ones. However, at around $6000 or under, the Adagios can hold their own with anything. And to these ears, in terms of certain heretofore overlooked performance values, they in fact represent something of a new standard.

Interview with Robert Lee
Between the two drivers, is one handling low frequencies and the other both midrange and bass as in a 2.5 way design?

No. It is a true D'Appolito-style array. Both 6.5" drivers are wired in parallel and handle 30Hz to 3000Hz. This style design employs two low-frequency drivers with a tweeter in the center. Such a configuration creates a larger sweet spot. It gives you greater low-frequency extension along with two-way coherence.

Tell me about your woofers. How does an underhung driver differ from a well-hung driver?

Underhung means that it has a very short voice coil in a large magnetic field gap. The drivers are top grade and so are the magnets. The voice coils are very narrow and always move in a linear manner within a magnetic field regardless of excursion. Additionally, a traditional long voice coil moving in a short magnetic gap presents a high variable impedance to the amplifier.

Can you break it down in some more detail?

With a short voice coil in a long magnetic gap, as the music signal flows through the voice coil, the coil and the cone moving together produce the sound wave. A long magnetic gap structure offers a much wider linear magnetic flux density, alternately pushing and pulling the short voice coil back and forth. Since the magnetic force on the coil is constant and completely symmetrical with the motion of the piston assembly, the result is a sound wave with extremely low distortion and coloration, allowing it to respond much faster to a transient signal and to stop faster after the drive signal has ceased.

Compare that with the large signal behavior of high-excursion overhung transducers. Because the coil extends beyond the control of the magnetic flux field, it causes very high harmonic and transient distortion that can reach 5 - 20% whereas the underhung driver maxes out at 1%. Because of the very complex magnetic structure and complications involved in voice coil placement and fabrication, the underhung voice coil is difficult and expensive to fabricate.

What are the speaker cones made of?

They use a ceramic-impregnated fabric in the center with ceramic coating on either side to form a sandwich. These drivers are custom built for Acoustic Zen to my specifications. The ceramic coating makes for a strong, dense, rigid surface area that will not break up nor produce a lot of ringing. The cone is very stiff and light and as a result, very fast. It responds immediately to a signal and returns to its original position very quickly. This minimizes frequency overhang, colorations and distortions.

Why a Neodymium magnet?

An underhung driver's voice coil requires an extremely strong magnetic field. If you are using traditional magnets, the size and weight of the motor would be excessive. Neodymium allows us to maximize magnetic coverage while controlling weight and size.

Why did you choose a ribbon tweeter and how does your circular design differ from other approaches?

I don't want to get too technical here. My circular ribbon tweeter design, unlike a traditional dome or cone tweeter, presents a purely resistive impedance that's completely linear in the audio range. It also has an essentially linear phase response, which contributes to an immediate and precise response to any transients in a complicated music signal. This dramatically reduces distortion and coloration.

I am using the thinnest diaphragm possible, a 0.01 millimeter Kapton diaphragm. That's just about weightless, with a 95% covered aluminum circle of conductors across the entire vibrating area positioned between super strong Neodymium magnets. Some people use metal ribbons which can result in very harsh HF response. Kapton is not only extremely light, it is also heat resistant, hence the thermal behavior of the voice coil will not translate into audible distortions. My tweeter's larger circular membrane not only provides much higher power handling and a wider frequency response, it also eliminates the offsets between horizontal and vertical dispersion that are common with narrow ribbons.

What kind of crossover are you using?

We employ a symmetrical 18dB/octave 3rd-order high and low pass.

Some people believe that a simpler crossover gives greater sonic purity - that the more complex the crossover, the less natural the sound.

A 1st-order network would have been impossible in this system because of the overlap of frequencies. You have to use a very complicated audio circuit to filter down the frequencies that will cause issues with both impedance curves and distortion. Because our crossover point at 3000Hz is fairly high, we don't want the tweeter to handle midrange frequencies or vice versa. We want the woofers to cut off almost immediately. Because of the kind of speed and accuracy we wanted to achieve in the low frequencies, a 6.5" driver offered the best balance of linearity, frequency extension and speed. Larger drivers would cause other problems when paired with a 1.5" circular ribbon tweeter.

What was your thinking in terms of the shape of the cabinet where it gradually narrows toward the back?

The shape of the cabinet and the reduced size of the acoustic chamber/line subtract by almost 90% the back waves, standing waves and other distortions reflecting back to the drivers. The shape of the cabinet and the time-aligned vertical driver array reduce driver diffractions while providing a good acoustic center which improves soundstaging.

The sides of the cabinet are 1" MDF while the mid/woofer front baffles add up to a total of nearly 2" depth. Between the baffle and the cabinet face, there is an additional layer of decoupling damping material to absorb driver motion.

Not well but low hung
[Bart returns unexpectedly after being sentenced to death]

Charlie: They said you was hung.
Bart: And they was right.

Blazing Saddles]

Right out of the box, the Acoustic Zens' fit'n'finish is pretty damn impressive. Available in a choice of wood veneers, the standard Adagio comes with a sumptuous, wine-red translucent finish that allows the grain of the wood to peek through. My sample came in a richly faceted burl maple veneer that encompassed the entire cabinet from front to back, polished to jewel-like perfection with a glistening clear coat that adds great depth and detail to the wood grain. It reminded me of some pearly white opals I've seen with speckled flashes of color. Everyone who saw the cabinet freaked over the finish and seemed compelled to touch it. This reverence reminded me of when I first encountered the Sonus Faber Amati Homage in an earlier iteration of Rabbi Michael Fremer's aural tabernacle. With their tapered cabinet shape, lute-style stave construction and superb finish, they reminded me of an Egyptian sarcophagus - more like marble than wood. As alluring as the gently tapered curves and contours of the Adagio's cabinetry are, gradually narrowing from front to back, they exist not merely for aesthetic effect but are designed to reduce cabinet diffractions. A flared front-mounted port on the bottom is the termination of the transmission line.

Robert Lee's robust internal wiring (his proprietary 10-gauge zero-crystal copper Satori), solid cabinet construction, time-aligned D'Appolito configuration, transmission line loading and system tuning all reflect his desire to provide the flattest, most stable phase and impedance curves, the easiest possible load for an amplifier and the deepest, tightest, most tuneful bass. To accomplish these goals, the most important of Robert's design considerations was to reduce driver distortions.

To that end, Lee built and designed his own 1.5" circular ribbon tweeter and sourced out his concept for a pair of 6.5" bass drivers featuring ceramic-impregnated fabric cones designed to cross to the tweeter at 3000Hz. I can attest to the remarkable clarity, detail and coherence these drivers convey because I was able to consistently drive the Adagios to volume levels which in the past might have induced considerable glare and fatigue. These drivers are very fast, very nimble and very extended without being bloomy or boomy, edgy or bright. They produce honest bass, a lovely layered midrange and smooth, natural highs that do not impart any sonic glare or unnatural sheen. At the risk of repeating ourselves (much of this is also covered in the sidebar interview), to Mr. Lee the most significant aspect of his Adagios is their use of both a ribbon tweeter and underhung drivers in such a relatively cost-effective high-end design.