AXPONA 2012 Show Report -- Audio Expo North America
Warm winter brings cool sounds to the South
Show Coverage By A. Colin Flood

 

  The show held two special treats this year. I listened and talked with both the audio industry legend, Bob Carver, he of Phase Linear and Sunfire fame, and Prudence (Farrow) Bruns, she of the Beatles' "white" album fame.

 

The Legend Speaks
In a seminar with about four dozen people, Bob Carver talked about his new tube amplifiers and line driver arrays. A man much smaller and balder than his towering legend would have you image, this giant of industry made a lot of common sense, although his reasons might not seem so practical at first. He started by saying that a small tweeter can't reproduce the power of a oompapa band. One small tweeter per loudspeaker can't accurately reproduce overall rich sonic presentation (fast attacks in a broad spectrum of sound) of an oompapa band. Turns out, oompapa is a word in the musical vernacular. It means the rhythmical sound of a deep brass instrument in a band, a form of background ostinato. An ostinato (derived Italian "stubborn") is a persistently repeated motif or phrase. The oom-pah sound is usually made by the tuba, the pah is played on the off-beats by higher-pitched instruments such as the clarinet, accordion or trombone. Oompah is often associated with polka and waltz.

Sexy, Thin and Tall
Anyway, a small tweeter, he said, can't produce more than about one acoustic watt without distortion. His new 7' 4" arrays have eleven 4" high-excursion cones facing out each side and a line of 13 ribbon tweeters down the front, for a total of 35 transducers! Carver wants the loudspeakers to be extra tall in order to create an infinite height sound stage. Imagine, he told the audience, if each tweeter was a candle in a line candle array. Now imagine that array between polished mirrors on the floor and the ceiling above it. The reflections would be as bright as the original candles. Ideally, his thin towers would be located in a room with typical eight or nine-foot ceilings so the array and the reflections create the largest possible image.

Carver said he always liked ribbons since the famous Apogee loudspeakers impress him so much. His loudspeakers should be about 40 Hz to 40 kHz and cross over at high 800 Hz. The crossover will function like a first order one. Carver expects about 96dB/W/m efficiency. A frequency response greater than 20 kHz helps that lock images into place.

The demo room included a flat Sunfire Subrosa sub along the front wall. It had dual 10" hi-back EMF drivers powered by a 2700-watt tracking down converter amplifier made famous by Carver while he was at Sunfire. A sub-woofer adds impact and majesty, which he designed to be as flat as possible. He "loves lots of power." The bass amplifier provides 2000-watts and the arrays can handle 2600-watts per side. Using multiple drivers increases not only sound pressure levels, but also efficiency. The current prototype at the show was bi-amped with had four amplifiers, with 600 1200-watts per side. Using multiple drivers increases not only sound pressure levels, but also efficiency. The current prototype at the show had four amplifiers, with 1200-watts per side.

 

Why Tubes?
Why did the man famous for making one of the most powerful solid-state amplifiers in the '70s (350-watts), want to make tube amplifiers during his comeback? First, Carver said he had a love affair with tubes ever since he was little. He saw his own voice on an oscilloscope and was hooked! Second, music sounds nicer. Third, he said, Harry Pearson' articles, taught audiophiles how to appreciate products that provide realistic and deep acoustic space. Well, tube amplifiers can listen to the environment; the speakers are in much better than solid-state amplifiers. The loudspeaker acts like a microphone to provide feedback to the amplifier. Bob's amplifier uses all the information associated with the acoustics of the room. In his system, the signature of the room is fed into the amplifier which incorporates both current and voltage feedback loops.

Next, the output impedance of a tube amplifier is not zero. It follows the impedance characteristics of the driver. Music doesn't have to be flat to sound good. "A flat curtain of sound," Carver said, "means the beautiful space collapses." The facsimile reproduction, because a real one is not possible, only makes "something that could have existed in time and place." This is deep stuff here – when you think about it. According to Carver, the facsimile reproduction is more enjoyable than the flat curtain of sound that many amplifiers provide.

Confirming what Peter van Willenswaard reported in "Tubes Do Something Special," Carver said tubes watts are indeed more powerful than solid-state ones. The man in the audience said he heard twice as much, but Willenswaard found that tubes provide about five times more power than their rated watts. Carver's new amplifiers will use KT-88s and the new KT-120 tubes, which he said are KT-88s at twice the power. The new Black Beauty monoblock model sports three sets of KT-120 tubes for 305-watts into 8 Ohms and 290 into two. The Cherry red model uses KT-88 tubes for 200-watts into 8 Ohms and 215 into two. Both have a feedback control switch for classical (vintage tube) or contemporary (more modern) sonic signatures and output tube tester. The renown Dick Olsher is right now reviewing the new Cherry 180 models for Enjoy the Music.com. So check back for his review coming soon!

Also planned for his new loudspeaker system is an active crossover utilizing tubes. In the demo system was a Purity Audio tube pre-amplifier. The slaphappy room had no acoustic treatments other than a few orchids. Carver did however, deploy four graphic equalizers tailored to the driver set. On Patricia Barber's "Café Blue," the huge soundstage easily recreated a facsimile of her bar scene "that could have existed in time and place."

After listening first to Carver about audio engineering and then to Prudence about her life engineering experiences with the Beatles, meditation and yoga, it would have been appropriate to spend the rest of AXPONA listening to the Beatle's "white" album on Carver's new system. Alas, I did not. Perhaps I will save that for my own comeback. Already looking forward to AXPONA 2013!

This year, the show was exceptional for several reasons! Of course, it is thrilling to see such incredible looking, sounding and expensive systems. I also enjoyed the company of tweaking audiophiles on the drive there, at a room party, in a question and answer session with other writers and at dinner. Members of my audiophile club (Tampa) gathered in the hallways, at breakfast and dinner to compare notes; nothing like having a bunch of mostly middle-age techno geeks to share one's love of movies, music and home reproduction systems.

 

Audiowood
My friend Joel Scilley did not have a vendor room at AXPONA this year. He crafts quality components into award winning wood designs. His popular Barky turntable features a round slab of wood, Rega arm and cartridge. Magazines like Metropolitan Home and California Home and Design love his work. Scilley showed off a prototype solid wood loudspeaker. He also hosted a room party for my Meetup.com group.  

 

 

Click here for next page.