
This article first appeared inย The Sound Advocate, a HiFi publication that offers โSound component reviews and commentary For The Discerning Listener!โ
In my 40 years as an avid audiophile, I have seen about everything there is regarding speaker design. From weirdly shaped enclosures that try to break the laws of physics that govern the rest of the speaker-designing community to simple one-driver designs that take on the full range of musical frequencies with one driver. All speaker designers take different approaches to yield the same result for the most partโthey are trying to bring to life a recorded musical event like it is being played for you in your home, or even better, to transform your living room into the room where the event was being played!
The issue comes with the fact that we listeners are human. This means our ears are all sensitive to various frequencies and how our ear/brain processes these sounds. This complicates an already complex issue, namely, having a speaker that is true to the music but at the same time caters to ourย hearing and perception.ย That is all we can ask for in a speaker: to stay true to the music as much as possible while catering to our sensibilities and the type of system/room we put them in.
Atohmย is a French speaker company that has been on the scene since 2000. Its founder, Thierry Comte, started the company after working as the technical director forย Triangle, another French speaker company. They started out making OEM drivers for other companies, including Triangle.ย A few years later, Atohm entered the finished speaker market with various models at different price points. Now, they offer finished speakers and separate drivers to the public.
Theย GT HD seriesย is their newest flagship speaker line, and I have been spending some quality time getting to know the GT3-HD tower speaker. GT, in this case, is cleverly named the โGrand Thrillโ series. Atohm says their speakers are for the Grand Thrill of the music.
While theย GT3-HDย looks like a simple tower speaker design at first glance, a lot is going on here that must be understood to see Atohmโs vision for a flagship speaker in this price class. Atohm is a company that is very transparent about the technologies and designs they use in the GT series. The company published what it calls its Technical Book about the GT series speakers, which goes into much more detail than I have the space to do here. I recommend to anyone interested in speaker design or these speakers that they read it because it is thorough and intellectually written. But I will touch on the essential parts of the design.
I like it when companies are open about their design decisions and donโt try to hide behind big words or explanations that we non-engineers canโt understand. When a speaker company can explain its choices to the public, it creates transparency and gives a would-be owner a little more confidence in their purchase decision.

The SD28 ND04 RD tweeter is used in the GT series and was chosen for its soft, accurate, and refined response. It is fitted with a powerful neodymium ring magnet, which puts sensitivity at 98dB/watt. This high sensitivity is attained without a waveguide or horn pressure chamber. A copper ring is added to linearize and reduce inductance, which helps the response at higher frequencies and minimizes intermodulation distortion. The voice coil is made of copper-clad aluminum wire or CCAW wire, which provides good conductivity but is also lightweight for better performance.
The front panel of the SD28 tweeter is made from injected aluminum for rigidity and vibration elimination, and it uses ADP(Anamorphic Dispersion Patterns) technology. These small-spaced debits on the inner front cover offer better off-axis dispersion and limit interfering reflections at very high frequencies.

The 6โ midrange driver in the GT3 HD is specially made for the GT3. The ML150 has a unique alloy cone that Atohm says is much better at keeping its rigidity than paper or other plastic cones. This allows the ML150 midrange driver to handle a frequency range from 180Hz to 2500Hz. This is a lot of musical information for the midrange driver to cover, so it needs to be both rigid and controlled in its response.
This driver has no dust cap; instead, it is fitted with a phase plug that helps with phase and directivity. The coil length for this driver is also reduced to 10mm, which allows the rated sensitivity of this driver to be at a very good 94dB. In my listening, the ML150 driver covered its wide frequency range well and delivered good detail while keeping things smooth and even.

The LD180 7โ bass driver was also designed solely for the GT3-HD speaker. This driver shares the same alloy cone construction as the ML150 midrange, which allows for a more natural transition between them. This driver features an 11mm maximum extension and eight strategically placed holes in the base of the cone to maximize decompression of the core and coil cooling while minimizing flow noise. All this technology results in a bass driver that can reach high sound levels with low levels of distortion and compression.
CROSSOVER
The crossover is an essential and often overlooked part of a high-end speaker. Most people overlook it simply because they cannot see it or do not understand what it does or how it works. Through years of research and lessons learned from their earlier designs, Atohm designed the crossover in the GT series with what Atohm callsย โtemporal calibration cells (delay line)โ.ย This time domain correction allows Atohm to use 1stย order filters in the treble range and a gentle 6dB per octave slope in the crossover.
This slope allows Atohm to add separate โcellsโ that control any phase or response issues with notch filters or impedance compensation networks. I like that Atohm uses lower-order filters with their design, as anyone who has worked with crossovers will tell you that the more complex and higher order you make your crossover filters, the more phase and impedance issues will creep in and cause problems.
This is also a testament to how well Atohm designed their drivers, as many speakers on the market use high-order filters to keep cone breakup or other driver-focused issues from appearing in the final response. In my experience, a high-quality driver made with todayโs technology or know-how should not need aggressive filters or high-order crossover networks to hide cone breakups or issues caused by the driver.

One of Atohmโs most remarkable features is its tunability. The crossover features a tweeter and midrange level control that allows the user to โtailorโ the response to either their room or their sensibilities. This is an excellent idea that has been lost over the years.
Speakers back in the 70s and 80s used variable L-Pads that could change the level of the tweeter or midrange. But these variable L-Pads played hell on the signal integrity and generally would do more damage than good to the music signal. Atohmโs approach is different. They use high-quality resistor networks and multi-way switches, allowing you to switch the output levels of tweeter and midrange drivers. According to Atohm:
โThe GT3 column speaker features two switches with three positions: the first switch is for frequencies ranging between 500 Hz and 2.5 kHz, and the second one is for frequencies between 2.5 kHz and 30 kHz with intervals of 2 and 3dB, or a maximum of 5dB amplitude adjustment. In total, the GT3 can offer 9 different frequency responsesโ.
The 6db crossover networks used in the GT3-HD mean that the changes made by these switches are gradual and cover a broader range of frequencies than most contour controls. This allows these differences not to be so drastic and will enable users to control how the speakers sound in their room gradually. This is impressive, as Atohm added these features without resorting to cheap, lower-quality parts or methods. In practice, I could hear the differences between the settings and spent much time finding the best ones for my room.
My room has excellent reverb characteristics, so, in the end, I found that the stock โlinearโ setting gave me the best performance. Considering where speakers are placed in todayโs homes, having these controls is something more companies should look into, but only if they are implemented in a way that does not disturb or take away any of the crossoverโs functions, clarity, and detail.

The enclosures on the GT3-HD were carefully designed and tested to keep its behavior from disturbing the delicate frequency response or causing any resonance. The top part of the cabinet is treated with laminar damping material that traps and then dampens out any standing waves. However, the air flowing into this chamber must go through an acoustic filtering damping material applied in a measured quantity to cancel out any reverberation built up in the cabinet.
The cabinet behind the midrange driver is treated with what Atohm calls itsย PRD(Progressive Rear Damping) technology. The midrange, first and foremost, is in its enclosure; this keeps the midrange isolated from any pressures or resonance from the woofers. The back panel on the midrange enclosure is cone-shaped and lined with increasingly-compressed damping material, to prevent any standing wave from returning to the midrange cone. This is an essential part of this design. The midrange is the heart of the music, and the part most people are most sensitive to when it comes to issues. Standing waves, resonances, or frequency response anomalies will stand out like a sore thumb.
In my review, I noticed the midrange was very detailed and clean on the GT3-HD. This shows that in speaker design, everything matters. This includes anything that can be done to keep the drivers working perfectly and the enclosure from changing that fact or adding anything themselves.
At the bottom of the cabinet is the Atohm symbol, another feature of these speakers. But this โsymbolโ is not just another badge showing the company that made your speakers. This is a removable cover for the sand compartment in the speakersโ base. This compartment holds up to 4 liters of dry sand to help anchor the speakers to their position and stamp out any vibrations in the cabinet. Of course, these being review samples, I did not want to risk damaging the speakers or making a mess, so this feature was not tested in my review.
The bottom of this cabinet is also where the bass port is for the GT3-HD. This is a bottom-firing port that fires out from all four sides of the cabinetโs bottom plinth and should make positioning easier in most rooms due to the portโs air forces not being directed to any one side of the speaker.
Also, for positioning flexibility when close proximity to walls cannot be avoided, a port plug is included that will allow a little tighter bass tuning. This might cause a little loss in low bass extension, but the bass will be tighter and sound more musical when the speakers are placed near a wall. ย
PDS(Progressive Damped Spiking) is a technology that Atohm devised to isolate the speaker from the floor so that little to no energy is transferred between the two. Two braces connect the main speaker cabinet to the plinth. Energy is passed through these braces and into the plinth only to return through the secondary spikes that are a part of the central spikes touching the floor.
When the speaker is placed on the floor, the speakerโs weight compresses the braces just enough to make contact with the secondary spikes, which will dissipate any vibrations back into the cabinet and not the floor. In my testing, I noticed no issues with floor vibrations or any transferred energy in my measurements or listening.

The GT3-HD cabinets are made of high-quality MDF. The curved side panels are formed using multiple layers of 3mm wood and fixed in a curved mold until the glue sets. Then, they are precision machined to create the final cabinet shape.
A laser vibrometer is used to determine where to place cabinet supports for the best vibration and resonance control. The finish options for the GT3-HD are white piano, black piano, and rosewood piano finish (my review samples were impeccably finished in the rosewood veneer).
When I was reviewing the GT3-HD, everyone visiting my home complimented their very well-finished exterior and design characteristics. Once I showed them some of the technologies in the design, they praised the GT3 for its elegance but also that it looked like a well-appointed speaker and not some over-the-top odd-looking design that only eccentrics and complete audio nerds would like. The GT3-HDs are very well built, and their finish is expertly done.
The grilles are not generally something that get much attention in speakers and is primarily a simple cover with either a pin or magnetic lock. Atohm takes this idea one step further by offering two options. The main grilles are a simple cover that fastens magnetically. They end at the bottom in a spear-like point, which gives the grille a cool appearance. Many people will take the grilles off for serious listening or never put them on in the first place.
This is mainly because no matter how acoustically transparent the grille cloth is claimed to be, it will affect the audio. Atohm gave a second option, individual metal- and cloth-covered covers, for each midrange and bass driver. Not only does this offer a different appearance, but, with the tweeter already having a metal mesh protective cover built into the tweeter front plate, this option allows for nothing else to be between the tweeter and the listener.
Like with every speaker review, I do my listening without grilles. I applaud Atohm for offering two different options for folks who donโt want to look at the raw drivers in their speakers or have children or pets who could venture too close to the drivers and damage them.
Atohm builds their speakers in-house from start to finish. I am glad to see Atohm keeping manufacturing local. It makes for an often better overall product and gives people who live in those areas another employment opportunity they would not have if the manufacturing were contracted elsewhere.
Performance
Like any speaker I review, I take the time to make sure the speakers are broken in (I know, controversial) and make all the adjustments needed to get the most out of them. For the most part, the GT3-HDs were straightforward to get ironed out. The speakers were toed in about 12 to 15 degrees, which gave the best combination of soundstage width and imaging accuracy. The speakers ended up about 8.5โ apart and about 4โ from the front wall, which also gave the best bass definition while keeping the soundstage deep.
While these speakers are relatively thin by design, they are pretty tall, which made me worry about tweeter height and listening position. But all was good. Atohm obviously knew this in making their design, and the speakers sounded nicely balanced, even though they are taller than speakers I usually have in my room.
When I first sat and listened to the GT3-HDs, their performance put me off. I was using my Pass Labs X150.5 power amp and Hegel P20 preamp. For some reason, that combination did not sound natural and made me pause. But when Emilios Mandalios from Audio Excellent followed up the GT3-HD with anย Atoll IN300ย (review coming!) for me to try, my mind was changed. While my Pass/Hegel combo did not match well with the GT3-HD, the Atoll IN300 seemed to be perfect for them.
Graveyardโs new 2024 album โ6โย is an album I have been waiting for. This Swedish bandโs songwriting ability and playing style have always impressed me. With the album โ6,โ they slow things down and draw from their โ60s and โ70s inspirations from bands like The Doors and other rock bands of that time. Every song tells a story and is inviting to listen to (if you are a stoner rock fan like me). I listened to this album several times with the Atoll/Atohm GT3-HD combo and liked what I heard. The bass was tight (not as tight as my open baffle but good) with good impact and great depth. I would not think users of the GT3-HD would ever need subwoofers unless you are a bass head. I ran measurements in the room, and I got 25hz solid bass in my room. For two 7โ woofers in each cabinet, that is impressive.
I took this in-room frequency response measurement when I got the speakers in their final position. You can see that the bass performance is impressive for a slim tower speaker with no subwoofers. Also, from 1k and up, you could not ask for a smoother and more linear response in a room.

There are a couple of dips, one at around 700Hz and another at around 280Hz. However, these might be room-related. Also, most 3-way speakers have more complex crossovers and can sometimes show phase-related anomalies around the crossover points. Otherwise, this is very close to a textbook response and one of the better in-room responses I have seen in a while for a commercially available speaker.
I have seen a trend in some speakers bumping the midbass up or boosting the presence region. To me, the added midbass or boosted treble does nothing but cause either listening fatigue or a sense of unnaturalness in the bass. I had to mention this because it is refreshing to see a speaker that measures well in the room and has a straightforward design. Itโs just a good design that is tuned well.
I understand some speaker designers โtuneโ their speakers for a specific response, and I have been guilty of doing that myself with some of my speaker designing and building. Some designers will tune in some variability for room conditions or to smooth out an area they feel needs to be deemphasized. But the Atohm does none of that and just sticks to good engineering and a good measured frequency response.
Christoffer Moe Ditlevsen is a composer that everyone needs to hear on a good system. His recordings are great, and his writing is stellar for the type of music he makes. The albumย Midst of Lifeย has to be one of my favorites. It is a short three-song album, and the songs themselves are short, but the amount of enjoyment I get from listening to them is enormous. On the Atohm GT3-HD, all of the detail was there. The cellos had good authority in the room, as they should on these tracks, and the violins also showed their stuff. The bass was deep and impactful while the treble was smooth and musical.
The Atohm-designed soft dome tweeters are good. While they didnโt deliver beryllium or AMT/Ribbon levels of detail, I could listen to the GT3-HD all day without fatigue. With audio, there are always tradeoffs. This is where Atohmโs tweeter falls in. It serves you a good dose of musical accuracy and transparency but serves it to you in the most comfortable and silky way possible.
As I have gotten older, I have consistently chosen the latter sound. I have listened to these tracks with my reference, highly modified Spatial Audio open baffle speakers, probably hundreds of times. In comparison, the Atohms presented the performance very differently.
The Atohms are the more mannered and gentlemanly of the two, serving up slightly more control. But my Spatialโs have dynamics for days, and let me hear every level change from the instruments. The Atohms went lower in the bass, but I cheated by using my REL sub with the Spatials, so that was a wash.
But in the midrange, I heard magic from the Atohms. Driven by theย Atoll IN300,ย the GT3-HD had a fast, incisive, and natural midrange. The ML150 midrange driver is by far the star of the show. The strings sounded fantastic on the Atohms driven by the Atoll. On other tracks I tried, the vocals sounded crisp, with great leading and trailing edge detail, and without sibilance. It is quite something when you hear crystal clear word pronunciation in the vocals that show every breath and detail of the voice without darting into sibilance when things get loud or the vocals go falsetto.
I wish it had worked out with my reference Pass Labs/Hegel combo, but it was not to be (what does this imply? โ editor). My reference modified Spatial Audios deliver great vocals and string transparency, but this was one area where the Atohms took center stage. Midrange clarity and detail are paramount to delivering an enjoyable and accurate experience in music.
As far as choosing one or the other, I think both my Spatials and the Atohms get many things right with this music. Both models are accurate, deliver good imaging and soundstaging, and produce great bass energy and detail. And again, where the Atohm takes it home with a killer midrange, the Spatials bring that high sensitivity and sense of effortless dynamics that large open baffle drivers bring, and it is hard to ignore. So, all in all, I believe both are right, and both win for different reasons.
Conclusion
I thoroughly enjoyed my time with the Atohm GT3-HD and think it is a well-designed and built speaker. If you read their technical bulletins like the one that came with the GT3-HD, there is no doubt that Atohm knows how to design speakers. The company keeps their designs simple and elegant, and tops them off with excellent finishes and grille options.
Atohm makes their drivers in-house, so they have more ultimate control over the driversโ performance. The crossover designs are unique in that you can tune the midrange and tweeter by a few dB to help address room issues or suit preferences.
While I did try this out, and it worked flawlessly, setting the controls to the stock positions gave me the best sound in my room. I did not know what to expect when I asked to review the Atohm speakers at Axpona this year, but I am glad I did. In my opinion, if you are in the market for a floorstanding speaker in the price range of the GT3-HD, I recommend you hear them if you can. They perform well and might be just what youโve been looking for.ย Highly recommended.

Review System:
Speakers: Spatial Audio M3 Turbo S open baffle./ REL T9x subwoofer.ย
Digital:ย Denafrips Venus II, / Modified PC-based Music server/streamer. PS Audio Airlens Network Streamer.
Analog:ย Pro Ject X2 B Turntable, Darlington labs MP-7, and SU-7 phono preamp, Audio Technica AT33 PTG/ii cartridge.
Amplification:ย Hegel P20 preamp. Pass Labs X150.5 power amp.ย Conditioner: PS Audio Quintet.
Cables:ย Iconoclast Series 2 SPTPC speaker cables,IconoclastGeneration 2 ETPC XLR cables and Gotham 4/1 RCA interconnects, Iconoclast BAV REL subwoofer cable.
PRICE: US$ 13,995
Email:ย contact@atohm.com
Website:ย www.atohm.com
North America distributor:
Emilios Mandalios
Audio Excellent
Phone: (847) 774-4619 Email:ย info@audioexcellent.com
For more articles like this, visitย The Sound Advocate, a HiFi publication that offers โSound component reviews and commentary For The Discerning Listener!โ
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