The GT Series loudspeaker range reflects the desire of Thierry Comte, the one-man orchestra of Welcohm Technology based in Pin in Haute-Saône, to push back the barriers of domestic sound reproduction as far as possible.
The designer’s creativity is embodied in the latest CAD tools and then tested dynamic simulations on computers and analyzers using the FFT finite element method. The prototypes are then screened for vibration measurements by laser interferometry before the essential step of validation by the subjective evaluation of listening, merciless and indispensable arbiter. All the components and technical solutions that take place on board the top-of-the-range GT3-HD column are exclusive to the brand and form an indivisible whole, as are those of the other models in the series.
The GT3-HD column is at the top of the GT range, which includes the sparkling GT1-HD, one of the most sparkling compact speakers currently available on the world market, and the GT2-HD column, a kind of GT1 with a more muscular bass. From a technical and technological point of view, the three speakers share the same roots, the same spirit, the same DNA. However, the GT3-HD takes a more royal, sovereign approach with specific loudspeakers and very high specifications. There is a real consistency of range within this series imagined by the manufacturer, each superior model being directly derived from the previous one in an indisputably more sophisticated and therefore more efficient version. If we can consider the GT2-HD as a GT1-HD that would have been grafted with a subwoofer, the GT3-HD can be seen as a GT2-HD whose every component has been perfect, has been optimized, has been the subject of even less compromise.
The GT3-HD is a three-way column and four speakers, each bass, midrange and treble register being distinctly assigned to two 18 cm boomers, a 15 cm midrange driver and a 28 mm dome tweeter respectively. The agreement remains bass reflex and takes into account the fact that the two woofers that equip the loudspeaker play together in two thirds of the overall volume of the cabinetry made of MDF with lamination of 3 mm plates for the curve of the side walls. As with the GT2-HD, the tuning vent opens under the speaker, which rests on a decoupled base. Internal reinforcements placed near and between the midrange bass transducers stiffen the structure under good sound pressure. The midrange transducer plays alone in its own closed room, so it is acoustically isolated from both boomers. It is mounted in a cavity called PRD for Progressive Rear Damping, filled with damping material and whose cone-shaped rear surface gradually compresses the wave that is then damped. It is converted into heat and can no longer return to the membrane, which results in a very smooth and precise sound, especially on the transients.
A REAL BUSINESS CARD
The GT3-HD is the brand’s technological showcase. The speakers are from the Absolute Series. The bass is therefore reproduced by a pair of LD180s that operate up to 250 Hz. The diaphragm of this bass driver is lightened by eight holes around the core cover in order to decompress the copper-ringed core as much as possible and to cool the 35 mm diameter and 22 mm high copper coil wound on a Kapton and Nomex support. The enormous ferrite of 12 cm in diameter contributes greatly to the excellent sensitivity of these two units. The medium is provided by an MLD150, which covers the range from 250 to 2500 Hz, the specific alloy diaphragm is mounted on a special profile LDS suspension that pushes the progressive arrival of the first fractionation beyond the useful operating range. A solid aluminium anti-vortex warhead improves directivity and helps to cool the magnetic motor and the 25 mm diameter copper coil simultaneously. In addition, the spider and suspension have a generally constant and symmetrical stiffness coefficient so as to ensure equidistant elongations with respect to the rest position and to impart a restoring force proportional to the movements in both directions. The 100 mm ferrite FWI (Force Without Inductance) magnetic circuit extends the notion of symmetry by creating a symmetrical field around the rest point of the 25 mm diameter copper coil in the 6 mm long air gap of the MLD150s. The inductive influence of the coil has been reduced by the installation of a copper ring on the specific geometry core. As for the SD28 ND04 RD tweeter, «the» GT tweeter, it operates above 2500 Hz and the 28 mm treated silk dome climbs to 30000 Hz. The neodymium ring magnet unlocks the sensitivity measured originally at 98 dB. The CCAW coil, for Copper Clad Aluminium Wire, is mounted on an aluminium support. It is shorter than the air gap to ensure constant flow even on large displacements. The very high flow in the ferrofluid submerged air gap releases the dynamic capabilities of this loudspeaker. As with the MLD150, a copper ring core reduces inductance and linearizes the response curve while reducing intermodulation distortion. The profiled and granular front face of the tweeter is made of die-cast aluminium according to an ADP (Anamorphic Dispersion Pattern) profile which ensures excellent off-axis dispersion.
To guarantee the best temporal alignment of the loudspeakers, to ensure that the phase of their emissive centre is properly respected, a specific TCC filtering for Time Coherent Crossover or temporal coherence filter meets this need, it integrates a time calibration cell, in practice an electronic delay line, on the acute channel. This cell allows the use of a first-order cut-off slope to limit phase rotations at the connection frequency. Various correction cells for various physical phenomena inherent in a loudspeaker system are also inserted. The GT3-HD has two three-position switches -2 dB, 0 and +3 dB to adjust the frequency response of the midrange registers, between 500 and 2500 Hz, and treble registers from 2500 Hz, for a total of 9 possible combinations. The internal damping of the cabinetwork uses cotton felt and Dacron. However, given the «tube» appearance of this tall column, the problem of the reflection of the first resonance waves between the walls of the column enclosure much higher than wide and deep remained to be solved. As with the GT2-HD, the GT3-HD was added a laminar absorption cavity in the top of the enclosure by throttling the section behind the medium volume. This acoustic transformer ends with a volume filled with damping material perfectly dosed behind the tweeter. The principle called SWD for Standing Wave Damper, channels the back wave which is then damped, the first resonances are then cancelled. At the bottom of the enclosure, another cavity has been built on the height of the cylindrical vent, which can receive a few litres of sand if necessary, which will reinforce the stability of the enclosure on the ground. The GT3-HD’s base consists of two bases, the underside of the GT3-HD and the base itself, which introduce a progressive decoupling called PDS for Progressive Damped Spiking. Through two sets of cones, one between the column and the base, the other between the base and the ground, and spacers between the enclosure and the base under stress from the weight of the enclosure, residual vibration energy is absorbed by the massive underside of the column.
THE SET UP
We had the opportunity to listen to the GT3-HDs, among others, in a rather spacious room of about fifty square meters, and we were struck by the ease with which these speakers know how to appropriate the space. We thank New Tone and Jean-Michel André for this demonstration. These beautiful columns were combined with an integrated Micromega M-One amplifier, with which they got along very well. GT3-HDs are not difficult to power, but their potential argues for qualitative as well as quantitative amplification! In terms of placement, we would advise you to keep a respectable distance from the corners of the room. Indeed, the energy deployed by GT3-HDs can be quite high, and the radiation induced at this point will be detrimental to the readability of the message. With respect to the rear wall, the problem is less difficult because the decompression vent radiates towards the ground. But still observe a good thirty centimetres.
0, 30° directivity curves.
Absence of marked directivity, low and perfectly regular attenuation, will result in a great stability of the stereo image and a good focusing of the soloists.
Impedance versus frequency curve.
Curve of a particular system of 3 channels + 1 bass reflex. The filtering, in soft slope, integrates a module of temporary shimming on the treble allowing to compensate for the p&ysical offset of the motor coils (TTCTM technology). The cabinetwork physically provides an impedance adapter and acoustic filter (SWDTM Technology).
Curve per third of an octave in the axis.
Representation of the three settings Smooth / Linear / High Definition. The attenuation is constant and perfectly regular, proof of the extreme rigour in the filtering design.
Extremely fast damping. This is partly the result of the combination of SWD and PRD technology, which respectively treats the standing wave at the top of the cabinet and provides progressive damping of the medium independently. Reflection of a true know-how.
For the first few minutes of listening, we were satisfied with chaining the tracks and enjoying the music without trying to analyze it. Indeed, the GT3-HDs have given us a playful, joyful and truly rewarding performance, especially since the eclectic music lover will be able to alternate large and small ensembles, baroque and techno, jazz and pop. GT3-HDs are not sectarian. On the other hand, they have their own way of embracing you in their universe. In the latter, the recorded music is reproduced on a large scale, with wide basses that extend in width and depth without attenuation. These columns are not stunted, but they are not barred by 38 centimetres either.
And yet, they know how to deliver a very well behaved bass, which ventures particularly low, with a lot of information. High frequencies are also a celebration, with an elegant signature that combines when modulation demands it. The voices are thus crunched frankly, with a beautiful light and all the required precision. They are solid reference points to validate the degree of naturalness towards which a speaker is capable of reaching. The same applies to acoustic instruments with which it is difficult to cheat, as well as to any reference point that is easily identifiable in reality. Here, we admire the neutrality of the GT3-HDs associated with a kind of listening comfort that is never denied, even when the sound becomes thick, even on particularly complex formations. Finally, one of the most attractive features of GT3-HDs is their ability to put recorded music into perspective. We will not hide from you that we attended a demonstration where their position placed them very advanced in a vast room, and that they made us enjoy an absolutely exceptional sound scene. Certainly the work of phasing was masterfully concluded by their designer. By closing our eyes, we were simply unable to locate the speakers in the room. On the other hand, we were able to witness the meticulous reproduction of a vast, coherent and phenomenally accurate three-dimensional image.
We had an undeniable pleasure living for a while with the GT3-HDs. They are chameleon speakers endowed with an innate sense of melodic coherence and capable of imposing a powerful rhythmic connivance with their owners. They are speakers with which we experience music more than we observe it. In addition, their ability to play (very) loudly without giving any sign of weakness is a plus that will win the opinion of music lovers who appreciate living music. This is further proof (but was it necessary?) that the French are able to design and manufacture speakers worthy of comparison with the finest in world production.
240 x 1190 x 435 mm
35 Hz to 30.000 Hz
Up to 300 W RMS (800 W peak, less than 400 ms)
92 dB/2.83 V/m