BlieSMa T34T-4 34mm TeXtreme dome tweeter review

  What and why am I testing?

Today we're going to talk about the sixth element. No, not the comedy The Sixth Element starring Leslie Nielsen, nor the sixth element of the periodic table - which, incidentally, is carbon. We're talking about the sixth member of BlieSMa's T34 tweeter family: the brand-new T34T-4, featuring a 34 mm dome diaphragm made from TeXtreme® carbon (!) fiber.

Until now, the T34 tweeter family consisted of five models:

• T34A-4 with an aluminum dome (review)
• T34B-4 with a beryllium dome (review)
• T34D-4 with a diamond dome (review)
• T34P-4 with a paper dome (review)
• T34S-4 with a natural silk dome (review)

Finally, in July 2026, BlieSMa introduced the sixth member of the family - the T34T-4. With its release, the company has completed a vertically integrated lineup of TeXtreme® diaphragm drivers across all chassis sizes: the 7" W137T-854 woofer, 7" M142T-6 midrange, 3" M74T-6 midrange, 1.3" T34T-4 tweeter, and 1" T25T-6 tweeter. This gives loudspeaker designers the opportunity to build complete systems using TPCD drivers from the lowest bass all the way up to the highest frequencies.

The T34T-4 is built on the same platform as the other members of the T34 family and inherits all of their well-known features: an extremely powerful and highly linear motor with a 2.2 Tesla magnetic flux density in the gap, an ultra-light moving assembly with an impressive 3 mm peak-to-peak linear excursion, a copper sleeve on the pole piece, a titanium voice-coil former, and highly flexible, durable lead-out wires. There is only one difference - the variable-thickness dome diaphragm is made from TeXtreme®.

I particularly appreciate companies like BlieSMa that offer the same driver platform with different diaphragm materials. Rather than pursuing a single "correct" sound, they provide designers and enthusiasts with a broad palette of sonic flavors and tonal characters. This makes it possible to fine-tune the voicing of a loudspeaker more precisely and ultimately satisfy a much wider range of musical tastes and listening preferences.

Finally, I would like to express my sincere gratitude to Stanislav Malikov, founder and chief designer of BlieSMa, for kindly providing the tweeter samples for this review.

Here you can get familiar with the BlieSMa history.

  What did the manufacturer state?

The datasheet is concise yet contains all the essential information required by a loudspeaker designer.

Among the published specifications, the following deserve special attention:

• Extremely high magnetic flux density in the voice-coil gap: 2.2 Tesla
• Very high sensitivity: 96 dB (2.83 V/1 m)
• Exceptionally low inductance: 0.008 mH
• An impressive ±1.5 mm linear excursion
• A remarkably low moving mass of just 0.3 g, especially considering the relatively large 34 mm dome

The mechanical drawing depicts the tweeter with only half of its protective grille installed, subtly indicating that it is available both with and without the grille. The grille is held in place solely by the motor's magnetic field, whose attractive force is so strong that adhesive is completely unnecessary. In practice, this makes the grille fully removable, providing an additional advantage for designers wishing to experiment with custom waveguides.

  Visual inspection

The tweeters come in a matched pair.

In general, the tweeter looks very solid and weighty, the design is well thought out, and there are not the slightest complaints about the workmanship.

  Impedance frequency response

The plots below show the impedance magnitude versus frequency for the two tweeters of the matched pair, displayed at different vertical scales:

The impedance curves match each other very well, although there is an offset of approximately 0.1 Ω in their absolute level. This is of no real concern - the important thing is that the frequency responses are closely matched.

The measured resonance frequencies are Fs₁=736 Hz and Fs₂=765 Hz, both slightly below the specified value of 770 Hz.

Across the entire frequency range, the impedance curves are exceptionally smooth, showing no obvious signs of parasitic resonances or other defects in the moving system.

The rise in impedance with increasing frequency is extremely small, thanks to the exceptionally low voice-coil inductance of 0.008 mH. This has been achieved through a combination of a low-turn-count voice coil and a copper sleeve on the pole piece in the motor assembly. It is a hallmark of a well-engineered motor and contributes to reduced nonlinear distortion.

Overall, the impedance response is about as close to ideal as one could hope for, reflecting both an outstanding motor design and a superbly balanced moving assembly.

  On-axis frequency response (at 315 mm)

Below are the unsmoothed on-axis frequency response measurements for the two tweeters in the matched pair. The responses were measured in a 1650×1100 mm test baffle at a microphone distance of 315 mm, using a drive voltage of 0.5 V, and then normalized to 2.83 V/1 m:

The frequency responses of the two matched tweeters are virtually identical across the entire frequency range. Superb!

The measured sensitivity is approximately 97 dB, which is about 1 dB higher than the specified value. The overall shape of the frequency response closely matches the datasheet and is, if anything, even smoother. The response is exceptionally smooth up to 23 kHz and essentially ruler-flat above 2 kHz. The total deviation over the 2–23 kHz range remains within ±1 dB.

Above the audible range, the diaphragm transitions from pistonic to breakup operation, manifested by a pronounced 14 dB peak at approximately 30 kHz, corresponding to its primary breakup resonance. This is a remarkably high resonance frequency for a 34 mm dome. Interestingly, it is identical to that of the T34A-4 aluminum dome tweeter, yet achieved with a noticeably shallower dome profile - an advantage that helps reduce the moving mass and improves compatibility with waveguide designs.

  Off-axis frequency responses (at 315 mm)

Below are diagrams of off-axis frequency responses - conventional and normalized, in which the axial response is taken as a reference, and the off-axis ones reflect only the difference with it:

At all angles, the frequency response remains virtually unchanged up to 2.5 kHz. Beyond this point, the curves begin to separate and roll off smoothly and monotonically with both increasing angle and frequency, all the way to 30 kHz. Even in the diaphragm's breakup region, the off-axis behavior remains exceptionally well controlled. No hidden resonances or other irregularities were observed.

Overall, the directivity is impressively wide for a 34 mm dome - indeed, even wider than that of many 1" tweeters.

  Harmonic distortion (at 315 mm)

Shown above are the harmonic distortion plots measured at 2 V and 11.2 V, corresponding to sound pressure levels of 94 and 108 (!) dB respectively. The measurements were performed on-axis at a distance of 315 mm from the tweeter to the measurement microphone.

To prevent power overload and excessive diaphragm excursion during distortion measurements, a second-order analog active high-pass filter with a cutoff frequency of 800 Hz was used. Therefore, in these graphs we analyze the frequency range from 800 Hz and above.

Throughout the entire operating range, the second harmonic dominates by a wide margin over all higher-order harmonics. It reaches its lowest level between 4 and 12 kHz. Even at a sound pressure level of 108 dB, the higher-order harmonics remain exceptionally low, not exceeding 0.06% for the third harmonic and 0.01% for the fourth and fifth harmonics over the 3.3–10 kHz range.

The harmonic distortion spectrum retains the same overall structure regardless of sound pressure level. A noticeable rise in the higher-order harmonics is observed between 2.5 and 3.5 kHz. Below 2.5 kHz, the distortion is extraordinarily low for a tweeter, particularly with respect to the second harmonic.

Overall, the harmonic distortion profile is characteristic of the T34 series tweeters with rigid dome diaphragms (T34A-4, T34B-4, T34D-4). Above 3.3 kHz, I would rate the overall distortion level as very low.

  Voice coil current harmonic distortion

Despite its simplicity, this type of measurement is a very useful tool for assessing the linearity of a driver’s motor. The diagram above show the harmonic distortion measured at 2 V, corresponding to sound pressure levels of 94 dB.

To prevent power overload and excessive diaphragm excursion during testing, a second-order analog active high-pass filter with a cutoff frequency of 800 Hz was used. Therefore, in these graphs we analyze only the frequency range from 800 Hz and above. Please note that the distortion scale in the plot has been extended down to −120 dB, instead of the more commonly used −100 dB. This expanded scale makes it easier to reveal extremely low-level distortion components that would otherwise remain hidden.

Voice coil current nonlinearity directly reflects the nonlinearity of the mechanical force driving the diaphragm, since this force is related to current by the simple relationship F=B×L×I, where B is the magnetic flux density, L is the length of the voice coil wire within the magnetic gap, and I is the current. Therefore, in the frequency range where the contribution of moving-system nonlinearities becomes negligible, it is practically impossible to achieve sound pressure distortion levels lower than the current distortion.

The second harmonic dominates throughout the entire frequency range, but its level in the voice-coil current is significantly lower than in the acoustic output. This indicates that the motor is more linear than the moving assembly.

One particularly interesting observation is that below 2 kHz, the second harmonic in the sound pressure begins to decrease with falling frequency, whereas the second harmonic in the voice-coil current continues to increase. As a result, at 1 kHz the current's second harmonic actually exceeds that of the acoustic output. This suggests the presence of a mechanism by which the moving assembly partially compensates for the motor's nonlinearities.

The behavior of the remaining current harmonics is typical of dome tweeters in general: they reach their lowest levels at high frequencies and inevitably rise toward the low end of the operating range.

The fourth and fifth harmonics reached the noise floor of my measurement system at approximately −115 dB. Likewise, the rise in the third, fourth, and fifth harmonics above 6 kHz is not caused by the tweeter itself, but rather by the limitations of the measurement setup.

Overall, I would rate the level of current harmonics of all orders above 2 kHz as extraordinarily low for a dome tweeter. Excellent!

  Step response

The step response is essentially the mirror image of the frequency response, from which it is derived through a unique mathematical transformation. It is one of the standard methods for analyzing linear systems, allowing the system’s response to external excitation to be examined in the time domain rather than the frequency domain.

The T34T-4 exhibits the characteristic step response of a well-designed dome tweeter: an almost instantaneous rise, reflecting its exceptionally high upper cutoff frequency of well over 40 kHz, followed by a rapid return to rest with only a small negative undershoot. This behavior is typical of tweeters with a very gentle low-frequency roll-off, corresponding to a second-order high-pass response with a relatively low Q. In simpler terms, it is exactly what one would expect from a tweeter with a very gentle roll-off towards low frequencies.

The oscillatory tail on the decay is caused by the diaphragm's primary breakup resonance at 30 kHz. Once this resonance is suppressed by the notch filter in the crossover, there will be virtually no trace of this ringing.

  Waterfall

The waterfall plot is another tool for linear system analysis. It illustrates how the frequency spectrum of the response decays over time and often helps reveal hidden resonances that may be difficult to detect using other types of measurements:

Within the audible frequency range, the waterfall decays very rapidly - by the second time slice, virtually all stored energy has disappeared. No hidden parasitic resonances or other delayed energy-storage mechanisms were observed. The slight irregularities visible between 3 and 5 kHz are caused by parasitic reflections from the edge of the measurement baffle and are not related to the tweeter itself. This artifact becomes more pronounced as the tweeter's dispersion widens.

In the ultrasonic range, a relatively short, rapidly decaying tail is visible, corresponding to the diaphragm's primary breakup resonance at 30 kHz. After approximately 2 ms, it has completely vanished. There is no practical reason to worry about this resonance, since it lies well beyond the audible range. Purists with hearing worthy of a bat can always suppress it with a notch filter, after which it disappears from the waterfall plot entirely.

  Listening impressions

As usual, once the objective measurements were completed, the microphone handed the baton over to my ears. This time, in addition to the customary "in-hand" listening evaluation, I also had the opportunity to assess the tweeter under real-world conditions - in the PuriBliss-6p34twg two-way bookshelf loudspeaker - and compare it directly with the T34B-4 beryllium tweeter installed in the PuriBliss-6p34bwg. Both tweeters were used with the WG104-34/8 waveguide, while the low-frequency driver was the Purifi PTT6.5X08-NFA-06 midwoofer.

The new T34T-4 inherits the signature sonic character of the BlieSMa T34 family: outstanding resolution, exceptional transient speed, and an open, effortless, crystal-clear presentation with a touch of dryness yet plenty of air. This comes as no surprise, since all T34 tweeters share the same motor and mechanical design, differing only in diaphragm material. The subtle differences in sonic character stem directly from the unique properties of those materials.

A TeXtreme® diaphragm is physically stiffer than silk, yet not as rigid as beryllium. Consequently, the T34T-4 occupies the sonic middle ground between the T34S-4 and the T34B-4. Its higher stiffness allows it to reproduce brass instruments, drums, and percussion in general with greater realism and precision than silk. Beryllium, however, still pushes these qualities a step further, sounding more vivid, brighter, and more incisive. On the other hand, the T34T-4 renders vocals and bowed string instruments with greater smoothness, delicacy, and velvety texture than the beryllium version. In my experience, all TeXtreme® drivers -from woofers to tweeters - share a distinctive family character: a unique blend of rigidity, moderate brilliance, and a warm, velvety presentation of strings, wind instruments, and vocals.

Another subtle observation was that the loudspeakers equipped with the T34T-4 created a slightly deeper soundstage and a slightly stronger sense of tactile presence. The emphasis is on slightly - the difference is subtle, but nevertheless  audible.

The tweeter is remarkably versatile and equally convincing with virtually every musical genre. As for audible nonlinear distortion, there is simply nothing to report - it remains completely inaudible, regardless of listening level.

To summarize, the T34T-4 is an ideal choice for listeners who appreciate more attack and precision than silk tweeters typically offer, yet find metal domes too bright or too aggressive due to their extreme stiffness and lower intrinsic damping. A TeXtreme® diaphragm strikes an exceptionally well-balanced compromise - neither too soft nor too hard, but right in the sweet spot.

  "How to use" recommendations

The T34T-4 possesses a combination of characteristics that makes it an exceptionally versatile tweeter:

• Its large diaphragm, with an effective radiating area of 10.5 cm², combined with a ±1.5 mm linear excursion, provides substantial volume displacement and, consequently, very high acoustic output at the lower end of its operating range
• Its high sensitivity significantly reduces the required amplifier power, helping to minimize thermal compression
• The combination of large linear excursion and high power handling makes the tweeter particularly well suited for first-order crossover networks
• Despite its large diaphragm, the flush-mounted surround design provides remarkably wide dispersion. Wide dispersion can be a valuable asset in loudspeaker designs aimed at producing a more spacious and airy presentation. If narrower directivity is desired, it can easily be achieved with a waveguide; increasing dispersion, on the other hand, is far more difficult

Based on the measurement results, I can confidently recommend the T34T-4 for use in high-end multi-way loudspeakers.

In small listening rooms (up to approximately 20 m²), and in moderate-output two-way designs where the widest possible dispersion is desired, the tweeter can be crossed over as low as 1 kHz with a first-order high-pass filter. Admittedly, this is pushing the limits - but it is entirely feasible.

For small to medium-sized rooms (up to approximately 40 m²), where the goal is not maximum output but rather a more focused and expressive presentation together with a smoother diffuse sound field -particularly important in acoustically live rooms without dedicated acoustic treatment - I would recommend crossing the tweeter from 2–2.5 kHz and higher in combination with a WG104-34/8 add-on waveguide. This approach provides more uniform radiated sound power at high frequencies, helps reduce the perception of sibilance caused by excessive acoustic power in the 3–6 kHz region, increases sensitivity at the lower end of the tweeter's operating range, and improves integration with larger midrange drivers.

Raising the crossover frequency above 2.5 kHz also makes the T34T-4 an excellent candidate for large WMTMW loudspeaker systems intended for very large listening spaces. For such applications, I strongly recommend pairing it with a large waveguide approximately 150–180 mm in diameter. This further increases acoustic output while providing even better directivity control in the critical 2–6 kHz region.

Loudspeakers based on this tweeter are exceptionally well suited for long, fatigue-free listening sessions and are capable of reproducing virtually any musical genre with equal confidence and enjoyment.

  What is the price and where to purchase it?

At the time of publication of this review, the T34T-4 is already available for purchase at a price starting from €389.60 per unit (excluding VAT). It can be obtained through official BlieSMa distributors listed on the company’s website at bliesma.de, as well as via the online store audio-hi.fi.

  Summary

The sixth element of the BlieSMa family - the T34T-4 dome tweeter with a TeXtreme® diaphragm - left an exceptionally positive impression, both through its sound quality and its objective measurement results, which closely match the published datasheet. It is a worthy addition to the T34 series. With its introduction, every BlieSMa driver family is now available with TPCD diaphragms. This opens up new possibilities for designing loudspeaker systems using only BlieSMa drivers with the same diaphragm material from woofer to tweeter. Such material consistency contributes to a more coherent, seamless, and tonally uniform presentation. I can confidently recommend the T34T-4 for the most demanding loudspeaker projects.

What I liked:

• Exceptionally flat and smooth frequency response up to 23 kHz
• High sensitivity - 97 dB/2.83 V*1 m
• Large linear excursion - 3 mm peak-to-peak
• Titanium voice-coil former
• Very low harmonic distortion above 3.3 kHz
• Wide dispersion
• Can be crossed over as low as 1 kHz
• Excellent build quality

What I didn't like - a noticeable rise in distortion in the 2.5–3.5 kHz region

More extended measurements can be found here

Yevgeniy Kozhushko/27.07.2026