Sonus Faber Cremona loudspeaker Sam Tellig part 2
From Franco's point of view, my visit may not have been well-timed. He was busy voicing the Cremona, working closely and intensely with Lars Goller, development manager of Vifa-ScanSpeak, of Denmark. From my point of view, however, Lars's presence couldn't have been better. I not only got a sneak preview of the Cremona, I also got to witness an afternoon's listening and design session. Franco asked me to keep the Cremona a secret. And not to judge.
"It's not finished yet," he admonished. It took him another six months to tune every aspect of the drivers and the crossovers. "You know, Sam, if you change the value of just one resistor, you can change the sound entirely," he said at the time.
This is hard work. By day's end, Franco and Lars were clearly exhausted.
Working with Lars and the engineering team at Vifa-ScanSpeak, Franco requested a series of modifications to be made to the drive-units. Different generations of the drivers were compared—always with music rather than measurements as the guide.
To be sure, Franco uses computers to measure speaker performance. He also uses computers for quality control—to measure each speaker that comes off the production line, as I saw for myself at the factory. And ScanSpeak uses computers in designing their drivers.
But computers and software don't drive Franco's decisions. His ear, his experience, and his intuition do. While speakers today, on the whole, are better than ever, and while there's much more consistency than in the past, it seems to me that there is a certain sameness about many loudspeakers today, combined with something approaching sterility.
Should a speaker be entirely neutral? Should it be a transducer—something that passes the signal and just gets out of the way? Is accuracy everything? Or is a loudspeaker something more? Is it a musical instrument?
I asked Franco if he'd ever considered making his own speaker drivers. He shook his head. Franco likes the freedom to choose among drivers from all manufacturers of what he calls the "Danish School": Vifa, ScanSpeak, Peerless, Seas, Dynaudio. Danes have a way with drivers, just as Italians have a way with cabinets.
"Are the Cremona's drivers custom-made?"
"Customized, certainly. But each driver is based on an already-established unit. In the past, I was interested in having totally new drive-units designed. But now, with experience, I realize that that isn't such a good idea, because it is so difficult to design a good driver.
"Each manufacturer of drive-units has models which are superior. I choose from the market the best that is available and spend time adjusting the crossover and making whatever modifications are necessary."
I remembered something Franco had told me during my factory visit to Vicenza. He had a speaker that used a certain bass-midrange driver and wanted to make a larger speaker. (He didn't specify which model, but it might have been the Minima FM2.) He asked the driver manufacturer for a larger version based on the same design principles—but anything larger lacked the magic of the original driver.
A mass-market speaker manufacturer might not care. He might simply take the larger driver and use it to make a speaker, filling out a product line or meeting a price point. In other words, marketing considerations rather than musical considerations drive the design. If you want to know why so many speakers are ho-hum—not bad, not great—this is one of the reasons. If you want to know why some speakers in a manufacturer's line might be standout performers and others mediocre, well, here you have it.
The Cremona's drive-units all come from ScanSpeak, and I can attest that Lars Goller and his team worked really hard to give Franco just what he wanted. The 1" fabric-dome tweeter employs a "ring radiator" design. A metal phase plug sits in the center, surrounded by a ring of fabric into which is tucked the voice-coil former.
I asked John Hunter, of Sumiko Audio, Sonus Faber's US distributor, to elaborate:
"The [ring radiator] extends out to approximately 42kHz, and only the outer ring, or donut, emits sound. The approach brings two benefits. First, you reduce the moving mass, resulting in that fabulous high-frequency extension and air. Second, you improve the dispersion, especially lateral. Because of the neodymium magnet, the tweeter is highly sensitive and can play very loud."
I quizzed John about the crossovers. Specs are sparse with Sonus Faber designs.
"The tweeter is gently phased out starting at about 5-6kHz and is down 3dB at 3kHz," said John, after checking with Franco. "The woofer begins gently rolling off slightly below 100Hz and is 3dB down at about 300Hz. As with all of Franco's recent designs, the crossovers are first-order, with phase optimization involving minor corrective circuitry placed in parallel with the drivers. In this way, the fewest number of additional components are placed in series.
"Essentially, for all the tonic that the human voice and most instruments produce, you are listening to that single 5" midrange driver. The tweeter replicates the upper-level harmonics, while the twin 6" bass drivers act almost like subwoofers."
The cones of the midrange and bass drivers are made from "hand-thrown" paper, John added, knowing that would pique my interest.
"The paper isn't plain paper," he explained. "Various high-tech materials are been mixed into the pulp fiber—materials like carbon fiber and titanium dust." ScanSpeak and Sonus Faber do not supply a list of ingredients.
"When you hand-throw paper, that's what you do. You have a perforated screen that's maybe 4' by 8'. You throw the pulp fiber at the screen, it sticks, you let it dry for a while, then you throw some more, in fairly random form. You keep doing this over the course of two or three days, letting each layer dry."
"Sounds like fun."
"No, it's hard work, and takes considerable skill. At the end of three or four days, you have maybe 40 or 50 layers built up. The material is incredibly rigid, random, and internally self-quieting. You don't have common-mode resonances building up."
"What are those lacerations I see on the cones?"
"They're razor cuts applied to the cone at oblique angles."
"Why would you slash a speaker cone with a razor?"
"After hand-throwing the paper, you still have some vibrational standing waves emanating in a radial fashion from the voice-coil toward the rim, much like the waves rippling outward from a pebble dropped into a calm pool of water. These standing waves form a dominant sonic 'signature' in untreated drivers.
"So what they do at the factory is take a razor and actually slash the cone at oblique angles to the center. This breaks up the surface tension of the cone membrane. Any axial resonance runs into one of these razor cuts and is broken up. You can think of these razor cuts as an acoustical breakwater."
A polymer adhesive is then applied to heal the wounds, as it were, and keep the cone from shredding. The adhesive is said to be stronger than the cone material itself.
My review pair of Cremonas finally arrived—more than a year after my visit to Vicenza, and a few weeks before last fall's TOP Audio/Video show. I was going to set up the Cremonas in my cluttered upstairs living room—but when I saw them, I knew I'd have to listen in our living room. When my wife, Marina, came home, she flipped. Wife Acceptance Factor: 100%.
Our living room measures about 13' by 21'. I set up the speakers about 4' from the back, short wall and just under 3' from the side walls—my usual position for speakers in that room.