About two years ago, I got a call from THX’s PR representatives asking if I’d like to take part in a briefing on the world’s first THX Ultra2-certified in-wall subwoofer system. Core technologies for the system, I was told, were being developed by THX chief scientist Laurie Fincham (perhaps best known for his achievements as the former Technical Director for the British speaker-maker KEF), while the resulting subwoofer system would be manufactured by BG Radia, of Carson City, NV. I was eager to learn what Fincham and BG Radia would do when given the freedom to create a world-class sub, so I signed up for the briefing and was soon introduced to a radical new woofer system design that breaks all the established rules, and for all the right reasons.

Let’s play a word association game. If I say “state-of-the-art subwoofer,” what thoughts first come to your mind? My bet is that you are picturing a big, honkin’ precision-made woofer (or two) loaded into a beefy, bank-vault-like enclosure and that is powered by a take-no-prisoners amplifier with enough output to propel a hybrid car. Well, apart from the amplifier part of the equation, let me tell you that the BGX-4850 subwoofer system ($6995) is nothing like that.

Flying in the face of tradition, Fincham and the BG Radia team have developed a multi-component woofer system comprised of four extremely compact yet very high output in-wall woofer modules that are—get this—inherently vibration canceling, plus an outboard controller/amp module to power them. Interestingly, Fincham never saw the in-wall aspect of the system as a performance-limiting factor. On the contrary, he felt the size constraints of an in-wall sub compelled him to think—quite literally—“outside the box” to create new woofer technologies that offer a fundamentally better-sounding way of reproducing bass frequencies. To appreciate the true character of this BG Radia woofer system, then, don’t think of it as an in-wall product, per se, but rather as a world-class sub that also just happens to support in-wall mounting.

Specifically, the BGX-4850 subwoofer system is meant to address five specific design goals:

Provide THX Ultra2-certified output capabilities.
Achieve well-distributed and extremely evenly balanced bass response throughout the listening room.
Deliver excellent low-frequency extension with exceptionally fast transient response, great pitch definition, and terrific timbral purity.
Achieve all of the above in a compact and virtually invisible in-wall format.
Achieve all of the above in a design that cancels out woofer cabinet vibrations, thus minimizing problems with resonance and vibrations in wall studs and/or sheetrock panels (problems that can crop up with high-output subs of any kind).

As the THX/BG Radia press briefing came to a close back in 2007 I expected that a production-release version of the BGX-4850 system would appear within a few months, but it was not to be. When manufacturers are chasing state-of-the-art performance it can take longer than you’d think to get those final few product details just right, which was certainly the case with BG Radia’s new super woofer. Trade shows came and went yet the final production version of the BGX-4850 system remained tantalizingly beyond reach—until just recently. But as you’ll see in a moment, it was worth the wait.

OVERVIEW

Consider this subwoofer system if: you judge subs by their sound, not by their looks. (BG’s system looks fine, but—in in-wall form—is essentially invisible). This system performs exactly as advertised; it provides high output, deep bass extension, lightning fast transient response, great pitch definition and timbral purity, and evenly balanced bass output all over the room. Unorthodox though it may be, this is one of the two or three best subs I’ve heard at any price.

Look further if: you want massive “trophy subs” to show off to your buddies (the BGX system duplicates the output of two conventional 18-inchers, but is low on “bling factor”). Look further, too, if you are cost conscious or require an in-room solution (BG’s in-room enclosures won’t be available ‘til later this year). The only serious omission is lack of a built-in room/sub EQ system—a touch we would certainly expect in a woofer system in this price/performance class.

FEATURES

The BGX-4850 subwoofer system consists of five main components: four SM-1250 in-wall woofer modules (with grilles), and a standalone, rack mountable, remote controlled BGA-2104 subwoofer amplifier.
THX Ultra2 certification guarantees low frequency extension down to 25 Hz (or better) at -3dB, and assurance that the sub is capable of THX Reference Level output in rooms up to 3000 cubic feet.
Billed as “the world’s first THX Ultra2 in-wall subwoofer,” the BGX-4850 system’s compact woofer modules comfortably fit within the stud spaces of interior walls framed with 2” x 4” studs. Alternatively, the woofer modules could be mounted in a ceiling, or even slipped under couches or shallow cabinets.
BG’s SM-1250 woofer enclosures use proprietary THX Balanced Bass-line technology to cancel out woofer cabinet vibrations. Fincham’s ingenious, “boxer-style” enclosure features two sets of six drivers that are horizontally opposed and arranged so that their diaphragms pump inward and then outward in unison, so that vibration forces exactly cancel out. Sound is output through a forward facing slot that measures roughly 2” x 22.5”. Even when the woofers are playing loud and low, the enclosures housings exhibit virtually no discernible vibration.
BG’s multi-woofer module format allows modules to be positioned within as many as four wall surfaces for exceptionally even and well-balanced in-room bass response. (Example: in the Playback lab the system delivers bass response of 18Hz to well over 100Hz, ± 2-3dB, across multiple listening locations at once).
The BG Radia system uses a total of 48 small-diameter 4-inch drivers (12 in each woofer module) that are light, fast, and responsive—yet that offer bass extension below 20 Hz. The upshot is a subwoofer that is powerful and goes deep, yet that sounds audibly “faster,” more nuanced, and more transparent than most. Interestingly, BG’s 48 small drivers have the combined radiating area of two conventional 18-inch woofers, so high output is never a problem.
BG Radia offers separate in-wall mounting kits for both new construction applications and retrofit applications. Recognizing, however, that some customers will require an in-room solution, BG Radia has teamed with acclaimed industrial designer Allen Boothroyd (co-founder of Meridian Audio, Ltd.) to develop a combo on-wall/in-room enclosure for the SM-1250 woofer modules. The in-room enclosures are slated for release later this year.
The electronic “heart” of the system is BG Radia’s BGA-2104 Subwoofer amplifier with provides 2200 watts of power, extensive control functions including DSP and a remote control.

How can this be? The answer involves two important BG Radia design decisions. First, by using many small bass drivers (48 x 4-inch units) rather than a few much larger and more massive woofers, BG Radia has produced a woofer that not only moves huge quantities of air at low frequencies but that—quite remarkably—offers flat frequency response all the way up to about 4.5kHz (a claim few if any other subs can make with a straight face). Second, BG Radia’s THX Balanced Bass Line cabinets effectively eliminate problems with cabinet resonance, which can be a huge problems with many box type subs. Even when the BGX-4850 is belting out powerful deep bass, you can put your hands on the BG woofer enclosures and pretty much feel, well, nothing at all. Though I admit that it initially seems a bit strange, it’s a wonderful thing to experience powerful and articulate bass with no cabinet shakes, quakes, or bad vibes of any kind.

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Carson city, NV-based BG Radia Corporation has staked its reputation on building loudspeakers that leverage the strengths of planar ribbon drivers. As listeners familiar with those technologies might tell you, well-designed planar ribbon drivers can, at their best, offer effortless and uncanny clarity, delivering sound so lucid and transparent that it almost defies description. The only catch, really, is that it’s not easy to manufacture ribbon drivers that can reproduce lower midrange/bass frequencies at high volume levels, which has led BG Radia to offer hybrid speakers that use conventional piston-type drivers for lower frequencies and planar ribbon drivers for higher frequencies.

BG Radia’s most affordable and conventional looking hybrid models are collectively known as Z-series speakers—a product family that’s been around for quite a while.

About four years ago I reviewed a surround system based on BG’s first Z-series speakers and found it to be very good, though with the minor caveat that you could sometimes hear discontinuities in transient speed and resolution between the speakers’ blazingly fast planar ribbon tweeters and audibly slower conventional woofers. What would have helped, I thought at the time, was a planar ribbon midrange driver to help bridge the gap in the middle. And as it turns out a planar ribbon midrange driver is precisely what BG Radia provides in its newest Z-series models—the Z-92 and Z-62. In theory, these speakers should offer greater clarity from top to bottom and a more seamless blend between drivers, and to test that theory I decided to review a surround rig comprised of two Z-92 floorstanders (used as L/R main speakers), three Z-62 L/C/R speakers (used in the center channel and L/R surround positions), plus one of BG Radia’s 210i subwoofers. How does the complete package sound? Read on.

Overview

Consider this speaker system if:
you’re passionate about sound quality and want a movie and music-worthy speaker system that delivers blockbuster dynamics, effortless clarity, detail, and levels of sonic finesse rarely (if ever) heard in commercial theaters. But note: you’ll need good electronics for optimal sound.

Look elsewhere if:
you are pressed for space or would find the ~$7000 system too pricey. The Z-92s and Z-62s are lovely, but can visually dominate smaller rooms. Also, look further if you favor speakers with a soft, diffuse, “romantic” sound; the Z-models invariably give you clarity and detail—in spades.

Ratings (compared to sub-$7k surround speaker systems)

Transparency and focus: 10
Imaging & soundstaging: 9
Tonal balance: 9
Dynamics: 10
Bass extension: 9
Bass pitch definition: 7
Bass dynamics: 9
Value: 9

FEATURES
• Both the Z-92 and Z-62 are three-way, four-driver, bass reflex (i.e., ported) speakers, each featuring dual 6.5-inch mid-bass drivers, a 10-inch x 5-inch Neo10 planar ribbon midrange panel, and a 2.5x3.5-inch Neo3PDR planar ribbon tweeter coaxially mounted in front of the Neo10 panel.
• The Z-92 is a full-range floorstander, while the Z-62 is a somewhat smaller, near-full-range stand-mount monitor/center channel speaker.
• Relative to the original Z-models (which remain in production), the Z-92/Z-62 get improved 6.5-inch mid-bass drivers featuring anodized aluminum cones driven by “double-gap” motors with Neodymium magnets.
• The Z-92 and Z-62 offer gorgeous, real wood veneers with options for light maple or black ash finishes.
• The Z-92 and Z-62 both offer—get this—a lifetime parts and labor warranty.
• 500-watt 210i subwoofer provides dual 10-inch Kevlar woofers arranged in a horizontally opposed, “reactance cancelling” configuration (the woofers face in opposite directions and move outward and inward in unison so that vibration forces exactly cancel out).

SONIC CHARACTER
The Z-92 and Z-62 speakers take big steps forward from the original Z-models in several key areas. First, their new midrange drivers give middle frequencies the same fast, transparent, wide-open sound that made BG Radia’s planar ribbon tweeter famous. This means that transient sounds—drumsticks striking cymbals, guitar picks passing over strings, etc.—burst into life with compelling, realistic immediacy.

            Second, the speed and resolution gap I previously heard between the woofer and tweeter in the original Z-models has now mostly been bridged. This is partly because the new midrange panel fills that gap, but also because the Z-92/Z-62 woofers, which have significantly improved motors, have also gotten better, delivering a more refined, nuanced sound. The result is a speaker where driver voices blend more smoothly than before—with better integration than in many other hybrid speakers I’ve heard.

            While the Z-92/Z-62 speakers sound somewhat bright straight out of the carton, they smooth out nicely after about 50 hours of playing time. Once broken in, they exhibit generally neutral tonal balance, though with faint, occasional hints of upper midrange/lower treble emphasis—characteristics some listeners think enhances clarity, but that tug at your ears to disrupt 3D imaging just a bit.

            But the best part of these speakers, by far, is their midrange, which is smooth, evenly balanced, and full of detail and nuance. Bass is rich and very well weighted, but perhaps just a bit under-damped so that low notes—the deep throb and growl of a vigorously plucked acoustic bass, for example—exhibit more bloom than is, strictly speaking, realistic. This partly has to do with the bass performance of the Z-92/Z-62 speakers themselves, but also with the sound of the 210i sub. The 210i goes low and is powerful, but for its price, I wish it delivered a more taut and defined sound (which BG Radia’s flagship BGX-4850 in-wall sub does, by the way).

            Dynamic prowess is a major strength of the entire BG Radia system—one that differentiates it from many others in its class. There’s an old adage that says you can get sonic subtlety or robust dynamics in a speaker system, but probably not both at once. But with this BG Radia rig, you can. The Z-92/Z-62/210i combo sails happily through large-scale sound effects and musical crescendos at volume levels that would make many systems beg for mercy—a quality that I and that many guest listeners found thoroughly thrilling.

An important hint: The Z-92/Z-62 system sounds very good without any EQ at all, but if you want to hear this system taken to the next level, try using it with electronics that feature the Audyssey MultEQ room/speaker equalization system; the synergy is breathtaking. Because the Z-92/Z-62 speakers are quite good to begin with, the changes you’ll hear might at first seem small, but their overall effect is not. With Audyssey EQ in play, the speakers’ slight upper midrange forwardness goes away and the bass tightens up and becomes better defined—all without losing any transparency or dynamic clout. The net result is that this already very good speaker system becomes even better, with smoother sound overall and surround imaging that’s more pefectly seamless.

MOVIE PERFORMANCE
One film whose soundtrack shows off a plethora of the system’s strengths is Clint Eastwood’s brilliant Letters from Iwo Jima (see Jon Valin’s “Best Film’s of the New Millenium” for a capsule review of this movie). Few films offer more striking contrasts between heartbreakingly quiet, soul-searching moments and gargantuan battle scenes—a spectrum the BG Radia system handles with authority and poise. In the conversation where Saigo argues with Shimizu that the Emperor is better served by soldiers who live to fight rather than by those who commit suicide, for example, the BGs let you hear and feel the desperate, persuasive edge in Saigo’s voice. Yet in larger scale scenes, such as the one where a machine gun emplacement takes a direct hit, the system can reproduce shock waves so violent that they smack listeners in the chest, pinning them to their seats.

           Finally, the BG Radia systems ads power and impact to the scene where we see Japanese soldiers hunkered down in caves, cringing as American artillery shells fall closer and closer to their position. What makes the scene so powerful is that we hear explosions that seem to encircle us, first from afar and then from close range—an effect the system renders with superb surround imaging. Tension builds almost to the breaking point as shells land close enough for the soldiers ( and for us) to hear the fierce, metallic “crack” of detonations almost directly overhead. It’s a scene to make one’s blood run cold, made even more powerful by the BG Radia rig’s ability to remain clear and composed at higher volumes.

MUSIC PERFORMANCE
It takes just one great jazz recording—namely, The Jimmy Cobb Quartet’s Cobb’s Corner [Chesky, Multichannel SACD]—for you to realize that there is more to this system than monster dynamics or the sturm und drang of battle scenes. Try listening to “My Foolish Heart,” and you’ll be struck by the way the Z-92s captures the sweet yet incisive bite of Roy Hargrove’s solo trumpet, which sounds very realistic both in size and timbre. The speakers convey the sense of notes forming with within the horn’s interior and then bursting forth through its brass bell; it’s a captivating sound. Off to the right side of the stage, you’ll hear Cobb’s deft, sure brushstrokes on drums and cymbals. The system does a great job of capturing their delicate, filigreed sound and of expressing the quiet, masterful intensity of Cobb’s playing. In short, the system retrieves deep layers of musical information that other speakers might underplay or simply leave behind.

Bottom Line:BG Radia’s Z-92/Z-62 surround system may not be the slam-dunk “best product” product in its class, but it can certainly compete with the strongest systems I’ve heard in the sub-$7K price bracket, which is saying a mouthful. The system brings distinctive strengths to the table, including superb treble and midrange detailing, a highly nuanced sound, good top-to-bottom driver integration, and the ability to serve up killer dynamics on demand. Dropping close to seven grand on a speaker system might initially seem like an over-the-top luxury, but once you live with the BG Radia system for a few weeks the idea will make perfect sense.

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I've reviewed many excel- lent in-wall speakers, but none quite like the new Radia R-800 in-wall speaker from BG. With 24 drivers in each speaker, this giant stands almost 7 feet tall and is clearly designed for extreme listening—extremely satisfying listening, that is. Each speaker has two 8-inch woofers mounted at the top and bottom, six Neo10 planar-ribbon midrange panels, and 16 Neo3PDR planar-ribbon tweeters in a vertical-line array pattern. An outboard amplifier, the BGA-2500, which is included with a pair of Radia R-800s, powers the two woofers.

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This was an exceptionally ambitious review, but one I was eager to start. My first preview of the Radia R-800s at CEDIA 2005 in Indianapolis was very convincing. I was glad to have the assistance of Ed Jaeger, president of BG, and Fred Yando, vice president of sales, to help me install and set up the Radia R-800 speakers. In fact, I couldn't have unpacked, moved, or installed them in the walls without their help. Beware, because, once they were installed, their appearance in my living room was formidable. If the room didn't have high ceilings, they wouldn't have fit as well as they did.

If their appearance is formidable, their sound quality is awe-inspiring. I've reviewed other BG in-wall speakers and was pleased with the sound quality, which entailed a clean, open midrange and excellent high-frequency detail. But the Radia R-800s define a new standard. Almost immediately, they produced a you-are-there sense of midrange clarity and presence, as well as high frequencies that were pure and uncolored. Each instrument and vocal element was easy to distinguish from others in the soundstage. Detail and definition was outstanding, with a strong center image. Since these speakers were shipped fresh from the production line, their sound quality continued to improve after several hours of breaking in.

606BG.7.jpg 606BG.1.jpg In particular, vocals were strikingly clear, creating a feeling of immediacy and intimacy with the music, as if I were listening to a live performance. With a new recording from Renée Fleming, Haunted Heart (Decca Records), the speakers revealed every detail and nuance in her voice and breath, which helped convey the sad emotions present in many of the songs. The piano sounded as if it were in the room, with a solid foundation of bass and newfound clarity in the midrange and higher frequencies. The Voices Unbound DVD-Audio (AIX Records) by Zephyr showcased two of the best examples of vocal alacrity in the Radia R-800s: "Now Is the Month of Maying" and "Le Chant des Oyseaux." They are a cappella recordings in the round, with a single microphone placed in the center of a ring of vocalists. When I played these tracks in multichannel mode with the rest of the speakers in my system, the voices' transparency and dynamic range were amazing, as if I were seated in place of the microphone. The sound was enveloping, detailed, and accurate.

The Radia R-800s do what any good speaker should: They allow you to hear the music, not the speaker. They are incredibly transparent. Many speakers force you to listen—they have a so-called in-your-face sound—but the Radia R-800s let you listen. They connect you with the music and let you pick out various details and elements of a recording as you wish. There are only two other speakers I've had in my home that impressed me this way: the KLH Model 9s (electrostatic speakers made in the 1950s) and the Dahlquist DQ-10s (phase-coherent speakers made in the 1970s).

Don't be surprised if the Radia R-800s reveal weaknesses in some recordings. As much as I enjoy listening to older discs, these speakers bring out the best and worst qualities in a recording. This was evident in Django Reinhardt's duet with Stephane Grappelli in a 1940s-era monaural recording, Djangology (Snapper Music). As you might expect, the lack of dynamic range was immediately exposed. It's like driving a high-performance sports car with a tank full of the cheapest grade of gasoline.

The Radia R-800s also exhibited a unique characteristic I've not encountered before: When playing music, especially vocals, they retained a strong sense of clarity and detail, even when I was listening from an adjacent room.

606BG.3.jpg The Radia R-800s are the first in-wall speakers I have auditioned that do not need a subwoofer, although BG offers an in-wall subwoofer, the Radia R-88, with two 8-inch woofers. Without a subwoofer, bass response was tight and extended in every music disc and movie soundtrack I played. The bass track in James Taylor's "Line 'Em Up," (Hourglass SACD, Sony Music) sounded authoritative, well defined, and solid, as did "Why Can't It Wait Till Morning" from The Best of Fourplay (Warner Brothers Records). The separate amplifier, the BGA-2500, that drives the two long-throw 8-inch woofers in each speaker employs BG's BASH technology, using a switching power supply and a discrete analog output stage for high efficiency and very cool operation. (The BGA-2500 is available with or without rack-mount ears.) Since the midrange planar driver's crossover is set at 250 hertz, you can drive the rest of the system with an amplifier or receiver, and BG recommends power output of 100 to 250 watts per channel to adequately handle musical peaks. The Radia R-800s have a rated sensitivity of 93 decibels and are capable of a claimed maximum SPL output of 120 dB. I don't think I achieved that level, but, even at high levels, the Radia R-800s retain their high degree of clarity and detail.

I only enjoy watching movies with a good sound system, and, in my opinion, the quality of the sound is more critical than that of the picture. I'm in the process of acquiring an LCD flat panel, and, in the meantime, I'm using a 19-inch CRT TV. Although listening to 7-foot-tall speakers and watching a small TV was a sensory disconnect, the Radia R-800s more than compensated for the small picture size. With the Radia R-800 speakers, it seemed as if I were seated in a widescreen cinema when watching the March of the Penguins and Crash DVDs, two very different but equally compelling films with full, enveloping soundtracks. My 19-inch screen suddenly seemed like it was 19 feet.

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The Radia R-800 speakers present a very wide, tall, deep, three-dimensional soundstage with pinpoint imaging. The soundstage makes the musical presentation sound large, enhancing the feeling that you're listening to a live performance. The wide sweet spot is also ideal for large rooms and off-axis listening where everyone may not have the best seat.

Construction Quality
The construction quality of the Radia R-800s is excellent, with a steel frame complemented by a finely machined aluminum baffle. Each speaker secures to the wall with 12 dogleg clamps, six on each side, and the grille slides into a channel along the sides of the frame for a clean appearance.

The Radia R-800s are suitable for new construction or retrofit installations. BG strongly recommends cavity bracing with construction adhesive and/or building dedicated back boxes or enclosures for the speakers, and I agree. The woofers are capable of moving lots of air, and, unless the cabinet or wall cavity is very solid and well sealed, vibrations and resonance are inevitable. I used an entire tube of caulking with drywall screws spaced every 6 inches on each speaker with good results but still had a few rattles. If I were to install them permanently, I would build back boxes, brace the walls, and seal every joint. Make sure your installer does the same. The benefits will become evident in solid bass reproduction.

In Summary
The BG Radia R-800 speakers are a giant step forward in architectural loudspeakers. Priced at $12,000 per pair (including the external amplifier) they are ideal for installation in a dedicated media room. The Radia R-800s aren't for everyone, but, fortunately, BG has introduced a line of five new Radia in-walls that use the same drivers and design principles with similar sound qualities and more affordable pricing. The new, smaller models are also certain to please those who must convince a wary spouse. But, if you have a large room or theater and want outstanding audio performance, don't overlook the Radia R-800s. Describing the sound quality of the BG Radia R-800s with words doesn't match the experience of hearing them. I can only imagine what a multichannel system with five Radia R-800s would sound like—now that would be extreme listening.

Highlights
• Full-range in-wall speakers with planar-ribbon midranges and tweeters in a vertical-line array
• Excellent detail and definition
• Clean and open-sounding midrange performance
• Solid, well-defined bass response

At A Glance: BG Radia R-800 In-wall Speakers

606BG.5.jpg Features
Number of Channels: 2
Power Rating (watts per channel): 500
Frequency Response: 20 Hz–20kHz
Dimensions (H x W x D, inches): 3.95 x 16.9 x 14.7
Weight (pounds): 17.5
Price: Included with speaker pair

Connections
Inputs: Line-level RCA (2)
Outputs: Line-level RCA (2), high-level speaker
outputs with five-way binding posts (2 pair)

Speaker: Radia R-800
Type: Three-way in-wall
Tweeter (size in inches, type): 3 x 2.5, Neo3PDR planar-ribbon panels (16)
Midrange (size in inches, type): 10 x 5, Neo10 planar-ribbon panels (6)
Woofer (size in inches, type): 8, long throw (2)
Nominal Impedance (ohms): 4
Recommended Amp Power (watts): 100
Available Finishes: White
Dimensions (H x W x D, inches): 81.5 x 11.58 x 3.7
Weight (pounds): 68
Price: $12,000 per pair including BGA-2500 amplifier

Ratings: BG Radia R-800 In-Wall Speakers

Build Quality: 96
Well built with a steel frame and machined aluminum baffle

Value: 96
One of the most expensive in-walls, but well worth it for a no-holds-barred media room/home theater

Features: 95
Separate bass amp reduces demand on main amp or receiver

Performance: 98
Excellent transparency, detail, and definition, especially with vocals

Ergonomics: 93
This is not a speaker for the do-it-yourselfer. Have them professionally installed with extra wall and cavity bracing

Overall Rating: 96
These huge BG in-walls employ planar-ribbon drivers to remarkably transparent ends. They can be both subtle and powerful.

General Information
Radia R-800 In-Wall Speakers, $12,000/pair
BG Corp.
(775) 884-1900
www.bgcorp.com

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Last summer, John Atkinson and I were playing a jazz gig poolside at my local club, and during a break we began discussing equipment. As JA adjusted his microphones and I became increasingly nervous about the running, jumping kids splashing chlorinated water on his Nagra digital recorder, he asked me if I'd like to review the Z1 loudspeaker from BG Corp. "It's an interesting little bookshelf speaker featuring a ribbon tweeter." Hmm—an affordable bookshelf speaker matching a ribbon tweeter to a dynamic woofer? Very interesting. "Sounds good," said I, and resumed my ivory duties.

Company
Bohlender-Graebener Corporation, now known as BG Corp., is a Nevada-based company that since 1994 has produced a broad range of loudspeakers, all of them featuring BG's proprietary ribbon-tweeter technology. In addition to a line of conventional speaker pairs—the flagship of which, the Radia 520i ($4000/pair), Larry Greenhill reviewed in December 2004—BG manufactures a wide range of in-wall, on-wall, and custom-installation speakers. The Z1 ($499/pair), the first model in BG's affordable Z series, is a fairly unassuming shielded bookshelf speaker in which BG's ribbon tweeter is coupled with a 5.25" aluminum-cone woofer.

BG feels strongly that a ribbon driver is the best way to reproduce midrange and high frequencies. The mass of BG's tweeter diaphragm is 30–50 times less than that of a typical dome tweeter. Thus, according to BG, the tweeter's mass is comparable to that of the air that is vibrating along with the diaphragm. It can be energized more quickly, stores much less energy and inertia, can stop vibrating sooner, and its decay pattern is cleaner.

BG credits two major developments in materials science over the last two decades that have enabled further advancement in ribbon technology. First, neodymium has become less costly, making it viable for use in the motor structure of ribbon tweeters. Magnets made of neodymium have magnetic energy 20–30 times greater than the ceramic magnets used in the ribbons of the 1970s and '80s. Second, BG makes their diaphragms of Teonex film, developed by DuPont in the 1990s. BG feels that Teonex can withstand higher temperatures and is stronger than the Mylar film used in earlier ribbon designs.

BG set out to design a ribbon tweeter with smooth frequency response, low noise, wide horizontal dispersion, and high efficiency, all at low cost. Their patented ribbon design uses fewer magnets than conventional ribbons by eliminating side magnets positioned close to the clamping frame and, instead, placing strips of acoustically semitransparent absorptive material close to the diaphragm in the area between the diaphragm and the metal plates. BG says this allows them to largely retain the transducer's necessary sensitivity while providing sufficiently wide horizontal dispersion.

Sound
I placed the Z1s on my trusty Celestion Si stands, loaded with sand and lead shot. Although BG felt there would be a slight improvement in sound on-axis with the speakers' grilles removed, I got the most timbrally natural sound with them left on, which is how I did most of my listening. The difference was slight, however.

The Z1's detailed, delicate, coloration-free, and holographic midrange presentation impressed me with all vocal recordings. The notes I took while listening to the acappella introduction of Brian Wilson's "Our Prayer," from SMiLE (CD, Nonesuch 79863-2), read the same as my notes for Madeleine Peyroux's "Hey, Sweet Man," from Dreamland (CD, Atlantic 82946-2): "gorgeous, silky, holographic vocals." The Peyroux track also had me fixated on Marc Ribot's dobro; the extended and detailed high-frequency capabilities of the Z1's ribbon tweeter revealed levels of detail, delicacy, and immediacy that I'm not used to hearing from a $499/pair speaker.

The Z1's resolution of the high frequencies of vocal sibilants was so accurate that I felt I was listening to Janis Ian's Breaking Silence (CD, Analogue Productions CAPP 027) for the first time—a tough thing to do, considering that it's the most-played recording I own. The Z1's combination of low-level dynamic articulation and what appears to be a remarkable tweeter let me hear tactile nuances from this recording that I'd not noticed before through any speaker costing less than $2000/pair.

I began to mine my collection for recordings of acoustic stringed instruments. Don Fiorino's lotar—a fretless, four-string Moroccan lute—on Attention Screen's La Tessitura (CD, Hojo HOJO 10) sounded as if it was in the room with me. My listening notes: "Texture! Timbre! Transients!"

The Z1's low-level dynamic capabilities made me want to listen to woodwinds and brass as well as strings. On his Way Out West (CD, JVC VICJ 60083), Sonny Rollins' tenor sax was incredibly realistic in timbre, texture, and dynamics. Similarly, the saxes and trombones on the Jerome Harris Quintet's recording of Duke Ellington's "The Mooche," from Editor's Choice (CD, Stereophile STPH016-2), bloomed with a sense of organic and linear dynamics, with no trace of compression. The ride cymbals during the horn solos also seemed very lifelike.

The Z1 was also able to articulate transients with senses of speed, delicacy, and attack that I've come to associate only with much more expensive speakers. The transient attacks, decays, and timbre of Gary Burton's vibes on his first album, New Vibe Man in Town (LP, RCA LSP-2920), were sufficiently lifelike that I dropped my notebook. My mouth was agape as I focused on Burton, then an 18-year-old wonder trained in the classical marimba, trading fours with Joe Morello's brushes on "Joy Spring."

One acid test I use to test a speaker's high-frequency articulation is "Tiden Bar Gor," from Depth of Image (CD, Opus3 CD 7900). The beginning of the track features the interplay of two acoustic guitars, one steel-string, one nylon-string. With speakers of exceptional HF resolution, it's pretty obvious which guitar is which; through many affordable speakers, they can sound quite similar. With the BG Z1, the difference between the two guitars' textures was as easy to delineate as it is with my $12,000/pair Nola Circes.

One aspect of the Z1's HF performance concerned me, though only with certain recordings. If I played music with significant high-frequency energy and fast transients, such as the more pyrotechnic piano solos on the Jamie Saft Trio's Astaroth (CD, Tzadik TX 7348), the highs seemed to have an "etched" quality, particularly when the speakers were driven hard. But this, the Z1's sole deviation from neutrality, reared its head only occasionally.

The Z1's midbass and upper-bass performance was quite natural. A slight bit of warmth in the midbass was evenly distributed across a broad frequency range and did not detract from the musical experience. Ray Brown's bass solos on Way Out West were warm but natural, it was very easy to follow the pitches, and there was no sense of sluggishness or overhang.

Although the Z1 never sounded bass-shy, it didn't seem to have much in the way of low-bass extension. The bass drums on Antal Dorati and the London Symphony's recording of Stravinsky's The Firebird (CD, Mercury Living Presence/Classic SR 90226) and the CD layer of David Chesky's Area 31 (SACD, Chesky SACD282) sounded natural but did not shake the room much, and the lower register of the organ pedals on John Rutter's Requiem (CD, Reference RR-57CD) were missing in action.

To achieve a well-balanced midbass presentation that didn't sound bass-shy, I had to follow JA's setup recommendations. Normally, I place bookshelf speakers on stands anywhere from 2' to 4' from the front wall, depending on the speaker. To achieve a natural bass balance with the Z1s, I had to place them 1' from the front wall, which affected their soundstage presentation. On any well-recorded acoustic music, the speakers "disappeared," placing pinpoint holographic images across the soundstage. However, when the Z1s were only 1' from the front wall the depth become somewhat foreshortened. At 2' from the wall the soundstage depth increased significantly, but then the speakers sounded a bit bass-shy. This effect was sufficiently noticeable that I preferred the sound of the Z1s closer to the wall rather than out in the room.

For a bookshelf model with limited low-bass extension, the BG Z1 performed admirably as a rock speaker, and at fairly high volume levels. Wandering down memory lane, I cranked up "Jingo," from Best of Santana (CD, Columbia CK 65561), one of my favorite tunes from the set list of my old high school band, and started twitching around the room in my T-shirt and shorts, playing a mean air B-3. (My wife and kids weren't home. The dog looked at me strangely and left the room.) I had a similar reaction to the dramatic power and authority of Kraftwerk's Minimum-Maximum at 95dB (CD, EMI ASW 60611).

In fact, almost all the recordings I threw at the Z1 sounded natural and involving. Bill Frisell's idiosyncratic arrangement of "I Heard It Through the Grapevine," on East/West (CD, Nonesuch 79863-2), was devoid of coloration. This live recording sounded so immediate that I felt I was sitting in Yoshi's club in Oakland listening to the band.

Comparisons
I compared the BG Z1 ($499/pair) to the NHT SB-3 ($600/pair), the Nola Mini ($695/pair), and the Epos M5 ($650/pair).

The NHT SB3's rich midrange was similar to the BG's, but with much less detail in the midrange and highs. The NHT's bass extension and high-level dynamics were more impressive than the BG's, however. The Epos M5 revealed more midrange detail than the BG Z1, and had a tighter, slightly less warm midbass. The M5's highs were also rather extended, but the Z1 was a bit more detailed. The Nola Mini had better resolution of midrange detail than the BG Z1, and even better articulation of low-level dynamics. The Mini's highs were as extended as the Z1's, but the BG's highs seemed a bit more delicate. The Nola Mini's bass extension and high-level dynamics were superior, however.

Summing up
Overall, the BG Z1 was a top performer on a wide range of music—it played a lot of music for its price. The Z1's ribbon tweeter is a detailed and colorless transducer as long as it's not pushed too hard with complex material, and appeared to integrate seamlessly with the speaker's dynamic woofer over a broad range of program material. You may have to experiment with speaker placement, however, to achieve your optimal blend of bass extension and soundstage depth.

I congratulate BG Corp. on producing a cost-effective loudspeaker for audiophiles on a budget who nonetheless seek something a bit more innovative than "two dynamic drivers in a bookshelf box." Excellent work!

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Certain loudspeaker manufacturers are known for "signature" speaker technologies, such as Klipsch for its horn drivers or MartinLogan for its curved electrostatic arrays, and Bohlender-Graebener is best known for using planar magnetic or "ribbon type" drivers. Based on the few, too-brief listening experiences I've had with them, Bohlender- Graebener's full-size planar magnetic speakers struck me as promising and impressive performers, but whose pricing put them beyond reach of some listeners. Happily, though, Bohlender-Graebener offers a great option for budget-minded enthusiasts: the affordable Radia Z-series—speakers that use hybrid combinations of traditional, piston-type bass/midrange drivers and ribbon tweeters. Does the hybrid approach work? There is certainly good reason to think so, judging by the comments made by my colleague Neil Gader in his recent review of the Radia Z7 tower-type speaker for our sister magazine, The Absolute Sound. In fact, Neil found the sound of the Radia Zs sufficiently interesting that he suggested I review them for AVguide Monthly, this time evaluating the Z7s as part of the complete Radia Z-series 5.1-channel surround system. And so the idea for this review was born.

The Radia Z surround system comprises the tall, slender Z7 tower type speakers as reviewed in TAS, plus a companion Z5 center-channel speaker, a pair of small Z1 monitors used as surround speakers, and a matching Z Sub subwoofer with built-in 150-watt amplifier. All models in this lineup (save for the subwoofer) feature Bohlender-Graebener's 5 ¼" aluminum-coned mid-bass drivers, proprietary Neo3PDR (Progressive Drive and Radiation) ribbon-type tweeters, and Linkwitz-Riley crossover networks (which allow steep crossover slopes, yet keep drive units in phase with one another through the critical crossover region). This shared driver and crossover technology made for desirable consistency in voicing among all the Radia Z speakers—a factor that really helped this speaker system create smooth, well balanced surroundsound fields during my listening tests. The Radias are supplied with attractive press-on grill frames, but to enjoy all the clarity and openness of which these speakers are capable, you willwant to remove those frames and set them aside. My review samples were covered on all sides (rear panels included) in a gorgeous cherry veneer that received a strong "thumbs up" cosmetic approval rating from my wife and kids.

There's no denying that the Radias are lovely to look at, but are they as easy on our ears? In many respects they are. In the interest of clarity, let me comment first on the semi-full-range Z7 tower speakers, and then on the complete Radia surround system.

Before I first heard the Z7s, I wondered if BG's exotic ribbon tweeters and metal-coned bass/midrange drivers would draw undue attention to themselves, but it took only a few minutes of listening to recognize that the opposite was more nearly the case. Why? First, because the Radias' aluminum bass/midrange drivers sounded notably warm, rich, and smooth-not in any way edgy or metallic (dispelling the goofy high-end audio/home-theater myth that holds that metal drivers produce characteristically metallic sounds). Second, the Radias' signature Neo3PDR ribbon tweeters offered articulate, smooth, and extended treble response, with excellent speed and definition on sharp transients, yet without so much as a hint of aggressiveness or excess brightness (this is a fine tweeter, and one that clearly demonstrates the strengths of ribbon technology). Putting these factors together, the Z7s proved to be, exactly as Neil Gader observed in his TAS review, easy to listen to and offering warm and plentiful (though not particularly tightly defined) mid-bass, a smooth and gently recessed midrange, and classy, well-focused highs.

I found the Z7s did have some shortcomings, particularly in the areas of soundstaging and overall textural continuity—areas where my impressions of the Z7's performance varied somewhat from Neil's. While the Z7s are fully capable of resolving the kinds of subtle spatial cues and details that ordinarily make for good soundstaging, I found their soundstaging decent but not exceptional (falling short of the potential I think the terrific BG ribbon tweeter holds). The problem was that the sound, though clear and finely textured, somehow tended to "cling" to the faces of the Z7s rather than breaking free to produce compelling three-dimensional soundstages. Perhaps this problem was related to the issue of overall top-to-bottom textural continuity. My observation was that BG's aluminum-coned bass/midrange driver and its ribbon tweeter, though each a very good driver in its own right, did not speak with a single, unified voice. Instead, the ribbon tweeter sounded just enough "faster" and more finely resolved than the aluminum bass/midrange driver for there to be some audible discontinuity in the crossover region between the two. In fairness, I should point out that the only reason this issue even comes up is because BG provides us with a ribbon tweeter whose performance stands head and shoulders above that of the high-frequency drive units you'd normally find in speakers in this price range.

Even with these minor drawbacks (and they are minor), I do concur with Neil Gader's generally favorable assessment of the Z7.

The game becomes much more interesting, however, once you step up from a stereo pair of Z7s to the full Radia Z surround system, as several performance factors start working in your favor in a big way. First, you suddenly have 5.1 (rather than just two) similarly voiced Radia Z speakers jointly sharing responsibilities for presenting three-dimensional soundstage information. I found this change alone carried unexpectedly big benefits, greatly improving the Radia Zs' ability to create believable three-dimensional soundstages. The improvement was quite clear cut on recordings such as the beautiful "Canon" track from Béla Fleck and Edgar Meyers' Music for Two [Sony Classical]. This live recording captures a haunting duet in the form of an intricate round (think "Row, Row, Row Your Boat" on steroids) between Meyers' acoustic bass and Fleck's banjo. As heard through the Z7s alone, this recording sounded a little flat or two-dimensional; but the full Radia Z surround system created a much more believable illusion of a real banjo and bass playing in a real hall, and in the presence of a real audience. Once you distribute the imaging workload across five voice-matched Z-series speakers and a good powered subwoofer, imaging weaknesses are minimized, and the Radias' inherent smoothness and clarity can assert themselves, significantly improving three-dimensionality.

But the Radia Z surround system also shows improvements in other important areas—particularly in terms of overall textural continuity (or top-to bottom evenness of voicing). Both Neil Gader and I noted that the Z7s showed a slightly recessed midrange sound; but through the full Radia Z surround system, that slightly recessed quality largely went away, and the surround system's midrange sound seemed smoother, too. I noticed these improvements, in particular, on recordings that highlighted (and clearly exposed) the sound of female voices, such as the "Por Causa de Você" track from Rosa Passos and Ron Carter's beautifully recorded Entre Amigos [Chesky]. Passos' voice has a quality that is at once dusky and full-bodied, yet also delicate and ethereal, and the Radia Z surround system did a beautiful job of capturing those elusive qualities with a wonderful touch of human warmth.

Compared to the sound of the Z7s, then, the Radia surround system's midrange voicing sounded more fully fleshed-out and better balanced with respect to the system's warm, rich mid-bass. Bass quality in the surround system was also improved, thanks to the Z Sub powered subwoofer. While the Z Sub is neither the last word in bass articulation nor definition, it sounds more powerful than its power rating would suggest, and it significantly extends the low-frequency reach of the system with bass voicing that is consistent with, and better controlled than, that of the Radia Z main, center, and surround speakers. On music or film soundtracks where the Z7s' bass could sound a little "woolly" and overblown—for example, on the cannon fire in Master and Commander— The Far Side of the World [20^th Century/Fox]—the Z Sub added a welcome measure of bass power, extension, and control. Thus, on Master and Commander, the Z Sub enabled me to hear the initial crack and then thunderous low-frequency roar as the sound of the cannon fire carried over the water, and then—a split second later—the shuddering shockwaves of cannonballs sizzling through the air, just over my head.

Finally, the full Radia Z surround system seemed to mitigate, though not completely eliminate, problems of textural discontinuity between the Radia tweeter and bass/midrange driver. Perhaps this improvement resulted from the simple fact that, in a 5.1-channel surround system, there are more speakers to share the workload, meaning that individual speakers do not need to play as loudly as they would in a stereo system to achieve a desired volume level. With the volume levels of individual speakers in the systems reduced, textural discontinuities became less noticeable, even as the Radia Z's natural smoothness and clarity came shining through. This improvement made a worthwhile difference on richly detailed recordings, such as jazz guitarist Tuck Andress' stunning solo album Reckless Precision [Windham Hill]—a recording where textural subtlety means everything, and where the Radia surround system's better-integrated voicing helped create, and then maintain, the illusion that a master jazz guitarist had come to play a private concert in my living room.

To synopsize, let me say that the Bohlender-Graebener's Radia Z surround system preserves everything that is good and right about the Z7 floorstanding speaker, while offering meaningful improvements in several important areas. You'll still enjoy the mid-bass warmth, midrange smoothness, and treble clarity of the Z7, but now with greater three-dimensionality, better midrange balance, tighter and more extended bass, and somewhat more comfortable integration between BG's superb ribbon tweeter and its aluminum bass/midrange driver. Importantly, the Radia Z surround system is easy to drive, not at all fussy about associated electronics, and capable of performing equally well on films and music (a claim not all surround speaker systems can make).

This system's sound won't appeal to everyone, nor will it provide quite the sort of top-to-bottom focus and lucidity you might hear from the larger (but much more expensive) Bohlender-Graebener planar magnetic designs. But for those who have grown weary of speakers that deliver icy, etched, and aggressive sound in the name of definition and detail, the Radia Z system offers an oasis of sonic warmth, smoothness, and relaxation. At a total of just under $2350, it also very competitively priced. As always, we strongly urge you to hear the Radia Z system for yourself, so that you can determine whether its distinctive magic works for you.

Specifications

Manufacturer's Suggested Retail

Price: Radia Z7 mains, $999/pair;

Radia Z5 center channel, $399/each;

Radia Z1 surrounds, $499/pair; Radia
Z Sub, $599/each; Total Radia Z 5.1-
channel system price: $2,496

Type; Mains: Floorstanding, 2-way, 3-driver, bass reflex (40" x 8.75 " x 10.25", 42 lbs.)

Center channel: tabletop, 2-way, 3- driver, bass reflex (10.7" x 6.8" x 9.5", 22 lbs.)

Surrounds: Powered subwoofer: Floorstanding (18.1" x 12.6" x 16.54", 56 lbs.)

Driver Complement L/R: (2) 5 ¼ '' aluminum bass/midrange drivers; (1) Neo3PDR ribbon tweeterDriver

Complement Center: (2) 5 ¼ '' aluminum bass/midrange drivers; (1) Neo3PDR ribbon tweeterDriver

Complement Surrounds: (1) 5 ¼ '' aluminum bass/midrange driver; (1) Neo3PDR ribbon tweeterDriver

Complement Subwoofer:(1) 10" Paper composite cone woofer with 3" voice coil and high excursion rubber surround

Integral Amplifier Power for Subwoofer: 150 watts

Subwoofer Operating Principle: Bass Reflex

Sensitivity L/R 89dB

Sensitivity Center 89dB

Sensitivity Surrounds 88dB

Impedance L/R 4 ohms

Impedance Center 4 ohms

Impedance Surrounds 8 ohms

Manufacturer Information

Bohlender-Graebener

1780 Forrest Way

Carson City, Nevada 89706

(888) 875-2627

www.bgcorp.com

Associated Equipment

Sony STR-DA-9000ES AVR; Sharp SD-HX500 1-Bit Digital AVR/universal player; Integra DPC-8.5 universal player; Pioneer PDP-505 HD plasma display; Chang Lightspeed CLS-HT 1000 Mk II power-line filter; Synergistic Research X2 interconnect, subwoofer, and speaker cables (featuring proprietary Synergistic active shielding system). Equipment Review

Chris Martens

AVguide Monthly

www.avguide.com

Archive: 1

The Radia Series speaker system is the latest development from what can be considered a seriously thick branch in the speaker-manufacturing tree. You may not be too familiar with the Bohlender-Graebener name; but, when it comes to hybrid planar magnetic driver technology, the name isn't uttered without a good deal of respect.

A couple of years after BG was launched, HT reviewed an early iteration of the present review system. The individual speaker nomenclature has not changed from the earlier model, except for the addition of the letter "i" (for "improved") to each speaker designation. According to BG, improvements include "new advanced Linkwitz-Reilly crossovers for improved balance and reduced phase distortion and updated planar ribbon drive units for higher efficiency, lower distortion, and extended frequency response."

What distinguishes the planar ribbon driver from more-traditional speaker technologies is simply this: Most of the frequency range is generated not by a cone driver but by a flexible membrane. The membrane is bonded with conductive traces and then suspended in a magnetic field. When the conductors are energized by an amplifier's signal, the membrane responds by moving in a push-pull fashion as the signal varies. Voilà! Sound.

For this review, I partnered the Radia system with a Samsung LCD monitor, an Onkyo DV-SP800 universal disc player, a Parasound Halo C 2 processor, Sunfire Cinema Seven Signature Edition and Simaudio Moon Aurora seven-channel amplifiers, and Kimber 8TC speaker wire.

The Speaker Array

The 520i, used as front left and right speakers, features a 50-inch-tall, planar magnetic line-source and two 6.5-inch cone drivers located in the base. This configuration allows for a claimed effective frequency range of 70 hertz to 20 kilohertz (–6 decibels, half space). The loudspeaker base is constructed of an MDF enclosure that houses the two long-throw cone drivers and the crossover components. Jutting from this base is a flat-black anodized-aluminum tower containing the planar driver. The 420i, used here for surround duties, is essentially a 10-inch-shorter version of the 520i. It claims an identical effective frequency range. The crossover design in both the 520i and 420i speakers divides frequencies at 350 Hz, allowing every frequency above the midbass to be handled by the planar drivers.

If you think the 520i and 420i need room to breathe, you'd be right, but wait until you consider the center channel, the 220i. This massive beast significantly outspans the width of a conventional 32-inch CRT and would best be situated atop a speaker stand positioned just below the viewing area. The MDF cabinet encases two 6.5-inch woofers, two 8-inch planar midrange drivers, and one 3-inch planar ribbon tweeter. Starting from the outside edge, you'll find first the woofer, then the midrange ribbon, then the tweeter ribbon. According to our previous review, the original center channel carried a soft dome tweeter in an effort to "provide broader horizontal dispersion for the high frequencies." On a subjective level, it appears that the "i" modifications have eliminated the need. In fact, the use of the tweeter ribbon may allow the frequency response to soar into a claimed 25-kHz region, beyond the range of audibility but de rigueur in today's multipurpose (SACD, DVD-Audio, and DVD) environments.

The 220i is said to drop down to 50 Hz, a point roughly 10 Hz above the pressure level generated by the lowest open string on an upright bass, which goes a long way toward explaining why B-G released their own complementary subwoofer earlier in 2004. At 14.5 inches high by 13.5 wide by 17.5 deep, the Radia 210i subwoofer is a relatively compact enclosure that manages to house a pair of 10-inch Kevlar drivers and a 500-watt BASH amplifier. The 210i breaks the rectangular standard pervasive in most subwoofer designs: Along one plane, you'll see approximately one-fourth of a rigid cylinder breaking out of the side. More than an aesthetic conceit, this cylinder houses both drivers, which are situated so that their cones face opposite directions while being wired in phase. According to B-G, "Recalling Newton's Law, where for every action there is an opposite and equal reaction, the movement generated by the woofer's cones causes the reactive forces of each woofer to effectively cancel one another." B-G has trademarked their approach to woofer placement as a Reactance Canceling Design. The subwoofer's onboard amplifier is said to allow for transient peaks of well beyond 1,000 watts, with the net result that the drivers can travel more than 2 inches, equaling the output of a "conventional 14-inch subwoofer."

Tricky Setup

Although my listening room is oddly shaped, I've had little difficulty getting maximum replay through most conventional cone-driver speaker arrays—including soundstage accuracy, vertical dispersion, and tight bass output. At the very least, I know how to determine when the room interferes with a particular setup. That was not the case with the Radias. That's because B-G calls for specific speaker placement, going as far as providing a schematic with angles and distances recommended in relation to the seating position. The surrounds, for example, need ample breathing room away from corner boundaries; also, the listener is warned to avoid placing the surrounds to the sides of the listening area and instead is told to position them in a "subtended angle" between 90 and 120 degrees, a minimum of 7 feet on either side behind the seating position.

After trying to max out the situation at home without success, I eventually dragged the whole kit and caboodle to our studio in order to generate a fair and balanced review. B-G's directions, by the way, are exceptional, and studio setup proved to be a snap. The soundfield snapped into focus, too.

Sound: The Point of It All

The first thing I noticed was that the system has incredible resolution of micro-details. The Diva sequence in The Fifth Element sounded particularly spectacular. You could readily hear the breathy quality of the Diva's voice, her soaring range, the sharp metallic nature of ammunition puncturing sheet-metal ductwork, and the depth of the massed cellos and basses wallowing in the background. Initially, the system sounded a bit compressed, but this characteristic was attenuated significantly when I used the Simaudio Moon Aurora amp, which allowed the system to eke out even more micro-details.

Of course, excellent transient response can be a given with a panel-based system like this one. It is, rather, the quality of the design as it relates to nuance. Take, for example, the underrated film Underworld. The mood is dark, at times crackling with the energy of electricity and thunderclaps positioned variously around the room and at other times with the aural sense unique to rain falling on concrete. The Radia system captured these moods, subtleties, and sound positions without fail. Hearing the sound of skin split and bone crack when a human transforms into a werewolf is hair-raising stuff. Without such aural revelations, the movie can seem threadbare; however, with a good system like the Radia, the movie becomes a gripping tale.

The Radia system can fill a soundstage quite well, behave itself with music, and portray width and height when necessary. To split hairs, I have heard a bit more depth in the soundstage with other similarly priced systems. Also, while bass wasn't lacking, as evidenced by the tight thunderclaps in the opening of Underworld, I wondered how an extra Radia sub would have helped generate that oomph factor that moves home theater to another level. Finally, there was the minor issue of the spiked feet. While appealing to the eye as they sat in their brace crossmembers, the spikes would not readily punch through the carpeting and pad when I installed the system in my home. It never felt as if the speakers were fully grounded.

Other than these minor nits, for nearly $11,000, this system is definitely worth a listen if your room is on the large side and you like exotic-looking gear that will transport you into the world of film. In order to squeeze out the greatest amount of information, you'll need to drive the array with an equally competent and sophisticated amp, processor, and universal player. Lesser-quality partners simply will not do if you want to get your money's worth from the Radia Series speaker system.

Highlights

• State-of-the-art hybrid planar technology

• Excellent transient response and engrossing detail

At A Glance: Bohlender-Graebener Radia Series Speaker System

Subwoofer: Radia 210i

Connections:

Speaker- and line-level ins and outs

Enclosure Type: Sealed

Woofer (size in inches, type): 10, Kevlar cones in a reaction-canceling design (2)

Power Rating (watts): 500

Crossover Bypass: Yes

Available Finishes: Black

Dimensions (H x W x D, inches): 14.5 x 13.5 x 17.8

Weight (pounds): 62

Price: $1,499

Speaker: Radia 520i

Type: planar, tower

Tweeter (size in inches, type): 50, planar ribbon

Midrange (size in inches, type): N/A

Woofer (size in inches, type): 6.5, paper cone (2)

Nominal Impedance (ohms): 4

Recommended Amp Power (watts): 50–250

Available Finishes: Black

Dimensions (H x W x D, inches): 70.25 x 9.25 x 13.25

Weight (pounds): 59

Price: $3,999/pair

Speaker: Radia 220i

Type: planar, center

Tweeter (size in inches, type): 3, planar ribbon

Midrange (size in inches, type): 8, planar ribbon (2)

Woofer (size in inches, type): 6.5, paper cone (2)

Nominal Impedance (ohms): 4

Recommended Amp Power (watts): 50–250

Available Finishes: Black

Dimensions (H x W x D, inches): 8.25 x 41 x 12

Weight (pounds): 52

Price: $1,699

Speaker: Radia 420i

Type: planar, tower

Tweeter (size in inches, type): 40, planar ribbon

Midrange (size in inches, type): N/A

Woofer (size in inches, type): 6.5, paper cone (2)

Nominal Impedance (ohms): 4

Recommended Amp Power (watts):50–250

Available Finishes: Black

Dimensions (H x W x D, inches): 58.875 x 9.25 x 13.25

Weight (pounds): 51

Price: $3,799/pair

Archive: 0

Loudspeaker cabinet design has been strongly influenced by home theater. Large floorstanding cabinets, required for reproduction of bass frequencies, are being replaced by tall, graceful towers with small footprints. While these slim speakers fit more easily into home décor and living spaces, to fill out their bass response they depend on being used with the subwoofers that are standard in multichannel systems.

Igor Levitsky, speaker designer for Bohlender-Graebener Corp. (aka BG Corp.), has taken advantage of the slim tower motif in the design of the Radia 520i speaker, which has a 50" midrange-tweeter ribbon driver. This narrow driver offers wider horizontal dispersion than a panel speaker, while suppressing strong early reflections from the floor and ceiling by acting as a line source. A line-source speaker radiates a cylindrical wavefront, which suffers milder propagation losses than does a conventional cone driver. Levitsky mounted the 520i's ribbon driver in a tall, open aluminum frame to minimize cabinet resonance effects.

The 520i's ribbon covers the spectrum above 350Hz and fires through a 30mm-wide slot in an aluminum frame. The ribbon itself consists of a diaphragm of polymer film strung with aluminum conductors, which carry the audio signal, suspended between push-pull magnet arrays. Levitsky complements the ribbon with two 6.5"-cone woofers mounted in the 520i's 7.75" by 13.75" lower enclosure, made from MDF. These provide bass down to 70Hz. The crossover uses modified fourth-order Linkwitz-Riley filters, with an in-phase driver connection.

Some assembly is required before the Radias can be used. The tall, thin towers must be anchored to their flat brass bases with ¼" hex-head screws. Four legs extend out from the base, each tipped with a sharp spike. Top caps are then mounted on each speaker column. (The caps are packed separately so that the 520i box keeps within UPS's maximum package length.) Although not described in the accompanying information sheets, the metal brackets at the back of each plastic cap must be slid under two mounting screws at the top of the speaker column. The front and back grilles can be removed by pulling them up and lifting them out of their black anodized rails—sort of like unzipping a zipper.

Setup & fine-tuning

I set up the Bohlender-Graebener Radia 520i's in the exact spots usually occupied by my reference Quad ESL-989s: 8' apart, 5' from the back wall, and 3' 9" from the side walls. Moving the BGs into position, I was struck by the towers' height (over 70"), narrowness (under 8"), and relative lightness (59 lbs). I did my listening in my lightly damped, rectangular listening room, which is 26' long, 13' wide, and 12' high. Behind my listening chair, the other end of the room opens into a 25' by 15' kitchen. All listening was done with the BGs' grilles in place. For purposes of stability, I left the spikes in the floor stands.

First, I had to decide: Did I need a subwoofer for this review? Without a sub, the BG Radia 520i generated a wide soundstage, with a smooth upper midrange and highs and fast, accurate sound. On first listen, I was surprised and pleased to find that the 520i also had a fast, true upper-bass response. For soloists and for some percussion, I didn't miss the bass extension. But the lack of the deep bass on recordings that feature bass drum and pipe-organ pedal tones made such music less dramatic and involving. In addition, the 520i's two woofers grew mildly distorted when driven extremely hard with bass drum passages or rock music. Deep, powerful bass drum notes, in particular, seemed muffled and distant, and greatly changed in tonality. I decided to listen with and without a subwoofer.

True, I'd used the BG Radia 520i in the final listening sessions for my review of Revel's Sub 30 subwoofer (Stereophile, November 2004). The Sub 30 had been placed in the right rear corner, behind the plane of the Radias. A pair of stereo interconnects ran from the Mark Levinson ML-7a preamplifier to the line-level right and left inputs on the Sub 30's rear panel. The Sub 30's high-pass filter was set to 80Hz and 12dB/octave, its low-pass filter to 80Hz and 48dB/octave, its Contour switch to Music. Interconnects were run from the Sub 30's right and left output jacks to a pair of Mark Levinson ML-2 power amplifiers, which drove the BGs.

When I first set up the Radias with the Revel sub, the phase and channel-identification checks on Stereophile's first Test CD (Stereophile STPH002-2) revealed that the BGs' phase was inverted. Eric Graul, production manager at BG Corp., helped me track down the problem: the Revel Sub 30's electronics inverted phase. When driven directly from the preamplifier, the 520is were in phase. Whenever I added the Revel to the system, I set its Phase control to 180 degrees.

I then used the built-in signal generator, microphone, and virtual spectrum analyzer of a Velodyne DD-18 subwoofer to evaluate the BG 520i's in-room frequency response at my listening position with and without the Revel subwoofer. (Velodyne's technology is not part of the BG 520i's or Revel Sub 30's standard installation packages; see Stereophile, June 2004, p.133.) I set up the Velodyne's calibration microphone on the back of my listening chair at my ear level, 37" from the floor, and set the DD-18's volume control to "0" so that it would put out no audio signal. I then keyed the Velodyne's remote control to display its System Response screen on my TV monitor. This automatically initiates a repeated sweep tone from the DD-18's signal generator, which is then fed into a tape input on my preamp. When I drove the BG 520i without the subwoofer its frequency response showed peaks at 180Hz and 125Hz, falling gradually below that point, to -3dB at 90Hz and -10dB at 60Hz. Adding the Revel Sub 30 extended the response down to 20Hz, ±6dB.

Using pink noise from Stereophile's Test CD 2 (Stereophile STPH004-2) to drive the Radias without the subwoofer, the tonality of the resulting sound varied smoothly and gradually as I moved back and forth and from side to side in my listening chair. I found the Radias' sweet spot in my room to be about 6" wide and 12" deep. To stay within that small spot, I had to sit up and forward in the listening chair. I propped myself in position with two pillows—just moving the chair forward didn't position me properly. Outside this zone, the pink noise dulled slightly. It also dulled when I stood up, but did not vary more when I moved around the room. However, in its narrow sweet spot, the 520i's highs in the pink noise seemed to be fine, or at least equivalent to those I hear with the Quad ESL-989s.

Sound

The BG Radias' strengths were in imaging, speed, extended dynamic range, and translucent mids and highs. Their soundstage was wide and deep, with surprising spatial resolution of different instruments or voices in a chorus. Jerome Harris' Taylor acoustic bass guitar and the kick drum in "The Mooche," from his Rendezvous CD (Stereophile STPH013-2), were placed directly in the center, Art Baron's trombone right of center, and Marty Ehrlich's alto sax far right. The 520i captured the shimmering bronze of Billy Drummond's Zildjian ride cymbal at the song's beginning, the plunger-muted trombone's brassy blattiness, and the crackle of the air in the mouthpiece of the sax. I was easily able to hear the call and response between trombone and sax.

The Radias accurately reproduced the spatial ambience of Robert Silverman's performance (via a large Bösendorfer reproducing piano) of the second movement of Beethoven's Piano Sonata 24, Op.78 (from his 10-CD set of the complete sonatas, OrpheumMasters KSP 830, engineered by John Atkinson), and the reediness and acoustic venue surrounding Antony Michaelson's clarinet in the Larghetto of Mozart's Clarinet Quintet in A, K.581, from Mosaic (CD, Stereophile STPH015-2). Listening to the excerpt from Elgar's The Dream of Gerontius on Test CD 2 (Stereophile STPH004-2), I was stunned by the width and depth of the soundstage: tenor far left, brass section far right, and the double choir set well back.

Well-recorded vocalists and instruments were what most benefited from the 520i's clarity and dynamics; they were reproduced with their timbres balanced and natural, free of speaker-introduced tonalities. Bud Shanks' virtuoso alto-sax and flute playing on the title track of the L.A. Four's Going Home (CD, East Wind 32JD-10043) had highs that were extended, open, and smooth. During "Silk Road" and "Running Water," from I Ching's Of the Marsh and the Moon (CD, Chesky WO144), I greatly enjoyed the timbres, sonorities, and resonances of Sisi Chen's Chinese dulcimer and Tao Chen's bamboo flute.

Dynamics were reproduced with incredible speed and an unusually wide range. The otherwise transparent and speedy Mark Levinson ML-2 monoblocks (50W RMS into 4 ohms) began to clip, so I switched to the more powerful Mark Levinson No.334 stereo amp (250Wpc RMS into 4 ohms) to get a better sense of the 520i's dynamic capabilities. Eva Cassidy, singing "Bridge Over Troubled Water" on Live at Blues Alley (CD, Blixstreet G2-10046), never sounded so good. The BG 520i conveyed the stunning dynamic range of her voice without ever overloading, honking, or running out of steam. I was also transfixed by the shimmer, sheen, timbre, and reediness of the reverberating chimes and the bassoon that open Owen Reed's La Fiesta Mexicana, on Fiesta (CD, Reference RR-38CD). However, the Revel Sub 30 was needed to hear the drama and power of the bass drum that opens this piece.

The subwoofer also enabled the Radias to span the dynamic range between drummer Mark Walker's tiny cymbal taps and the room-shaking kick-drum beats on "Nardis," from Patricia Barber's Café Blue (CD, Premonition/Blue Note 21810 2). Similarly, the Radias resolved the tangled but powerful syncopations underlying Brady Blade's explosive drum solo on "The Maker," from Emmylou Harris' Spyboy (CD, Eminent EM-25001-2). This live performance was resolved with stunning detail by the 520i: Harris' burned-out voice, the crowd noise and catcalls, Buddy Miller's lead electric 12-string and mando guitar, Blade's tight work on snare, bass pedals, and tom-toms. The Sub 30 also allowed me to enjoy deep organ-pedal passages with the Radias, particularly those in "Lord, Make Me an Instrument of Thy Peace" and "A Gaelic Blessing," from John Rutter's Requiem (CD, Reference RR-57CD).

The culmination of my listening experiences with the BG 520i was its dead-on portrayal of the complex orchestral timbres, instrumental placement, syncopated rhythms, driving pace, and wide dynamic range of Stravinsky's The Rite of Spring, performed by Eiji Oue and the Minnesota Symphony (CD, Reference RR-70). The 520i fully captured the eerie bassoon solo, played in an unusually high register, that opens the work. I heard and sensed the ballet's driving rhythms, magnified by the offbeat accents and the complex asymmetry of soft trumpets answered by cello pulses in the "Convocation of the Ancestors," where the roll of timpani is reinforced by the huge beat of a bass drum. The frenzy mounted further in the "Sacrificial Dance," where the speaker's superfast recovery allowed it to reproduce the sound of the musicians turning pages between timpani strokes! I found myself closing my eyes and tumbling into the music, so overpowering and involving was the experience.

Conclusions

The Bohlender-Graebener Corp. has achieved its goal of designing and manufacturing a tall, slim line-source loudspeaker with a small footprint that can compete with more expensive audiophile designs. The Radia 520i is faster, more dynamic, and better at imaging and involving the listener in the drama of music than it has a right to be at its price of $3998.

But doesn't it need a subwoofer to realize its full potential? While that's true, you might not miss a subwoofer if your musical tastes run more to singers than to pipe organs—I thought Eva Cassidy and Emmylou Harris sounded better when the Revel Sub 30 subwoofer wasn't playing. Many potential owners could start with the Radia 520is alone, then add a subwoofer if needed.

I was surprised to discover that the 520i put out enough bass for a range of different types of music. However, it couldn't repeal the laws of physics. When the music's bass demands increased, the 520i's woofers could strain and distort. Most often, the Radias provided clean, nonfatiguing sound, superb soundstaging that placed the instruments and voices with rock-solid stability, a wide dynamic range, and overall transparency. Add to all that its high build quality, moderate price, and ability to capture small musical details and instrumental timbres, and the Radia 520i earned my respect.

At $4000/pair, this loudspeaker is the best high-end value I've encountered in a long time, and its quality grew even more over the time I spent with it. Bohlender-Graebener Corp.'s Radia 520i gets my strongest recommendation.

Specifications

Description: Two-way, floorstanding, sealed-box loudspeaker with line-source ribbon upper-frequency driver. Drive-units: 50" by 1.1" planar-magnetic coaxial midrange and HF ribbon; two 6.5" cone woofers. Crossover frequency: 350Hz. Crossover slopes: fourth-order, Linkwitz-Riley. Frequency response: 70Hz-20kHz, ±6dB. Sensitivity: 88dB/2.83V/m. Nominal
Two-way, floorstanding, sealed-box loudspeaker with line-source ribbon upper-frequency driver. Drive-units: 50" by 1.1" planar-magnetic coaxial midrange and HF ribbon; two 6.5" cone woofers. Crossover frequency: 350Hz. Crossover slopes: fourth-order, Linkwitz-Riley. Frequency response: 70Hz-20kHz, ±6dB. Sensitivity: 88dB/2.83V/m. Nominal
Impedance: 4 ohms. Recommended amplification: 50-250W continuous, 300W peak.
4 ohms. Recommended amplification: 50-250W continuous, 300W peak.
Dimensions: 70.25" (1800mm) H by 7.75" (200mm) W by 2.75" (70mm) D. Base: 13.25" (340mm) W by 17.25" (442mm) D. Weight: 59 lbs (26.8kg).
70.25" (1800mm) H by 7.75" (200mm) W by 2.75" (70mm) D. Base: 13.25" (340mm) W by 17.25" (442mm) D. Weight: 59 lbs (26.8kg).
Finishes: Black anodized aluminum tower, black or mahogany base.
Black anodized aluminum tower, black or mahogany base.

Serial numbers of units reviewed: 02222, 02223.

Price: $3998/pair. Approximate number of dealers: 125.
$3998/pair. Approximate number of dealers: 125.
Manufacturer: Bohlender-Graebener Corp., 1780 Forrest Way, Carson City, NV 89706. Tel: (888) 875-2627, (775) 884-1800. Fax: (775) 884-1276. Web: www.bgcorp.com.
Bohlender-Graebener Corp., 1780 Forrest Way, Carson City, NV 89706. Tel: (888) 875-2627, (775) 884-1800. Fax: (775) 884-1276. Web: www.bgcorp.com.

Analog source: Linn Sondek-Lingo turntable, Linn Ittok tonearm, Spectral moving-coil cartridge.

Digital sources: Krell KRC-28 CD player, Sony SCD-C555ES multichannel SACD/CD player.

FM tuners: Day-Sequerra Classic, McIntosh MR-78, Sony ST-5000.

Preamplification: Mark Levinson ML-7 preamplifier with L3A MC phono cards, Margulis phono section, Duntech MX-10 head amplifier, Krell KCT preamplifier.

Power amplifiers: Mark Levinson ML-2 monoblocks and No.334 stereo amp; Krell FPB 600c.

Loudspeakers: Quad ESL-989, Revel Ultima Sub 30 subwoofer.

Cables: Interconnect: Red Rose Silver Ones, Krell CAST, Levinson Silver single-ended, Bryston balanced. Speaker: Mark Levinson HFC 10, Pure Silver Cable (PSC) R50 biwire double ribbon, Ultralink Excelsior 6N OFHC, Coincident Speaker Technology CST 1.—Larry Greenhill

Sidebar 3: Measurements

Ribbon speakers have historically offered low voltage sensitivity, but my estimate of the Bohlender-Graebener Radia 520i's sensitivity came in at 87.5dB(B)/2.83V/m, which is about average. However, its impedance lies at 4 ohms or below for much of the audioband, reaching a minimum value of 2.9 ohms at 165Hz. In addition, the combination of 4.2 ohms and -50 degrees capacitive phase angle at 120Hz, a frequency where music tends to have high energy levels, will stress lesser amplifiers. The impedance graph is free from the small wrinkles that would imply the existence of mid-frequency cabinet resonances. I couldn't get my accelerometer to stick to the rough black finish of the Radia 520i's small woofer enclosure, but it seemed inert to the knuckle-rap test. The small panel dimensions also mean that there is very little surface area to couple panel vibrations to the air.

The single bass peak at 80Hz in the impedance magnitude trace suggests that this is the tuning frequency of the woofers' sealed enclosure. This peak usually coincides with a speaker's -6dB point, which would suggest that the BG 520i offers only limited low-frequency extension. This is confirmed by the individual responses of the woofers and ribbon unit. (Both curves are a combination of the farfield response above 450Hz spliced to the nearfield response below that frequency.) The nearfield measurement technique boosts the apparent level of the upper bass, but even so, the 520i's bass rolls off below 120Hz or so. In-room, the fact that the woofers are placed close to the floor will give some useful reinforcement in the mid- and upper bass.

The ribbon unit appears to take over above 400Hz, but its output is marred by roughly equal dips and peaks up to about 15kHz, above which it rolls off steeply. The microphone was placed 50" away from the speaker on an axis level with the midpoint of the 50" drive-unit, and this may well not have been far enough away to properly characterize the behavior of a drive-unit as long as the Radia's ribbon. Even so, the unevenness of the measured response was consistent, and can also be seen in the Radia's response averaged across a 30 degrees horizontal window on the same axis. This graph also shows a slight lack of lower-midrange integration between the two drive-units.

BG Radia 520i, anechoic response on the center-of-ribbon axis at 50", averaged across 30 degrees horizontal window and corrected for microphone response, with the complex sum of the nearfield woofer and ribbon responses, taking into account acoustic phase and distance from the nominal farfield point, plotted below 300Hz.

The ribbon driver has fairly wide horizontal dispersion, but this is somewhat uneven with frequency, there being a flare in the treble region where the on-axis response had a lack of energy. In rooms of small to medium size this might well result in a more smooth, even treble balance at the listening chair. But note the sharp drop in output as the microphone approaches 90 degrees off-axis, due to the ribbon's dipole behavior. In the vertical plane, the long ribbon acts as a line source, meaning that the balance changes very little with quite large changes in listening axis.

BG Radia 520i, lateral response family at 50", normalized to response on center-of-ribbon axis, from back to front: differences in response 90 degrees-5 degrees off-axis, reference response, differences in response 5 degrees-90 degrees off-axis.

BG Radia 520i, vertical response family at 50", normalized to response on center-of-ribbon axis, from back to front: differences in response 15 degrees-5 degrees above axis, reference response, differences in response 5 degrees-15 degrees below axis.

Turning to the time domain, the Radia 520i's impulse response has a fairly good, time-coherent shape, its tail overlaid with some high-frequency ringing and what might be a close-spaced second arrival. This is also apparent in the step response, where what would have been a good right-triangle shape is disturbed by the second arrival. Both drive-units are connected with the same positive polarity; the positive-going hump in fig.7 results from the tail of the ribbon's step coinciding with the slow rise of the woofers' step.

BG Radia 520i, impulse response on center-of-ribbon axis at 50" (5ms time window, 30kHz bandwidth).

BG Radia 520i, step response on center-of-ribbon axis at 50" (5ms time window, 30kHz bandwidth).

Finally, the Radia 520i's farfield cumulative spectral-decay, or waterfall, plot is not as clean as I would like to have seen, with some delayed energy apparent in the low treble, though this doesn't appear to be due to resonances per se.

BG Radia 520i, cumulative spectral-decay plot at 50" (0.15ms risetime).

Measuring physically large speakers is always to some extent an exercise in frustration, because the inherent assumption made when a speaker is measured—that the microphone is in the farfield—is no longer correct at all frequencies. It is possible, therefore, that some of the aberrations seen in the Radia 520i's measurements are exaggerated. In which case, the best way to judge the speaker is to listen to it. I note that Larry Greenhill ended up being very impressed by the sound of the Bohlender-Graebener. I will set up the Radia 520i speakers in my own room and report on their sound in a Follow-Up to appear in the January issue.—John Atkinson

John Atkinson wrote about the Radia 520i in January 2005 (Vol.28 No.1):

When I measured the Radia 520i loudspeaker for Larry Greenhill's review in the December issue (p.115), I was bothered by the apparent unevenness of the 50" ribbon unit's frequency response. This unit covers the region above 400Hz, and its output was marred by roughly equal dips and peaks up to about 15kHz, above which it rolled off steeply. The microphone was placed 50" away from the speaker on an axis level with the midpoint of the ribbon for the quasi-anechoic measurement, and, as I wrote, this may well not have been far enough away to properly characterize the drive-unit's behavior. (The inherent assumption when measuring a loudspeaker's response is that the microphone is much farther away than the longest dimension of the speaker. With a 6'-tall speaker such as the Radia, that condition cannot realistically be met.)

I therefore set the review samples up in my own listening room, both for a weekend of auditioning and to carry out a spatially averaged response of the speakers' output at the listening position. (I average 120 individual 1/3-octave response measurements for each speaker driven on its own in a grid 18" high and 36" wide centered on the position of my ears.)

The results are shown in fig.9. The blue trace is the quasi-anechoic farfield response published in the December review, taken with a calibrated DPA omnidirectional microphone and DRA Labs' MLSSA system. The peaks and dips mentioned earlier are readily apparent, though it should be noted that the energy excess at 125Hz is an artifact of the nearfield measurement technique used to generate the trace below 300Hz.

The red trace is the spatially averaged response in my room, which takes into consideration the reverberant field, which in turn depends on the speaker's radiation pattern. (I used an AudioControl SA3050A spectrum analyzer, with its own calibrated microphone, for this measurement.) As Dr. Greenhill found, the speaker's mid- and low-bass output is prematurely rolled off, though in a well-controlled manner. The 520i is thus a natural match for a subwoofer. The unevenness in the anechoic on-axis curve can also be seen to smooth out, and the in-room response actually meets commendably tight ±2dB limits from 125Hz to 7kHz. Above that frequency, the Radia 520i's output falls off rapidly, pretty much mapping the anechoic curve.

Listening to the Radias (footnote 1), I was impressed both by the superbly defined, stable stereo imaging and by the smoothness of the sound. Bass was missing in action, but this was offset by the fact that there was no sense that the audioband was being covered by disparate drive-units. The integration between the twin 6.5" cone woofers and the ribbon was very well implemented.

However, while the suppressed top octave was not an issue for much of the time with both classical recordings and the usual overcooked modern rock discs, the lack of "air" in the Radia 520i's balance did occasionally intrude on recordings with naturally balanced high frequencies, such as the chamber-music recordings on my Editor's Choice CD (Stereophile STPH016-2). More important, I was sometimes bothered by a narrow band of brightness. This was audible, for example, as an added edge to the sounds of the solo voices on last September's "Recording of the Month," the Nikolaus Harnoncourt/Concentus Musicus Wien performance of Mozart's Requiem (SACD, Deutsche Harmonia Mundi 82876 58705 2). This balance correlates with the presence-region dip and the slight excess of energy in the mid-treble in the in-room response, my ear latching on to the latter as brightness rather than on to the former as a lack of presence. The opposite could also happen: Eric Clapton's Me and Mr. Johnson (CD, Reprise 48423-2) sounded too polite (though it must be said that Mr. C. does sound asleep at the wheel for much of this set).

Larry Greenhill summed up the Bohlender-Graebener Radia 520i as providing "clean, nonfatiguing sound, superb soundstaging that placed the instruments and voices with rock-solid stability, a wide dynamic range, and overall transparency." I'd say he basically nailed it, though I would want more top-octave energy.—John Atkinson

Footnote 1: My system comprised Mark Levinson No.33H monoblocks driven directly by a dCS Elgar Plus D/A converter fed by a dCS Verdi/Purcell SACD/CD front-end clocked by a dCS Verona and connected with a 1m length of DH Labs AES/EBU cable, as well as with dCS's FireWire links. Speaker cables were 1m lengths of AudioQuest Kilimanjaro; interconnects were 5m lengths of balanced Madrigal CZ-Gel.—John Atkinson

Bohlender-Graebener Radia 520i, quasi-anechoic response averaged across a 30 degrees horizontal angle on the center-of-ribbon axis at 50" with the nearfield woofer response plotted below 300Hz (blue); spatially averaged, 1/3-octave response in JA's listening room (red).

Larry Greenhill

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