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EQUIPMENT REVIEW - Acoustic Zen Crescendo
interstage transformer. I tried both output stage
configurations and clearly preferred the sound of
the 845 as being more vivid harmonically, better
focused, and more dynamic. I experimented with
speaker toe-in angle and preferred to intersect the
tweeter axes in front of the listening seat in order
to obtain the widest sweet spot and soundstage
lateral extension.
While I usually leave any discussion of bass
performance toward the end of a review,
preferring to start with the midrange, there’s a
compelling reason to reverse that order in the
case of the Crescendo. To confess, it became
painfully obvious that I had been living in a state
of perpetual sin listening to bass reproduction all
of these years through bass-reflex loudspeakers.
The Crescendo made that crystal clear as it
recalibrated my expectations in the bass range.
The attack and decay of an impulsive input signal
such as a kettledrum strike is stretched in time
by a phase-inverter speaker because a resonator
takes time to build up and then decay the signal.
It’s a well-known psychoacoustical fact, and a
critical performance factor, that our ears interpret
transient signals primarily in the time domain. A
classic experiment involves reversing the signal’s
attack and decay by playing a transient backwards
in time. The result is total auditory confusion. As
a consequence, it’s fair to say that a bass-reflex
speaker reproduces an impulsive signal in slow
motion. It may not matter as much with organ
music, which lacks crisp attack and decay, but
as the Crescendo made clear, even when driven
by the M845SE, tympanic strikes on a properly
loaded transmission line are peerless in terms
of control and definition. What the Crescendo
lacked in ultimate bass extension it made up for
with superlative time-domain performance.
The transition from the bass to the midrange was
seamless and without any audible discontinuity.
The Crescendo maintained realistic tonal weight
while doing justice to the power range of an
orchestra. In these respects it performed with
greater conviction than the similarly priced
MartinLogan Summit X electrostatic hybrid, which
tends to sound leaner through the upper bass.
Of course, the Crescendo lacked the midrange
transparency and textural delicacy of the Summit
X, but it wasn’t that far behind. It was also adept
at re-creating a persuasive spatial impression
with excellent depth, width, and nicely focused
image outlines. However, my personal preference
is for a dipole midrange, which I find, at least in
my listening room, to provide an enhanced spatial
impression and a more immersive you-are-there
experience.
In speaker land, what separates the men
from the boys is typically how well a tweeter is
integrated with a mid or woofer. It’s often not so
much about the choice of tweeter as it is about
selection of an optimal crossover frequency
and a sufficiently steep high-pass network to
adequately protect a tweeter from over-excursion.
For me the sonic kiss of death is a tweeter whose
distortion spectrum rises with signal level. In
my many years of audio reviewing, I’ve endured
so many ruthless-sounding tweeters that I’ve
developed an extreme sensitivity, an allergic
reaction if you will, to any upper-midrange and
treble harshness, grit, or gratuitous brightness.
I’m happy to report that the Crescendo’s ribbon
tweeter is a winner, capable of reproducing sweet
and refined harmonic textures with convincing
transient finesse. Its level of purity gives full scope
to violin overtones and female voice even when
driven to loud playback levels. The treble is so
well integrated with the corpus of the midrange
that I found it hard to believe that it was actually
crossed over in the upper midrange around 2kHz.
The overall tonal balance was quite neutral
sounding, and did not display an inherent bias.
Of course, the balance could easily be tilted
toward midrange warmth by a tube front end or
overly tubey power amp. But to its credit, this is
a speaker that allows the end user to make those
sorts of editorial decisions. The Crescendo was
just as comfortable with solid-state amplification,
though it was at its microdynamic best, able
to plumb the emotional depth of a recording,
when partnered by the M845SE monoblocks.
However, the macrodynamic range was best
served by a higher-power amplifier such as the
Bob Carver Cherry 180. This was a partnership
that made it possible for the Crescendo to live
up to its name. Orchestral crescendi were scaled
effortlessly without compression or distortion.
In fact, the Crescendo brought out the best in
the Cherry 180. The resultant soundstage was
transparent, dimensional, and bubbling with
kinetic energy—the essential ingredients for a
goosebump-producing experience. It’s fair to
say that the Carver amplifier with its pentodeconnected
output stage and a 1.7-ohm source
impedance benefitted from the Crescendo’s
uniform impedance magnitude and associated
linear phase. Pentode amps in general welcome
a resistive load, but unfortunately most real-world
loads are inductive and/or capacitive in nature.
As a consequence, pentode amps are difficult to
match successfully. The Crescendo comes about
as close to being an ideal resistive load as one
can expect from a box speaker. It’s the sort of
dream load every pentode amp would appreciate.
Acoustic Zen’s Robert Lee has crafted a
magnificent transmission-line speaker, truly a
perfectionist labor of love. The Crescendo is
eminently musical and supremely well-integrated
from top to bottom. It certainly pushed of all my
emotional buttons and is currently my favorite box
speaker under $30k. Make no mistake about it:
The Crescendo is a fantastic value at its asking
price. An enthusiastic five-star recommendation!
77 Guide to High-Performance Loudspeakers www.theabsolutesound.com
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