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Product Review - Bohlender-Graebener Radia X3 Ribbon-Hybrid Floor-Standing Speakers - August, 2001

John E. Johnson, Jr.


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Specifications:

Drivers: One 3" Ribbon Tweeter, One 5 1/2" Aluminum Cone Mid-Range/Woofer, One  5 1/2" Aluminum Cone Woofer

MFR: 40 Hz - 30 kHz

Nominal Impedance: 4 Ohms

Power Handling: 150 Watts

Sensitivity: 93 dB/2.83 Volt/1 Meter

Size: 40" H x 7 3/4" W x 9 1/2" D

Weight: 35 Pounds Each

MSRP: $2,050/Pair USA

 

 

Bohlender-Graebener Corporation, 1780 Forrest Way, Carson City, Nevada 89706-0311; Phone 775-884-1900; Fax 775-884-1276; E-Mail sales@bgcorp.com; Web http://www.bgcorp.com/home.html

Introduction

Bohlender-Graebener is a small speaker manufacturer in an area of Carson City, Nevada with streets like Boeing Way, Convair Drive, and Lockheed Way, so you can imagine the kind of high technology there. They specialize in planar-magnetic drivers, using ribbons, and have developed a proprietary technology for getting the tension of the ribbons just right.

Many of their products use full length ribbons, but they also make some with small ribbons and cone drivers (hybrids) like the new X3 under review here. The Radia series includes models that are for in-wall situations. The X3s are sold only on the Internet at this time. Places like UBid are getting the them to consumers at less than $1,000 per pair, which makes them a bargain. The Internet is turning out to be one heck of a place to buy really affordable hi-fi equipment, and the choices are only going to get better and better over time.

A ribbon driver consists of a thin metal foil (the ribbon) suspended between powerful permanent magnets. In the case of the X3s, the ribbon is metal etched onto a Kaladex plastic film (Kaladex is made by Dupont), and is considered to be a planar-magnetic driver. The audio signal is applied to each end of the ribbon, and the current flowing through the ribbon creates an electromagnetic field that is attracted and repelled by the permanent magnets. Since the ribbons are much lighter than conventional driver cones, they have extraordinary speed and accuracy. They can even reproduce square wave signals. They are considered a line-source rather than a point-source driver.

The X3s

The X3 is a hybrid three-way design, using a 3" ribbon as the tweeter, a 5 1/2" aluminum cone driver for the midrange/bass, and a 5 1/2" aluminum cone driver as the woofer. Both of the bass drivers have phase plugs. Crossover is at 2.4 kHz to the tweeter and 500 Hz to the woofer. They have a very nice set of gold-plated speaker binding posts (bi-ampable), and are ported just above the binding posts.

Igor Levitsky, BG's engineer, told me, "The two woofers work from the lowest frequency until 500 Hz, then the lower woofer starts rolling off. Thus, the X3 has one (the upper) mid-woofer which is closer to the tweeter, working up to 2.4 kHz where it crosses over to tweeter. Having only one woofer working in the upper midrange band allows better dispersion, better imaging, more balanced reproduction, and seamless vertical integration. Also, 500 Hz is very close to a "baffle" diffraction step that increases output of any system. This technique compensates for the diffraction effect as well. The 500 Hz rolloff is a first order network. The 2.4 kHz crossover between the upper mid-woofer and the tweeter is a second order Linkwitz-Riley network that sums at -6 dB in phase, thus yielding a flat frequency response. From my experience this works the best in all respects. Thus, the X3 crossover provides seamless integration, does not produce excessive lobing, does not present a hard load for amplifiers, and provides reliable system operation protecting the tweeter from excessive mid frequency peaks. All inductors are air core for perfect linearity. All capacitors are polypropylene for minimum distortion and high resolution."

The finish is cherry vinyl, and they have a modern black acoustically transparent polycomposite grille with anodized aluminum trim along the front, and which are very stiff so as to help prevent cabinet resonance. The baffle is rounded to reduce the effects of diffraction (interference between the sound coming from the driver itself and sound that is reflected from the baffle). Metal grilles are becoming quite vogue these days, and they are much sturdier than cloth.

The Sound

I tested the X3s with an Audio Alchemy CD transport, Perpetual Technologies P-1A and P-3A, Balanced Audio Technology VK-5i preamplifier, Balanced Audio VK-75SE power amplifier, and Nordost cables. Music was a wide variety.

Although I am quite familiar with ribbons and ESLs, I had not reviewed speakers with a ribbon tweeter and conventional cones for the rest of the signal. So, frankly, I did not know what to expect. John Kotches has reviewed BG speakers, but this was my first experience with their products.

The enormous amount of detail was what hit me first. Astonishing in fact. For example, in Mozart's Piano Concerto in B Flat (Philips), I could hear the hammer pads, and when Eva Cassidy sang, I could hear her tongue clucking as she enunciated the consonants. It takes a very fast driver to do this.

Midrange was natural and full bodied without being mushy. This is one of the advantages of devoting a driver to the midrange, but three-way speakers are not easy to design. And neutrality in human voices, which are in the midrange bands, is critical. The X3 has that neutrality. Using an aluminum cone is a necessity with a design that has a ribbon tweeter, because otherwise, the mids would be sloppy compared to the speed of the highs. This is exemplified in John Williams' "Echoes of London" (CBS Records), where the rosin on the strings and the pick against the strings blended nicely with the actual notes that were being played.

With such a modest sized bass driver, I thought the X3s might be a little weak in the low frequencies, but that was not the case. Kettle drums in Rimsky-Korsakov's "Dance of the Tumblers" (Reference Recordings, Exotic Dances from the Opera) thundered, yet were very tight. That is not to say these speakers would handle all the deep bass if you ran them full tilt with a massive sound track. A good subwoofer is in order with all but the very largest of speakers, and the X3s are no exception. Something like a Velodyne HGS-10 or Sunfire subwoofer sitting behind the couch will take care of that problem good and proper, which is what it did here. With Mussorgsky's "Pictures at an Exhibition" transcribed by Jean Gillou (Dorian Records) for pipe organ, those big pedal tones needed the sub for that last low octave (20 Hz - 40 Hz).

Conclusion

The X3s are simply delightful speakers. Their modern looks will fit into any decor, with their slender design and black metal grille. The sound is clear, neutral, clean, and tight. The ribbon tweeter distinguishes their tonal quality with high speed. Add a little subwoofer and you will be in audio nirvana.

 

- John E. Johnson, Jr. - 

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Copyright 2001 Secrets of Home Theater & High Fidelity
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