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