BlieSMa T25T-6 1" TeXtreme dome tweeter review

  What and why am I testing?

TeXtreme is taking the world by storm! In the form of TPCD diaphragms for speakers, it has already made a name for itself in the world of audio and has been adopted by many well-known brands, including the German company BlieSMa, which has released a couple of midrange models based on them - the 3" M74T-6 and 7“ M142T-6 midrange speakers, and one 7” W137T-854 woofer.

And now, in July 2025, BlieSMa released its first tweeter with a 25 mm TPCD dome diaphragm, the T25T-6. This adds a very important missing element to the company's TeXtreme lineup, making it possible to build loudspeakers entirely on TPCD diaphragm speakers, from top to bottom. To logically complete the model range, it remains only to supplement it with the largest tweeter with a 34 mm diaphragm. Hopefully, this moment is not far off.

As you may have guessed, today we will be talking only about the new T25T-6 tweeter. This is the fifth tweeter in the company's 25 mm tweeter lineup, built on the same chassis as the previous ones (my review of the aluminum T25A-6, beryllium T25B-6, silk T25S-6, and diamond T25D-6 tweeters), which means that we are talking about a tweeter from the “State of Art” category with unique characteristics, namely an ultra-lightweight (for dome tweeters) moving system, a super-powerful motor with an induction in the magnetic gap of 2 Tesla, and a large linear excursion of 2 mm from peak to peak.

I really like that companies like BlieSMa, by using different diaphragm materials, provide the consumer with a wide range of flavors and aromas sonic signatures of their speakers, allowing for more precise customization of the sound of loudspeakers and potentially satisfying the tastes of a much wider range of audiophiles.

I would like to express my great gratitude to Stanislav Malikov, the developer and owner of BlieSMa, for providing me with tweeter samples for testing.

Here you can get familiar with the BlieSMa history.

  What did the manufacturer state?

A laconic datasheet containing all the technical specifications and parameters required by the loudspeaker designer.

Of the numerical parameters, it is especially worth noting the high magnetic induction in the magnetic gap - 2 Tesla, very low voice coil inductance - 0.008 mH, very low mass of the moving system - only 0.15 grams, and a huge linear excursion of the moving system - 2 mm from peak to peak. Very cool!

The drawing shows the tweeter with half of the protective grille, thus indicating that it can be supplied with or without the grille. The grille is held in place by the magnetic field of the motor, which is so strong that there is simply no need to glue it. In fact, it is removable, and this additional convenience allows you to experiment with custom waveguides.

  Visual inspection

The tweeters come in a matched pair.

• The packaging - a sturdy package made of durable glossy corrugated cardboard. The tweeters are secured inside by cardboard inserts with shaped cutouts. The front part of the tweeter is additionally protected by a transparent plastic cover.
• The quality of workmanship is top-notch. No traces of glue, scratches, dirt and dust, stains and dents on the diaphragm, chips, gaps and misalignments. Absolutely nothing to complain about
• The faceplate of 6 mm thick is made of solid aluminum with six recessed mounting holes, which is covered with micro-textured black semi-matte powder coating. A soft foam rubber gasket is glued to the back of the faceplate
• The back cover is made of solid aluminum about two millimeters thick. It is covered with microtextured black semi-matte powder coating. When tapped with a finger, it is completely inert
• The magnet - ring neodymium, very powerful
• The surround - a narrow fabric concave half-roll
• The diaphragm - a convex dome made of TeXtreme. I am so used to the standard “checkered” pattern of TPCD diaphragms that I was pleasantly surprised to see a completely uniform matte black diaphragm in the T25T-6 tweeter. In my opinion, it turned out very well.
  The profile of the 5 mm high dome diaphragm is absolutely identical to the profiles of the beryllium T25B-6 and diamond T25D-6 tweeters, which means that the WG104-XX/25 series waveguides can be used with the T25T-6 with the same success.
• The thick gold-plated terminals are absolutely firmly glued into the faceplate with epoxy glue. From personal experience, I believe that these are the most reliable terminals I have seen in tweeters. They can withstand multiple soldering with a powerful soldering iron
• The protective grille is made of steel with a smooth semi-matte powder coating and a high degree (apparently about 70%) of acoustic transparency

 

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

  Impedance frequency response

The diagrams below show, at different scales, the impedance frequency response:

The measured parameters are very close to the datasheet. The resonance frequency turned out to be slightly lower - 883.5 Hz versus the stated 940 Hz, which is even better.

What can be said about the impedance response as a whole? It is safe to say that we are looking at a perfect example of the impedance curve of a dome tweeter with a moving coil. I have yet to encounter better response. First, it is perfectly smooth across the entire frequency range, with not the slightest hint of any parasitic resonance phenomena in the moving system. The main resonance of the moving system at 883 Hz, of course, does not count. Second, the increase in impedance with increasing frequency is extremely low, which is due to the very low inductance of the voice coil (0.008 mH), achieved thanks to the small number of voice coil turns, the copper sleeve and the deeply magnetically saturated motor. This is a distinctive feature of a good motor and has a beneficial effect on reducing nonlinear distortion. The ratio of the maximum impedance modulus at 20 kHz to the minimum at 6 kHz is only 1.1 - I have only seen such a low value in BlieSMa T25 series tweeters.

The impedance frequency response tells us about a good motor and a well-balanced moving system.

  On-axis frequency response (at 315 mm)

Below are the smoothed axial frequency responses of two tweeters, measured in a test baffle at a distance of 315 mm from the microphone:

The frequency responses of both samples are identical up to 35 kHz. The measured sensitivity, according to my estimate, is about 91.5-92 dB, which is even slightly higher than the stated value of 91 dB. The shape of the frequency response is very close to the datasheet, with the only difference above 27 kHz, i.e., closer to the diaphragm's break-up mode.

The frequency response is close to perfect, I have no complaints about it. It is very even in the 2-10 kHz band and smooth across the entire frequency range up to 31 kHz. Between 10 and 30 kHz, there is a smooth decrease of up to 2 dB, caused by an increase in the inductance of the voice coil and the phase lag of the peripheral radiation of the diaphragm relative to the radiation of the dome center.

Above 31 kHz, the diaphragm enters a break-up mode, accompanied by frequency response spikes ranging from 6 to 9 dB. The quality factor of the resonance spikes appears to be low, so they should decay quickly.

  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 and up to 4 kHz, the frequency responses are stable and consistent, after which they begin to split and monotonically decline with an angle of deviation and frequency up to the diaphragm's break-up mode. The tweeter's sound dispersion is very wide, one of the widest I have encountered in 25 mm dome tweeters. Only the aluminum T25A-6 has a wider dispersion.

  Harmonic distortion (at 315 mm)

Above are the plots of 2nd to 5th harmonic distortion at voltage of 4 Volts, which corresponds to average sound pressure level of 94.5-95 dB. The measurements were taken on-axis at a distance of 315 mm to the measuring microphone. To limit the tweeter overload in terms of power and amplitude of diaphragm displacement when measuring harmonic distortion, a second-order digital high-pass filter with a cutoff frequency of 800 Hz was used, therefore, in these plots we analyze the frequency range only from 800 Hz and above.

The euphonious second harmonic clearly dominates in the entire range of operating frequencies. It reaches a minimum value in the interval of 2.5 - 7.5 kHz and increases at the edges of the frequency range. Higher order harmonics reach a minimum value in the band of 4 - 10 kHz. Below 4 kHz they monotonously grow with decreasing frequency.

Overall, the harmonic distortion frequency profile is completely identical to the T25 series tweeters (T25A-6, T25B-6, T25D-6, T25S-6), and I would rate overall distortion level as "very low" above 2.5 kHz.

  Voice coil current harmonic distortion

This type of measurement, despite its simplicity, is an excellent tool for assessing the linearity of a speaker motor. The above plots show the frequency dependences of the 2nd, 3rd, 4th and 5th harmonics of the voice coil current at 4 Volts.

Voice coil current nonlinearity is the direct nonlinearity of the mechanical force driving the speaker cone, since this force is related to the current by a simple relationship F=B*L*I, where B is the magnetic field strength, L is the length of the voice coil wire inside the magnetic gap and I is the current. So, in principle, it is practically impossible to obtain sound pressure distortion lower than current distortion in the frequency range where the contribution of the motional nonlinearity becomes insignificant.

The entire frequency range (> 700 Hz) is dominated by the euphonious second harmonic. The harmonics of all orders show a monotonous increase with decreasing frequency, starting from about 4 kHz.

The increase of the 3rd harmonic above 5 kHz is not due to the tweeter, but to the limitations of my measuring setup. The level of the remaining harmonics is extremely low.

I would rate the level of current harmonics of all orders as "very low" in the range above 2.5 kHz.

  Step response

The step response demonstrates excellent rise time and fast decay. The tweeter settles down quite quickly, though not aperiodically, but by crossing the rest line once - a characteristic behavior of a second-order oscillatory system. The small "teeth" are due to the first resonance of the diaphragm at 32 kHz.

  Waterfall

The waterfall type of measurements is another way to investigate the linear response of a system, allowing us to better identify any hidden resonances that are difficult to discern in other types of measurements:

In the range up to 30 kHz, the waterfall is practically perfect, fading very quickly and leaving nothing after the second slice. As expected, diaphragm resonances in the break-up mode above 30 kHz have low quality factor, so they die away quite quickly.

A slight dip in the 2-5 kHz range is due to parasitic reflections from the edge of the test baffle and is not related to the actual behavior of the tweeter. This effect is more pronounced the wider the dispersion of the tweeter.

  Listening impressions

As usual, after completing objective measurements, the microphone passes the baton to the ears. This time, in addition to listening “in my hands,” I was able to conduct a full evaluation of the tweeter in real conditions in the miniature two-way PuriBliss-4p25b loudspeakers and compare its sound with the versions using the silk dome BlieSMa T25S-6 and beryllium dome T25B-6 tweeters.

The new T25T-6 tweeter has retained the main BlieSMa's T25 family distinctive features: highest sound resolution, excellent speed (attack), and a very light, open, clean, a bit dry but very airy sound. The nuances in the differences stem from the characteristic features of the diaphragm material. The TeXtreme diaphragm is physically harder (stiffer) than silk and softer than beryllium diaphragms. Therefore, the sound character of the T25T-6 is between that of the T25S-6 and T25B-6. No, not exactly in the middle, but rather in the half closer to silk. Due to its greater hardness, it is better than silk for brass wind instruments and any percussion instruments, but beryllium is even more realistic here - more sparkling, brighter, and sharper. On the other hand, the T25T-6 conveys vocal nuances and stringed bowed instruments more softly, delicately, and velvety than beryllium. In general, all speakers with TeXtreme diaphragms (from woofers to tweeters) have their own characteristic, one might say "generic" coloring, manifested in a combination of hardness, moderate brightness and a special warm velvety sound in bowed strings, all wind instruments and vocals.

The tweeter is extremely versatile and omnivorous, capable of handling absolutely any musical genre. Audible nonlinear distortions are not even worth mentioning, as they are completely absent at any volume.

The T25T-6 will be the perfect choice for those who have not found happiness among silk dome tweeters due to their insufficient rigidity and "smearing" of the sound attack to one degree or another, and also could not get along with metal dome tweeters due to their tendency to brightness and ringing due to high rigidity and insufficient internal damping of the diaphragms. TeXtreme is moderately soft and moderately hard - the golden mean!

Below are pictures of three versions of the PuriBliss-4p25 loudspeaker with the TeXtreme T25T-6, beryllium T25B-6 and silk T25S-6 tweeters:

  "How to use" recommendations

Very low distortion opens the door for the T25T-6 to be used in any high-quality home audio system with two or more frequency bands down to 2 kHz. The wide sound dispersion contributes to the most spacious sound possible, which is "detached" from the loudspeakers and has a lot of “air.” With its shallow mounting depth and small 68 mm diameter flange, this speaker is ideal for car audio systems!

If you need to get a more engaging and focused sound, provide a more uniform diffuse sound field, which is especially important in acoustically "live" rooms without special acoustic treatment, I would recommend using the tweeter in combination with waveguides of the WG104-XX/25 or WG150-11 series. This will allow you to achieve a more uniform radiation of sound power at high frequencies and get rid of sibilance associated with excess sound power in the range of 3-6 kHz, increase the output at the bottom of the tweeter's operating frequency range and improve its coherence with a large diaphragm midrange speaker.

  What is the price and where to purchase it?

At the time of publication of this review, the T25T-6 tweeter is already available for purchase at a price starting at €240 per unit, excluding VAT. It can be purchased from official BlieSMa distributors listed on the company's website, bliesma.de.​

  Summary

The first TeXtreme tweeter from BlieSMa made a very pleasant impression with its sound and objective measurements, which are well consistent with the datasheet. It is a worthy addition to the T25-6 tweeter lineup. With its release, it is finally possible to build a three-way loudspeaker entirely from BlieSMa drivers with the same diaphragm material in all frequency bands, which contributes to the overall integrity and uniformity of the sound. Frankly speaking, I see no drawbacks in the T25T-6 and can confidently recommend it for the most serious projects!

So, what I liked:

• Very smooth and even frequency response up to 31 kHz
• Good sensitivity - 91 dB/2.83 Volt*1 meter (at 6 Ohm impedance!)
• High linear excursion - 2 mm from peak to peak
• Titanium voice coil former
• Very low harmonic distortion down to 2.5 kHz
• Very wide sound dispersion
• Excellent workmanship
• Compact size
• Can be used down to 2 kHz (without a waveguide)

What I didn't like - a rare case where there's nothing to complain about

More extended measurements can be found here

Yevgeniy Kozhushko/03.09.2025