Carver Amazing Loudspeaker (Platinum Edition) Page 4

There was lots of midrange and treble detail, and it was resolved clearly enough—commensurate with the performance level you'd expect from a fast transducer like a ribbon. So it was all the more disturbing to deal with the level of reproduction below 500Hz or so. On the one hand, you have lots of scintillating treble detail that beckons you to get involved in the music. On the other hand, the lower octaves serve to isolate you from the music. Taken as a whole, the midbass, upper bass, and lower midrange were veiled and muddy. Bass lines were consistently ill-defined and difficult to follow. Because much of a hall's sonic signature resides in this range, it was not surprising that I could not penetrate deep into the soundstage. I just could not get an adequate sense of hall. I could not place myself in the space of the performance.

Every one of my records that I've come to depend on for soundstaging evaluation, the Proprius Laudate! and Cantate Domino for example, failed to flesh out properly through the Amazing. I could make out the leading edge of hall reverb, but its trailing edge became indistinct. It was as though a thick curtain were dropped before my eyes at a crucial moment to obscure the true expansiveness of the hall. The loss of soundstage transparency and immediacy was so obtrusive and disturbing that I had to try something.

One of the things I tried was a number of amplifiers, including Carver's Silver Seven-t monoblocks. The Seven-t turned out to be a sonic disaster, combining the worst attributes of solid-state and tubes. Treble transients were sizzly and steely, the bass heavy and undifferentiated—sort of a bloated thump. The mids were dryish and grainy. And the soundstage—what a mess! Compressed depth to the point of one-dimensionality, and never really coalescing into a unified whole. And to think that Carver had wanted me to bi-wire the Amazing with no less than two pairs of the Seven-ts. The Krell KSA-200 provided the Amazing with a much-needed dose of bass control, but it also emphasized the ribbon's mechanical resonances. The Music Reference RM-9 offered much-needed midrange liquidity without exacerbating the presence-region nasties, but wasn't nearly as accomplished as the Krell in the bass.

The ideal amp for the Amazing (this is true for many ribbon-based designs) would be one that combined solid-state bass control and current drive with tube-like liquidity, textural softness, and imaging. I only wish money could buy such a beast.

In desperation, I decided to try one final trick: a cheap experiment, if you will, since it only involved a dollar's worth of masking tape. I experimented with taping the back side of the ribbon; ¾"-wide tape was just fine for this application, as it neatly fit over the slits in the magnet structure. The optimum pattern turned out to be one where alternating slits were taped shut. The idea was to try and resistively dampen whatever ribbon resonances I could. The really amazing thing was just how effective this idea turned out to be. The ribbon's inherent presence-region resonance around 5–6kHz was not abated, but the difference in the lower octaves was nothing short of dramatic. The upper-bass heaviness largely disappeared. Bass lines became distinct. And, just as important, soundstage transparency shot up to a point where I had no difficulty any longer in delineating hall size—as though the fog that had previously surrounded this region all of a sudden evaporated.

Another surprise was that the veiling was not caused by the woofer section, but rather by the ribbon's bass resonance. This dramatic change for the better is readily apparent from fig.A. (The curves were generated during Bob's subsequent visit to Santa Fe.) The top curve shows a peak of some 14dB centered at 150Hz for the undamped ribbon. With a swatch of silk applied to the back of the ribbon for air-flow resistance, the bottom curve shows the end result. About this time Bob Carver phoned me with a major announcement.

AmazfigA.jpg

Fig.A Carver Amazing Loudspeaker, nearfield ribbon response with (red) and without damping (blue) (10dB/vertical div.).

Act II
Here I am itching to close out this project, and Bob announces that the current Platinum version of the Amazing, the one I have been listening to, has been discontinued. According to Bob, there are new grilles for the front and back that reduce diffraction effects, as well as a new crossover network. I wonder about Bob's amazing timing, but naturally I want a new sample as soon as possible to close the loop. Bob has a better idea. Since my pair of Amazings was already broken in, why not come out to Santa Fe and install the various upgrades himself?

So, on a Saturday morning in October, there's Bob in my listening room, along with Mark Friedman (Carver's National Sales Manager) and John Atkinson. The grilles are here, but what about the crossover? Bob waves this Rube Goldberg contraption about that looks like an octopus in heat. It turned out later that this "new crossover" was thrown together by Bob that same morning in his motel room using Radio Shack parts and a coil-winder he brought with him. What Bob really wants to do is spend the day experimenting and hopefully end up with something Stereophile likes. We spend part of the morning listening; Bob really likes the concept of damping the ribbon. So we spend part of the afternoon scrounging for various damping-material samples, including nylon stockings, silk cloth, and chiffon. The results of the silk damping experiment (fig.A) are so impressive and Bob so ecstatic that he resolves to incorporate some form of damping in all future production.

Next Bob attempts to build a notch filter to counteract what he measures to be a 7kHz peak in the ribbon response. A new crossover is installed late that evening, and, after some additional listening late into the night, it's clear that the tonal balance still isn't quite right. As Bob leaves, I make it clear to him I expect a new production sample incorporating all of the final changes.

Act III
Sample 2 arrived at the end of October 1989. It differed from the first sample in several ways. First, damping was provided on the back side of the ribbon assembly. Bob decided to use a thin gauze-like material called "pre-wrap." This stuff was taped to the back of the baffle with electrical tape; a temporary measure, Bob assured me, until the proper moulding is fabricated to hold the gauze in place. Second, the crossover network was revised to better blend ribbon and woofer. The crossover frequency was pushed slightly higher to compensate for the 2dB loss in ribbon efficiency incurred by the damping material. A 7kHz notch filter was included in the network to kill a major ribbon resonance. A Very-High Frequency (VHF) control was added to give the user some control over frequencies above 10kHz. This, according to Bob, helps in controlling a treble resonance in the range of 10–12kHz. Third, new woofer grilles were installed with larger cutouts on the back side. Fourth, a "High-Altitude" resistor kit, with instructions, was included for adjusting the damping of the woofer section. Finally, this particular pair of Amazings was supposedly already broken-in by Bob prior to shipment.

This pair certainly sounded much smoother right out of the box, so much more so than our broken-in first sample that I began to suspect one of two possibilities: either this was a hand-selected sample unrepresentative of the lot, or just a randomly selected lucky sample. If the latter possibility is the correct one, it highlights QA problems in getting these ribbons to sound alike.

We proceeded to break in the second sample for an additional 50 hours. The first listening session with the new Amazing proved to be more of a positive experience than the first sample ever provided—although I still had some major reservations. Bass definition was decent, although still lacking much impact. There wasn't much sense of punch; bass attack was more like a limp noodle than a whiplike crisp. The amazing thing about the Amazing was that, despite measuring flat into the low 20s, its deep bass simply failed to sound that way. There was always lots of bass, but on organ recordings the Amazing could not generate a convincing bass foundation below about 40Hz.

The "High-Altitude" kit provided by Carver with the Amazing allows for the insertion of either a 1 or 2 ohm resistor in series with the woofer section. According to Carver, this is supposed to lower the woofer Q and thus tighten the bass. I would agree that a series resistor would reduce the quantity of bass, but I don't see how the Q of the response is lowered in this fashion. Substitution of the 1 ohm resistors per Carver's instructions is not straightforward: it forces you to bi-wire the speakers, but since that in itself is not a bad thing, it should not prove a deterrent. The resistors clearly reduced bass output. But, just as clearly, bass quality was not improved. In fact, the midbass got more muddled, taking on more of a one-note bass character. Charlie Haden's double bass on "Lonely Woman" on The Shape of Jazz To Come (Atlantic CD, 1317-2) not only became more anemic, but pitch definition decreased to the point where his lines were hopelessly muddled. This resistor kit is a miscalculation; my kind recommendation would be to give it a hasty burial.

However, the Amazing's imaging was much improved with these samples. Soundstage width and depth were both more than adequate, and the level of transparency through the lower mids and upper bass was quite astonishing when compared with the first sample. Hall reverb was now easy to resolve, and resolution of massed voices was very good. With both pots at their nominal 12 o'clock positions, the upper octaves were now quite listenable. Much of that presence-region scream was absent. The presentation was still overly sibilant, and treble transients were still a tad on the hot side—but tolerably so. The problematic upper mids remained very much so. Timbres through this region just didn't sound right. No combination of UMR and VHF pot settings managed to restore timbral accuracy. The best compromise turned out to be a 12 o'clock pot setting, but I was left with the impression that the Amazing was still hopelessly colored in this region.

A magical moment
At some point during the second session, something very magical happened. It was as though the sky opened up and a hand descended to bless the Amazing. I was diddling with the toe-in angle again, but that wasn't really it. All of a sudden the Amazing got smoother and sweeter at the top, and I found myself suddenly drawn into the music. For the first time, I found myself enjoying these speakers. Things weren't altogether right, but there was enough right here to combine for an enjoyable experience. The upper range of Lesley's voice was still adulterated. But the focus of her vocal outlines was tight, and midrange textures were smooth. An occasional squawk crept in around 1kHz in one of the ribbons. And you also need to know that the ribbon buzzes like a kazoo below 1kHz. The buzzing is normally not audible, being masked by the music. But with pure sinewave test signal it's easy to pick out the accompanying buzz.

But enough bad news for now—the Amazing was beginning to flex its muscles. Record after record was thrown on the Aura turntable (an excellent 'table from Down Under; review forthcoming), with very musical results. Pilar Lorengar as Princess Pamina (The Magic Flute, London OSA-1397) really shone with an intense vocal purity. Mezzo-soprano Janet Baker's voice (Holst: Savitri, Argo ZNF-6) was reproduced with a honey-smooth quality. The husky hue of Cleo Laine's lower registers (Live At Carnegie Hall, RCA LPL1-5015) was perfectly captured by the Amazing. Therese Juel's voice on the Opus 3 Test Record 1 was well-behaved—just slightly erring toward oversibilance. Violin tone was just as captivating. Itzhak Perlman grooves on this sort of music. The Bruch Violin Concerto (EMI ASD 2926) is just the sort of repertoire to give Itzhak freedom to ooze calories. That he does, and the Amazing reproduced his violin tone with sufficient sweetness and suaveness. High-powered orchestral material was reproduced with excellent dynamics. Retrieval of low-level detail was excellent, even when confronted with complex, dense musical passages.

Act IV
It's mid-November. You guessed it. Another phone call from Bob. He's changed the crossover again. As I write this, Bob may be on his way to Santa Fe to install the upgrade. If he does, I'll report the results in a future Follow-Up. And one more thing. Bob followed up on a suggestion of mine to treat the ribbon foil surface with a damping material. Bob used a 3M damping compound which he brushed onto the foil. He found that the treatment yielded, in his words, an instantly broken-in, or "aged," ribbon. The problem is that because of the increase in moving mass, the efficiency drops dramatically. So Bob is thinking of completely overhauling the ribbon design as a long-term project in order to bring the efficiency back up. In a year or so, there may very well emerge "Son of Amazing."

Taking stock
Coupling the Amazing's relatively modest asking price with the level of performance achieved by what has to be viewed as a transitional prototype, there looms the potential for a great speaker. At the outset it should be emphasized that, even at its best, the Amazing possessed an inescapable coloration in the presence region. With this speaker, you'll forever be married to an oversibilant presentation. You can hear the 5kHz peak as an emphasis of surface noise, and it also gives treble transients a slightly zippy or hot character.

On the positive side, the Amazing is capable of exquisite midrange textural smoothness and sumptuous liquidity. Low-level detail resolution is excellent: no nuance is too small for the Amazing. The dynamic range is excellent. The Amazing will play loud without audible compression or congestion. With the right amp, the lower mids take on a convincing authority. Bass extension is very good, with decent impact, but don't expect amazing bass quality and definition. The Amazing's bass performance is very amp-dependent, with a solid-state amp being a requisite for eliciting its full potential. The rub is that a typical solid-state amp is likely to exacerbate the Amazing's presence-region zip. With a lot of sweat and tears in setup, the soundstaging can be quite convincing, with excellent spatial resolution. The damped ribbon is sufficiently transparent to allow one to gaze very deeply into the soundstage and to clearly delineate hall size.

There's some buzzing and grille snapping on large bass transients, but generally I have not found these warts to be annoying because they're masked by the music.

Finally, the big question mark is variability in ribbon quality. Unquestionably, it takes the ribbon a long time to break in. In the interim, the sound is rough and edgy. The controlling factors here do not appear to have been adequately researched by Carver. JA expressed the opinion that Carver's method of clamping the ribbon may not be optimum. That I do not know. But I can tell you that waiting for the ribbon to break in is like having to go through puberty all over again: it's a royal pain in the butt. But when that magical day dawns, the Amazing begins to smile at you and all may be forgiven—unless you've lost your patience along the way.

Finally, I want to make it perfectly clear that, as of now, I do not recommend this speaker. If and when the design stabilizes, and I have a chance to evaluate a true production sample, then a final assessment can be rationally made. I consider it insane to spend any money on what has to be regarded, for now, as an evolving prototype.

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