Recording - March 2017 - 48

you don't get the little phase cancellations and reinforcements
that can occur when two separate speakers' sounds reach your
ears at different times. This offers a wider sweet spot; moving
your head doesn't affect the monitor's timbre as much.
On most coaxial speakers made to date, the tweeter is a dome
design; they're compact, so they're easy to place atop the woofer's voice coil, with or without a waveguide surround for more
uniform distribution. The FPX7, however, uses an AMT (Air Motion Transformer), a design originally developed by Dr. Oskar
Heil and popularized on a variety of speaker lines. Many engineers prefer the sound of an AMT tweeter; it's made from a long
flat ribbon of plastic that's gently folded into an accordion pleat,
which opens and closes in a manner much like the human voice
box. This design has a very fast transient response and moves a
lot of air from a very small space, giving a very extended and
sweet-sounding high end.

Front and rear

PRICE: $549.99 each
MORE FROM: Fluid Audio, www.fluidaudio.net

Fluid Audio
FPX7

Two technologies combine
in a truly unique monitor

REVIEW BY MIKE METLAY

W

e first introduced readers to speaker designer Kevin
Zuccaro and his firm Fluid Audio in our November
2016 issue, where we gave a glowing review to the
FX8 coaxial monitor, which we believe is an exceptional value for
the money. That review period was also the beginning of our look at
the new FPX7, an unusual (to say the least) monitor design that combines coaxial speaker design with an AMT "folded ribbon" tweeter.

Understanding the tech

A coaxial monitor is designed with one driver placed inside
another. In a 2-way speaker like the FPX7, the tweeter's inside
the woofer; in a 3-way speaker, the tweeter's inside the midrange
driver. Why do this? Centering one driver inside the other causes
the sound from each speaker to come from the same point in
space and time; phase is coherent between the two. As a result,
48

RECORDING MARCH 2017

The FPX7 combines these two design elements with a 7"
composite-paper woofer and a 3" waveguide containing a 28
x 43 mm (1.1 x 1.7 inch) AMT tweeter. These are combined
in an elegantly-shaped and very compact enclosure, at 308 x
217 x 264 mm (12.1 x 8.5 x 10.5 inches) weighing 7.5 kg
(16.5 lb). The FPX7 has a 42 Hz-27 kHz frequency response
(±3 dB), 90 and 50 Watt amplifiers for woofer and tweeter,
and a 3.5 kHz crossover frequency.
The FP in the monitor's name stands for "Fader Pro", due to the
FPX7's front-fascia detented volume fader next to the backlit Fluid
Audio logo. With click-stops at 0 (full volume), -3/-6/-18 dB, and
muted, this fader allows for quick and accurate level calibration
between speakers, although once it's set up in your studio you're
unlikely to ever need to touch it again. The logo and fader are
above the drivers, and below them is a front-firing bass reflex port.
The rear panel of the FPX7 sports adjustments for tweeter
high-frequency trim (-2/0/+2 dB) and a highpass shelving
filter to control boundary effects (corner frequency 200 Hz,
-4/-2/0 dB). Inputs include balanced XLR and 1/4" TRS as
well as unbalanced RCA. Underneath the substantial rear-panel
heat sink is the IEC power connector and power switch.

First pass

Our initial listening sessions with the FPX7 left us scratching
our heads. There were significant frequency response anomalies
in the upper mids (right around the crossover frequency) that we
found bothersome, and-paradoxically for a coaxial monitor-a smaller-than-usual sweet spot, with audible tonal shifts
from moving more than a foot or so to either side. Our initial
guess was that this was due to the AMT being much bulkier
than a dome tweeter. Even though the FPX7's waveguide is
no wider than the FX8's, it's much deeper and more massive,
placing a big obstacle (and source of interference) in the audio
radiation pattern of the 7" woofer, which is already on the small
side. In addition, the AMT tweeter delivered a lot of treble; any HF
Trim setting other than -2 dB sounded overly bright.
We reached out to Fluid Audio and learned from Kevin
Zuccaro that a small number of early-release FPX7 units had
significant voicing issues, which had since been addressed. Kevin


http://www.fluidaudio.net

Table of Contents for the Digital Edition of Recording - March 2017

Contents
Recording - March 2017 - Intro
Recording - March 2017 - Cover1
Recording - March 2017 - Cover2
Recording - March 2017 - 1
Recording - March 2017 - 2
Recording - March 2017 - 3
Recording - March 2017 - 4
Recording - March 2017 - 5
Recording - March 2017 - Contents
Recording - March 2017 - 7
Recording - March 2017 - 8
Recording - March 2017 - 9
Recording - March 2017 - 10
Recording - March 2017 - 11
Recording - March 2017 - 12
Recording - March 2017 - 13
Recording - March 2017 - 14
Recording - March 2017 - 15
Recording - March 2017 - 16
Recording - March 2017 - 17
Recording - March 2017 - 18
Recording - March 2017 - 19
Recording - March 2017 - 20
Recording - March 2017 - 21
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Recording - March 2017 - 25
Recording - March 2017 - 26
Recording - March 2017 - 27
Recording - March 2017 - 28
Recording - March 2017 - 29
Recording - March 2017 - 30
Recording - March 2017 - 31
Recording - March 2017 - 32
Recording - March 2017 - 33
Recording - March 2017 - 34
Recording - March 2017 - 35
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Recording - March 2017 - Cover3
Recording - March 2017 - Cover4
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