Atohm GT 1.0 - Ultra High-End Audio and Home Theater Review

O N T E S T
Atohm GT 1.0
LOUDSPEAKERS
There’s no doubt that, like the Italians,
the French have flair. Or a
chic ‘je ne sais quoi’. Check out the
country’s main audio companies
(especially the loudspeaker manufacturers)
and you will find distinctive products
incorporating innovations and examples
of lateral thinking of a standard that would
make engineers from other parts of the planet
green with envy. Hand-crankable propagation-aligning
spinal rib-like enclosures à la
Focal’s Utopia? Spherical enclosures bearing
quad-axial drivers chez Cabasse? Ceilingreaching
stacked enclosures with exoticallydesigned
bullet-shaped tweeters per Triangle?
I could go on…
Atohm is another French speaker manufacturer,
and a relatively new one at that, but
one with a somewhat more conventional
penchant for beauty in design and sound.
Thierry Comte, who was formerly Technical
Director at Triangle, has decided to go
it alone and is now at the helm of Atohm,
designing products that reap the benefits
of his vast experience in loudspeaker
design and production. The subject at hand
is the entry stand-mount speaker in the
flagship GT range—the GT 1.0.
The Equipment
The GT 1.0 speakers come solidly triple-box
packed and double-bag protected. The ‘bag
inside a bag’ arrangement serves not only
to protect the stunning finish (more on that
later) but one of the sacks is soft enough to
serve as a polishing cloth. No matter how
pedantic you may be, as you un-bag the GT
1.0, you won’t fail to be impressed by the
build quality and overall fit and finish of the
cabinetry.
Also in the box—and most unusually—
you will find that Atohm actually provides
a choice of two baffle grilles. Both attach via
embedded magnets with the full-sized bulletshaped
grille just about covering the speakers’
fascia while opting only for the smaller circular
one provides protection for the 153mm
mid/woofer (that’s it’s overall diameter, the
Thiele/Small diameter is 114mm, for an Sd of
102cm²). Of course, this last grille is removable
as well for that ‘à la naturelle’ look—my
preferred option.
The GT 1.0’s drivers are of very high quality
and, according to Atohm, are designed
32 Australian

Atohm GT 1.0 Loudspeakers
O N T E S T
in-house. Both the tweeter and the mid/
woofer have large magnet structures and
good materials quality. The 28mm aluminium
dome tweeter is ferro-fluid-cooled and its
high-frequency response is quoted to extend
up to 30kHz. The solid machined aluminium
faceplate in which the tweeter is housed has
a shallow flare which is dimpled in a precise
pattern—Atohm calls it an ‘Anamorphic
Dispersion Pattern’ (ADP)—and says this
technique provides ‘better off-axis dispersion
characteristics.’ The mid/woofer features a
cellulose fibre diaphragm with a rubber roll
surround of specific profile (Low Diffraction
Surrounding (LDS)).
A wide and open
soundstage spreading
well beyond the speakers’
edges, very good depth,
and precisely-placed
images...
Its low-frequency performance is assisted
by means of the enclosure being a bass
reflex alignment, using a rear-facing port
(43Ø×150mm).
Atohm specifies the GT1.0’s response as
45Hz to 30kHz with no dB latitudes, its sensitivity
at 89dBSPL at a distance of one metre
for an input level of 2.83V and a 6Ω nominal
impedance. The crossover between the drivers
is quoted as being at 2.5kHz. Good-quality
binding posts are featured around the rear
and are placed just below a large rotary knob
which allows tweeter level trimming of ±1dB
for fine-tuning to room acoustics.
This is a stunning-looking little transducer:
My review samples were dressed in
an immaculately-applied gloss lacquer over
gorgeous Rosewood. The GT 1.0 is also available
in black and white piano gloss (I saw an
example of the white gloss at the distributor’s
warehouse, and it was absolutely stunning).
I quickly found that the GT 1.0 needed
a bit of running-in with the tweeter sounding
a tad forward and sibilant and the bass a
bit lean straight out of the box. Given some
moderate level music playback for a break-in
period of around 50 hours tamed and loosened
things up remarkably. In fact the bass
ended-up being surprisingly full for a speaker
of its size (that huge magnet pays dividends).
La Musique
We have all heard the term ‘disappearing
act’ when it comes to speakers… hell, some
of us lucky ones have even experienced it.
Well the GT 1.0s certainly are the archetypal
summation of that term. These speakers
project a slightly forward soundscape that
is totally independent of the enclosures; to
the point of tricking the ear-to-eye information
process. But you expect this from small
stand-mount speakers, right? Well… yes. But,
boy, these Atohms perform that trick well.
The soundscape was an amalgam of a wide
and open soundstage spreading well beyond
the speakers’ edges, very good depth, and
precisely-placed images.
Also impressive for a small speaker was
the handling of complex and dynamic
material. The GT 1.0 was adept at dynamic
contrast—more notably in the bass—in a way
akin to larger designs; quite remarkably,
actually, for such a small driver.
Any Rodrigo y Gabriela track came
across with the couple’s signature
ATOHM GT 1.0
LOUDSPEAKERS
Brand: Atohm
Model: GT 1.0
Category: Bookshelf Loudspeakers
RRP: $4,990
Warranty: Two Years
Distributor: Absolute HiEnd
Address: PO Box 370, Ormond VIC 3204
(04) 8877 7999
info@absolutehiend.com
www. absolutehiend.com
• Superb mids
• Fit ‘n finish
• Can tailor tweeter’s
response
• Impedance
• Deep bass
• No bi-wire
LAB REPORT
Readers interested in a full technical
appraisal of the performance of the
Atohm GT 1.0 should continue on
and read the LABORATORY REPORT
published on page 99. Readers should
note that the results mentioned in
the report, tabulated in performance
charts and/or displayed using graphs
and/or photographs should
be construed as applying only
to the specific sample tested.
Lab Report on page 99
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O N T E S T
Atohm GT 1.0 Loudspeakers
power and dexterity relatively intact. And
while coping remarkably well with such
difficult material in terms of dynamic
fidelity, the driver duo also excelled at
detail retrieval, instrument separation
and accuracy to harmonic structure. It’s
a fast sound too, with a sense of bee-bop
pace that jets the music along, while the
transient snap and vivid micro-dynamic
detail on tap here renders small fingernail
and steel string interactions dramatically
real-sounding.
In my test room, which is rather
large, I perceived the speakers’ upper
range to be a tad laid-back, or recessed.
The rear tweeter level adjustment was
very useful here and adjusting it appropriately
served to add a bit of sparkle
to the upper frequencies. I notched it
up to the +1 position and heard a subtle
but easily-perceptible increase in treble
detail and extension.
This level of overall sophistication
and resolution will place some demands
on your ancillary gear. As with any great
speaker, the playback source and driving
amplification need to be on-par. Also, I’d
recommend that very solid, good-quality
stands, of appropriate height, are
absolutely essential in order to place
that top-notch tweeter at ear height and
for its proper integration with the equally
adept mid/bass driver. Also worthy of
note is that as much as it’s one hell of a
little driver, so that it can’t defy physics,
it punched less like a welter-weight and
more like a middle-weight. So what it does
do is quite remarkable.
Conclusion
I was quite taken by the little Atohm GT
1.0. It is very refined in its handling of
tonal colours and delicate detail. Its amazing
sound-staging capabilities surprised
me any number of times and its dynamic
aptitude, although not quite stretching to
the level of larger floorstanders, is impressive…
especially in small to medium-sized
rooms, given the diminutive enclosure
and the size of the bass/midrange driver.
So, bearing in mind that the GT 1.0 is
the entry point to the GT range, and all
things being equal, I expect to hear even
greater things from its larger
stable-mates. It’s certainly evident that
French newbie Atohm has a very bright
future.
Edgar Kramer
LAB REPORT ON PAGE 99

L A B R E P O R T
Atohm GT 1.0 Loudspeakers
CONTINUED FROM PAGE 32
Test Results
The performance of the Atohm GT 1.0, as
measured by Newport Test Labs, was
excellent. Graph 1 shows an averaged response
measured in-room, using pink noise
as the test stimulus, and you can see that
from 100Hz to 10kHz the traces on the graph
vary by no more than ±2dB. In this case, the
upper limit is the graphing limit, but you can
see that below 100Hz, the bass response of
the GT 1.0 rolls off quite quickly, which is to
be expected considering the small size of the
bass/midrange driver and the moderate size
of the cabinet.
The second graph (Graph 2) shows the
high-frequency performance of the Atohm
GT 1.0 in detail. The measurement uses a
gating technique that simulates the environment
of an anechoic chamber. There are
three traces, which show the response at the
three different settings of the attenuator on
the rear panel. You can see that the attenuation
is not quite uniform, with a bigger difference
in level between the ‘high-def’ (+1.5dB)
position and the ‘linear’ (0dB) position than
there is between the ‘linear’ position and the
‘smooth’ (–1.5dB) position. You can also see
that although the control starts operating
at 1.5kHz, it has no substantive effect below
4kHz, so it will have no effect on fundamental
musical notes, only on their harmonics.
Atohm has done a wonderful job with its
grille design, because it’s virtually acoustically
transparent. There is a significant 2.5dB
difference across the region 3–4.5kHz, but I
doubt that this would be audible. (Graph 3.)
Low-frequency performance of the Atohm
GT 1.0 is shown in Graph 4. You can see
that the Atohm driver rolls off quite steeply
below 100Hz, to a minima at 47Hz. The
response above 100Hz is smooth: part of the
roll-off is due to limitations in the measuring
technique used (nearfield acquisition). The
port has been tuned far lower than I might
have expected: as you can see, it delivers its
maximum output at 38Hz, though the port
does contribute to the bass output significantly
from around 27Hz to 110Hz. There is
some unwanted output from the port across
the region 300Hz–1.2kHz, and also at 1.8kHz,
but because the levels involved are very low
and the port is facing away from the listening
position in any case, I don’t think they’re important.
They don’t appear to be resonances,
because they don’t show up on the
impedance modulus.
As for the impedance, the Atohm GT
1.0 is a very well-behaved design within the
audio band, never dropping below 4Ω and
when it approaches this impedance (which
it does at 20Hz, 50Hz and 200Hz) it does so
only briefly. However outside the audio band
(above 20kHz), the Atohm GT-1’s impedance
continues to fall up to the measurement
limit (30kHz), whereas it’s preferable for a
designer to ensure that his speakers’ impedance
increases with increasing frequency in
order to ensure that all amplifiers will remain
completely stable and that their automatic
(usually VI) protection circuitry won’t trip.
The nominal impedance of the GT 1.0
is technically lower than Atohm’s claim of
6Ω, with Newport Test Labs showing that according
to the IEC 60268-5 standard (Section
16.1), it should have been stated as 5Ω to
comply with IEC regs. The pair matching is
outstanding; you can barely see any differences
at all between the left and right speakers
(identified by the red and yellow traces).
Interestingly, setting the treble control to
‘high-def’ appears to have a very slight effect
on the level of the system resonances at 34Hz
and 90Hz. The differences in impedance
caused by using the treble control clearly
show why the frequency contouring is different
at the different settings (as shown in
Graph 2). Phase angle is superbly constrained
to around ±30° which is an excellent result.
The final graph prepared by Newport Test
Labs is a composite that ‘overlays’ several
graphs to give a more complete overall picture
of how the Atohm performs. This shows
that the frequency response of the Atohm
GT 1.0, as measured by the lab, is 75Hz to
28kHz ±3dB. Increasing the window by only
the smallest fraction (to ±4dB) would see
the response extend downwards further, to
just below 60Hz. Sensitivity, as measured by
Newport Test Labs, was 86dBSPL at 1 metre for
a 2.83V input. This is ‘way short of Atohm’s
claim, but is more in line with what I would
personally expect for a design of this type.
No doubt the reason for the difference is that
Newport Test Labs uses wideband pink noise
when it is testing loudspeakers, and then
averages the response over several octaves,
whereas it’s likely Atohm uses the sine-wavebased
‘spot frequency’ method that is more
commonly employed by speaker manufacturers,
largely because it gives better figures.
This—and the sensitivity and the diminishing
impedance at high frequencies—aside,
the Atohm GT 1.0 is a well-designed loudspeaker
that exhibits a flat and extended
frequency response. Steve Holding
dBSPL
110
105
Newport Test Labs
dBSPL
110
105
Newport Test Labs
dBSPL
110
105
Newport Test Labs
100
100
100
95
95
95
90
90
90
85
85
85
80
80
80
75
75
75
70
70
70
65
65
65
60
60
60
55
55
55
50
20 Hz 50 100 200 500 1K 2K 5K 10K
Graph 1. Averaged frequency response using pink noise test stimulus with capture
unsmoothed (red trace) and smoothed to one-third octave (blue trace). Both traces are the
averaged results of nine individual frequency sweeps measured at three metres, with the
central grid point on-axis with the tweeter. [Atohm GT-1 Loudspeaker]
50
400 Hz 500 1K 2K 5K 10K 20K 30K
Graph 2. High-frequency response, expanded view, showing attenuator settings.
Test stimulus gated sine. Microphone placed at three metres on-axis with dome tweeter.
Lower measurement limit 400Hz. [Atohm GT-1 Loudspeaker]
50
400 Hz 500 1K 2K 5K 10K 20K 30K
Graph 3. High-frequency response, expanded view showing response with grille on (red
trace) and grille off. Test stimulus gated sine. Microphone placed at three metres on-axis
with dome tweeter. Lower measurement limit 400Hz. [Atohm GT-1 Loudspeaker]
dBSPL
110
105
Newport Test Labs
Ohm
40
30
Deg
180
Newport Test Labs
150
dBSPL
110
105
Newport Test Labs
100
120
100
95
20
90
95
90
60
90
85
30
85
80
75
70
65
60
55
50
10 Hz 20 50 100 200 500 1K 2K 3K
Graph 4. Low frequency response of front-firing bass reflex port (red trace) and woofer.
Nearfield acquisition. Port/woofer levels not compensated for differences in radiating areas.
0
10
9
-30
8
7
-60
6
-90
5
-120
4
-150
3
-180
20 Hz 50 100 200 500 1K 2K 5K 10K 20K 30K
Graph 5. Impedance modulus of left (red trace) and right (yellow trace) speakers at +1
setting plus phase (blue trace). Dark green is 0 setting; Dark blue is -1. Black trace under is
reference 4-ohm precision calibration resistor. [Atohm GT-1 Loudspeaker]
80
75
70
65
60
55
50
20 Hz 50 100 200 500 1K 2K 5K 10K 20K 30K
Graph 6. Composite response plot. Red trace is output of bass reflex port. Dark blue trace
is anechoic response of bass driver. Green trace is gated (simulated anechoic) response
above 300Hz. Black trace is averaged in-room pink noise response (from Graph 1). [GT1]
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