ADAM Audio Classic Column MK3 loudspeaker
ADAM's ribbon drivers are based on Oskar Heil's original Air Motion Transformer. The AMT was popular in the early 1970s, principally for its use as the tweeter in the AMT-1 loudspeaker, designed by ElectroStatic Sound Systems. Fundamentally, the AMT is a relatively long ribbon in which is embedded a serpentine aluminum strip that functions as a voice-coil. The strip is then folded, accordion-style, and suspended in a strong dipole magnetic field. When the signal current is passed through the aluminum strip, the alternating, now-adjacent portions of the strip attract and repel each other. The result is a rapid opening and closing of the accordion pleats that effects a rapid expiration and inspiration of air between them.
According to Heil, this accelerates the air five times faster than could a diaphragm radiator, and contributes to the AMT's wide dynamic range. It has relatively high power handling because the actual area of the voice-coil and ribbon is many times larger than the area that faces the listener, due to the folding, and because the soft ribbon material is relatively nonresonant. The popularity of the commercial speaker resulted in the publication of many DIY articles based on it; I built a pair of AMT speakers based on a design published in Audio Amateur in 1977. New AMT-based commercial and DIY designs still appear today.
Physicist Klaus Heinz, who met Oskar Heil in 1982, says on ADAM's website that he thought that "the new kinematics to move the air was intellectually brilliant, and the audible success inspiring." Heinz and electrical engineer Roland Stenz founded ADAM Audio in Berlin, Germany, in 1999, and remain committed to the further development of the AMT principle. This has resulted in ADAM's eXtended Accelerating Ribbon Technology (X-ART), which eliminates "huge magnetic structures in front of the diaphragm," thereby removing some of the horn-like coloration of the original design and permitting wider dispersion. The use of modern materials, such as Kapton diaphragms and neodymium magnets, reduces distortion and improves sensitivity, dispersion, and power handling. These improvements have also made possible the manufacture of midrange X-ART drivers.
The subject of this review, the Classic Column MK3, uses a small X-ART driver from 2.8kHz up, and a larger X-ART driver from 2.8kHz down to 800Hz.
Meanwhile, back in the States, years passed. At each subsequent CEDIA Expo or Consumer Electronics Show, ADAM's Roger Fortier and I kibitzed and reaffirmed that I really should write something for Stereophile about ADAM Audio. Recently, I visited a Manhattan audio shop and, lo and behold, there in the main listening room were ADAM Tensor Betas (ca $30,000/pair in semi-active form) and, in another room, the passive Classic Column MK3s. Both sounded exciting enough to get my juices flowing and overcome my long inertia. I chose the passive Classic Column because it's attractively priced at $7000/pair, and because I think most Stereophile readers prefer to use their own amps. There is also an active version ($10,000/pair) that may well be the subject for future investigation.
When Roger Fortier delivered the Classic Column MK3s, I realized I'd chosen wisely. It's a clean, beautifully simple design with smartly chamfered edges, four drivers on the front, two ports on the back, and two pairs of multiway terminals for single or biwiring. The drivers are vertically arrayed: tweeter and midrange ribbons above, the two woofers below.
Those woofers have HexaCone diaphragmshoneycomb Nomex structures coated with Kevlarand are individually loaded inside the cabinet, each with its own port. ADAM states that the Classic Column is a 3.5-way speaker, which is confirmed by the inclusion of a 150Hz crossover specification, both woofers operating together below that frequency. The lower woofer rolls off above 150Hz, leaving the upper woofer to provide a better blend with the midrange in terms of dispersion.
The Classic Column is supported by a stiff, heavy base, to which are affixed adjustable and imposing spike feet. The grille is magnetically attached; those of us who tend to eschew grilles can have a front panel unmarked by unused fasteners. All in all, an impressively executed design.
Fortier and I placed the Columns in the spots where similar speakers had worked so well in the past, hooked them up to the system, and let 'em rip. My first impression was distinctly positive. There was no doubt that the Column was a well-balanced, full-range speakerexactly what I'd been led to expect from what I'd heard in my previous encounters with them. On axis, there was no significant difference between the sounds, grilles on and grilles off, but the soundstage's width and, to a smaller degree, its depth seemed a bit limited with them on. This precipitated a series of adjustments of position, toe-in angle, and grilles on/off. The optimal combination seemed to be: speakers toed in so that their tweeter axes crossed 12' behind the listening position More acute toe-in angles increased the soundstage width a bit at the expense of depth; less acute angles produced the opposite effect. I reached the same conclusion as before about the grilles, and the same preference: leave 'em off.