MBL 101 X-treme Omnidirectional Loudspeaker 

 

That’s the theory, at least. And as I pointed out on the Gerry Mulligan/Ben Webster LP, with the 101 X-tremes the theory proves out beyond highest expectations. I personally have never before heard a baritone or tenor saxophone (or a piano or a bass fiddle or a drumkit or...you name it) reproduced with the same density of color, weight, solidity, and three-dimensionality—the sheer in-the-room-with-you presence—that the 101 X’s bring to the party. Those saxes (and other instruments) are just there, playing for you in your listening space. As I said ten years ago in my review of the original version of the X-tremes, “while we all listen, perforce, blind to stereo, the 101 X’s go farther towards compensating for our hunger to see what we hear—to fulfilling the definition of the word ‘stereo’ (which literally means ‘three-dimensional’ or ‘solid’)—than anything else I’ve auditioned.”

In addition to their incomparably full and realistic reproduction of tone color and 3-D presence, omnis have obvious sonic benefits when it comes to soundstaging and imaging—one of which you can demonstrate to yourself by merely abandoning the “sweet spot” midway between those cone loudspeakers currently ensconced in your lis- tening room. As you already know, when you move right or left of center, so does the soundstage, ​​​​​​which tends to collapse towards the speaker you’re nearing, as if the instruments and vocalists were gradually sliding off a tabletop tilted in the direction you're heading.

This does not happen in real life. If you move from centerstage to a seat at stage left or stage right in a concert hall (or a rock club, for that matter), the soundstage does not “collapse.” Oh, the instruments located in the direction you’ve moved sound louder and more prominent (because they are, in fact, louder due to your closer proximity to them), but the rest of the orchestra or band still spans the stage in the opposite direction, the soloist/vocalist still sounds roughly centered, the hall’s ambience still encompasses all instruments evenly, rather than thinning down in the distant direction and thickening up in the proximate one. With an omni, you get the very same effects you hear in real life. Sitting, standing, shifting your head or your seat, you experience the same stable imaging and soundstaging.

Omnis in general (and the 101 X’s par excellence) deal with room modes in an entirely different, rather more “generalized” and purely acoustic way—by flooding the entire listening space with full-range sound, coming (because the speakers radiate omnidi- rectionally both horizontally and vertically) from a nearly infinite number of different elevations and a nearly infinite number of different angles. You might think that en- ergy being broadcast in equal amounts at all frequencies toward literally every surface of your room would make the sound you end up hearing a confusing, echochamber-like mess. That it doesn’t has to do with two interrelated phenomena: a true omni’s (like the 101 X’s) frequency-independent, constant-directionality dispersion, and the Precedence Effect.

First, unlike conventional loudspeaker drivers (particularly tweeters) that tend to send intense spotlight-like beams of inherently more distorted off-axis sound toward sidewalls, an omni doesn’t “selectively” energize specific spots on your walls. As I noted, it doesn’t work like a specular flashlight. It works like a glowing ball. It energizes your room uniformly at all frequencies, so that any reflections will comprise the entire signal and not a small piece of it.

Of course, an omni is (by design) still creating far more broadband room reflections than a direct radiator, but we don’t hear them as echoes or distortions because of the Precedence Effect. The Precedence Effect is a psychoacoustic phenomenon whereby the acoustic signal arriving first at our ears suppresses our ability to distinguish any other signals, including echoes and reverberations, that arrive up to about 40ms after that initial signal (provided that the delayed signal is not 15dB or so louder than the first one). Instead of those late-arriving wavefronts being heard independently, they are “fused” by the brain with the first-arriving wavefronts and perceived as coming from the same spatial location. (These later-arriving broadband reflections also add volume level and spaciousness—particularly a sense of width—to the sound source, which helps account for the greater sense of presence, openness, and dimensionality that omnis, and the 101 X’s in particular, offer the listener.)

Far from being more colored by room reflections, drivers, and enclosures, sophisticated (and in the 101 X’s case, boxless) omnis can, in principle, be much less colored by all these things and much more faithful to sources (about which I will have more to say) because with proper setup they essentially take the room sound out of the equation. Thanks to the Precedence Effect and the fact that the speakers are lighting up reflective surfaces uniformly at all frequencies and all angles rather than selectively at specific frequencies and specific angles, your room no longer exists as a separate entity—like a picture frame within which the recorded soundstage is mounted (which is the way soundstaging generally works with a direct-radiating loudspeaker). Instead, the entire listening room merges with the recorded room, producing a wall-to-wall-to-floor-to-ceiling soundfield of astonishing layered depth, width, and height, and uniform ambience.

MBL Omnis and How They Work

Despite the brilliance of their design principle and the important things they got right, early omnis, such as the original Bose 901s and their many multifaceted descendants, were still essentially cones in a box—and liable to all the problems that cones and boxes entail. Notwithstanding the Walsh driver (an incredibly brilliant concept that suffered from a plethora of practical problems which initially limited its viability), it is puzzling that no one thought to make a pulsating spherical driver to imitate all those pulsating spheres in an orchestra or a band. And then along came MBL, which did that very thing, and then, a decade or so later, along came a world-class engineer named Jürgen Reis, who perfected MBL’s Radialstrahler concept and eventually designed the 101 X-treme that is the subject of this review.

In spite of all the genuine advances that have been made in the materials that cones and enclosures are made of (and, don’t get me wrong, those materials have greatly improved box-speaker sound), there isn’t anything fundamentally new about moving-coil loudspeakers (or about planars or ’stats or horns, for that matter). They are mature technologies, several of which have been around for almost a hundred years (more than that for horns). Yes, a carbon-fiber woofer is different (and sounds markedly different) than a paper or a plastic or a woven-fiber or a ceramic one. But it’s still a cone woofer with a surround and a spider, and it’s still sitting in a gigantic box (nowadays made of aluminum or carbon-fiber or some mystery-meat material called “X,” “Y,” or “Z”). A Radialstrahler, folks, isn’t like that. It’s not just another pretty face in the same old annual beauty pageant.

What is a Radialstrahler? It is a free-standing (unenclosed) spherical driver using a membrane made of bent segments that are fixed on one side and connected to a voice coil on the other. In MBL’s classic 101 E floorstander—the current version of the company’s original “radial loudspeaker” (which is what Radialstrahler means)—there are three spherical drivers mounted directly atop each other (and a conventional, ported subwoofer mounted beneath the radial array). The woofer (the large, bottommost radial driver) comprises 12 bent segments (called “lamella”) made of a proprietary alloy of magnesium and aluminum and arranged in a quasi-spherical (or melon-like) shape. The smaller midrange driver, which sits atop the cap piece of the woofer, also comprises 12 bent segments, made of a woven carbon-fiber material and arranged in a sphere. The even smaller tweeter perched atop the midrange’s cap piece has 24 bent segments, made of a proprietary unidirectional carbon material and also arranged in a spherical shape. When the drivers' moving coils move, the segments of the spherical drivers flex, creating sound pressure throughout 360 degrees, hori- zontally and vertically.

As all drivers share the same central axis, the listener gets, in designer Jürgen Reis’ words, the same “timing of the woofer, midrange, and tweeter...our alignment allows all frequencies to reach the listener’s ears at the same moment, just as they do in nature.

The 101 X-tremes

As was the case when I had the 101 X's ten years ago, setting up and dialing in the system was a two-day affair. The original installation involved many large and small adjustments in the physical location of the Radialstrahler towers and their woofer stacks; the second install went more smoothly, as Jürgen and Jeremy were familiar with the sound and layout of my room. Adjustments of the controls for each of the twelve Radialstrahler drivers and the two ambient tweeters on top of the Radialstrahler towers were done by ear, but tweaking of the gain, group delay (phase), and Q of the woofer stacks was augmented by measurements. (The crossover point between the woofer stacks and the Radialstrahlers is fixed at 105Hz with a 24dB/octave slope.)

Unlike the last time I had the X’s, Jürgen and Jeremy used (at my request) a DSP device ahead of the subs, between the MBL 6010 D preamp and the subwoofers’ built-in Class AB power amplifiers. As I said earlier, DSP’ing or analog EQ’ing subwoofers has been a positive in my experience—and it certainly was here.
Other differences from Jürgen’s first visit involved factory-installed improvements to the 101 X-tremes that MBL has made over the years: 1) the voice-coil formers of the tweeter and midrange are now constructed of a non-conductive material that eliminates eddy currents during the movement of the voice coil and, thus, any brakes on current flow; 2) the midrange support plate and support rods have been moved from the outer to the inner section to improve stabilization and shift any resonances out of the driver’s working range; 3) the cool-down process used in making the aircraft-grade aluminum segments of the radial woofer has been improved to reduce tension in the material and get a more fluid and “stressless” sound; 4) the group delay response of the woofer has been refined; and 5) composite materials are now used in construction of the struts and rods in the D’Appolito tower’s support system to further suppress resonances and improve stability.

After the boys left, I fiddled a wee bit with the controls on the subwoofers and with the level of the ambient tweeter atop the Radialstrahler stack to get the blend I preferred on the bottom and at the very top. Like everything else MBL makes, these controls worked with extraordinary precision, so no big changes were necessary—just a turn of a minute or so on the dials and I was ready to listen.

The Sound

As I wrote the first time around, “all of the various ways in which conventional transducers betray that their sound is being projected in narrower or broader dispersion patterns by individual drivers in resonant enclosures simply aren’t present.” What you hear, instead, as have been magically imported in toto from some other place—from a concert hall or a studio—and plopped down in your listening room with all three of its dimensions intact. To quote again from my first review, “where other transducers sound the way a film looks—like a two-dimensional medium imitating a three-dimensional reality— the 101 X-tremes sound the way a theatrical play looks—no ersatz third dimension, but actual people on an actual stage right there in front of you.”

Tonally, the 101 X’s are a bit bottom-up in balance—at least, they are when driven by the bottom-up-sounding MBL 6010 D preamp and two pairs of MBL’s 840W/40A 9008 A monoblock power amps. (I’m using two pairs of 9008’s, one pair per speaker side, because having two nominally 4-ohm 101 E’s in each Radialstrahler tower lowers their joint impedance to 2 ohms—a tough load for any amplifier. To be safe rather than sorry, I use one monoblock amp for each individual 101 E in the mirror-image pairs, and thereby sidestep the impedance-drop issue. I will be finding out how a single pair of monoblocks fares in the near future, when Vitus’ Signature Series SM-101 and Constellation’s top-flight Hercules II amplifiers are slated to come my way.)

Though timbre tends to be rich and darkish through the X's, it is not excessively so. From Diana Krall's playfully sultry contralto (on her wonderful cover of Joni Mitchell's great song "Amelia" from Joni 75) to Birgit Nilsson's steely Wagnerian soprano (on her icy and incomparable Elektra from the eponymous Strauss opera), from Hans Theessink’s Johnny-Cash-like bass-baritone on his terrific cover of “Sympathy for the Devil” (from Jedermann Remixed/The Soundtrack) to Richard Manuel’s scorched baritone on “The Shape I’m In” (from The Last Waltz—of course—though the versions on Stage Fright or Rock of Ages are just as memorable) to Neil Young’s sweet shaky tenor on “One Of These Days” (from the wonderful autumnal album Harvest Moon), vocalists never sound less than lifelike (having heard three of these singers in concert I can attest to this from experience). If anything, the touch of extra fullness, very similar to what you hear in a concert hall (and for the same reason), adds to the realism of vocals by enriching timbre and augmenting the solidity and dimensionality—the sense of rootedness in ambient space—that these speakers are very nearly incomparable at reproducing. (Instruments—from Fender bass to violin, from contrabass to piccolo, from kickdrum to ride cymbal, from tuba to tenor—benefit no less completely from this fullness of tone and 3-D rootedness.)

Possessed of the most seamless blend with main speakers I’ve heard, the sub stacks delve very very deep and do so with precisely the kind of richness you hear from bass-range instruments in real life—nothing is thin or razor-cut (all transient and no body); on the contrary, everything is warm, round, fast, cleanly defined in pitch, beautifully robust in timbre, perfectly timed in duration, and immensely powerful in intensity. (On the descending swirl of chords at the start of Bach’s famous Toccata and Fugue in D minor, which ends on a pedal of thunderous power, E. Power Biggs’ Flentrop organ plunges through the floor and shakes the room just like the real article.) You simply never hear these subs as separate sound sources, in spite of the fact that they comprise twelve 12" cones. As with the Radialstrahlers themselves, those push-push drivers are radiating their energy omnidirectionally—and radiating it at a multitude of heights and angles (thereby reducing the excitement of room modes, particularly when the subs are used in combination with DSP).

Dynamically, the 101 X’s are a wonder, as anyone who has heard them playing all-out at trade show can attest. (At very loud levels they can even make a jazz or rock drum kit, one of the largest and hardest-hitting of instruments, sound as “there” in the room as an oboe or a flute—a sonic feat I’ve only heard once be-fore with the Nearfield Acoustic Pipedreams, though the Pipes’ tar-barrel-sized subs were anything but seamlessly blended with their main columns.)

Part of the reason that MBL Radialstrahlers are so famously and enjoyably dynamic is the sheer amount of energy they are generating thanks to the unusually large surface area of their drivers. Consider a Radialstrahler woofer (the big silver melon-like driver at the bottoms and tops of the Radialstrahler towers). Every square inch of these large spheres is producing sound with the same intensity as the central portion of a conventional dynamic woofer (and without any of the center-to-edge drop-off in force or increase in distortion of a conventional woofer). In radiating area a Radialstrahler woofer is the equivalent of something like twelve 12" cones (the same number found in the sub towers). And each side of the 101 X-treme has two of them! The same thing is true of the Radialstrahler midrange and tweeter.

You might think that drivers this large in area would be slowed down by their mass and would ring like bells being struck when hit with an electrical signal, but their size actually works to their advantage. Since they’re driven over the entire surfaces, they only have to move very small amounts to make very loud sounds (a bit like horn-loaded compression drivers). These small excursions also mean that they don’t have to move very much to stop making sounds. Plus they are made of lightweight materials, and because of the volume of air inside them are virtually self-damping.

What do the X-tremes not do as well as (or far better than) the competition?

Well, they don’t image at center stage with the razor-cut precision of Magico M3s or M6s, though there is certainly an argument to be made for the somewhat larger, slightly more relaxed, far more three-dimensional imaging (and heart-stopping immediacy and presence) of solo vocalists or instrumentalists through the X’s. They aren’t quite as detailed as MartinLogan CLX’s, though they’re certainly no slouches when it comes to resolution (on a par with the very best dynamics), and it is well to remember that their detail is being folded into a three-dimensional image (and therefore not as nakedly exposed and separately audible as it is when details ride on the surface of a two-dimensional image, as they do with a ’stat or a planar or a cone). They don’t have quite the same slam or bottom-octave clarity of JL Audio Gothams—or they don’t at low-to-moderate volumes.

Turn things up, however, and it is a different story. For all their many virtues, other speakers just don’t do three-dimensional volume or lifelike size (without oversize) the way the 101 X-tremes do, so where the drum stroke on a tom or a bass drum may be very clear through a good cone speaker, the sense of the volume of air being excited in the drum’s circular shell isn’t as true-tolife as it is through the X’s. Inarguably, Radialstrahlers are not as extended on top as the best dome tweeters and ribbons. Indeed, the X’s’ radial tweeters roll off steeply and quickly above 16kHz (and are already a bit softer in intensity below that), which is one of the reasons for the ambience tweeter on top of each Radialstrahler array. Having said this, I must quickly add that MBL’s radial tweeters are still genuine marvels—the only HF transducers I’ve heard that do volumes as well as transients and colors. Through the X’s, cymbals have something you rarely if ever hear with domes and membranes—a disc-like roundedness that makes them sound three-dimensional, just as they do in life. (I should also point out that the 101 E’s roll in the treble means that they will not etch transients or artificially brighten up or add unpleasant edginess to harmonics.)

With their plethora of reflections and darker balance, you might well think that another of the X’s weaknesses would be transparency to sources, but you would be very wrong. Indeed, the 101 X’s are high among the most transparent-to-source loudspeakers I’ve had in my home. Why this is the case probably has to do with the absence of noisy, energy-storing enclosures, surrounds, and spiders, the radial drivers’ inherent time-and-phase coherence, their low distortion, their ability to stop and start on a dime, and possibly the sheer volume of sound they generate, but the fact is I haven’t had a speaker in my house that can tell me more clearly and quickly what is right or wrong about a recording or a piece of ancillary gear. (It was simply amazing, for example, to hear the way the 101 X’s sussed out the advantages of a very expensive cable vis-à-vis a cheaper, but still quite good one. Reviewing cables is always a chore, precisely because—outside of tonal balance and resolution—the differences among them take a while to gauge. Through the X’s it took all of two seconds to hear the way the new cables removed the subtle sibilance and midrange forwardness of the older ones.)

Conclusion

You already know what I think. These are the most realistic speakers I’ve heard, and though this has never before been the case, they are also the most musical and unconditionally enjoyable. Having eliminated almost all the things that make stereo systems sound like stereo systems, they are very nearly as unique in their non-stop sonic appeal as they are in their ingenious operating principle and brilliant engineering. Every time you listen to them is a pleasure and an amazement. And every time you stop listening to them, you want to come back. There is, quite literally, nothing else like them. Had I the money, I would buy them in a minute.