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BlieSMa T25A-6, T25B-6, T25D-6, T25S-6 - a comparison of dome materials

ctrl

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#21
The listening test of the Be version is very clear about sibilants:
"otherwise there may appear problems with a sharp transmission of sibilant sounds "
On that point, Be is better than aluminium but not as good as silk.
Well, listening tests without exact specification of initial conditions or measurements, we only know that the woofer was "mated with a tweeter at 2.5 kHz by fourth-order acoustic filtering", should always be treated with caution.

If the 6-8kHz range was slightly lowered in one tweeter, or if this range was neutral or slightly raised in the other (compared to the average sound pressure level), then it would already explain the different listening impressions.
In addition, the silk dome emits much less "sound power" at 8kHz than the Al-dome, as can be seen in post#11.

This is less a question of tweeter quality, but rather a question of crossover tuning. Which is also said in the review:
...carefully handle the formation of the frequency response in a certain range, otherwise there may appear problems with a sharp transmission of sibilant sounds.
 
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#23
The listening test of the Be version is very clear about sibilants:
"otherwise there may appear problems with a sharp transmission of sibilant sounds "
On that point, Be is better than aluminium but not as good as silk.
I bet most people would prefer the damn silk dome in an ABX test.
 
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#24
All you're seeing in those step responses is the magnitude and Q of the break-up mode.
That is clearly one of the main differences between the different tweeter materials that this test (step response) brings out. It's quite good also to demonstrate that the underlying step responses are more or less identical, once the break-up mode is removed.
Since in all cases other than silk this is well above the range of frequencies we can hear, the comparison is misleading.
How is it misleading? It seems to be quite informative overall, particularly if one hasn't had the opportunity to see this sort of comparison elsewhere.
...overlaying step responses of these tweeters with no other information about their performance is the wrong way to compare them.
The step response may be a limited sort of test signal, but why is it wrong to compare the tweeters by using it? Would a square wave be better?
 
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#25
If the 6-8kHz range was slightly lowered in one tweeter, or if this range was neutral or slightly raised in the other (compared to the average sound pressure level), then it would already explain the different listening impressions. In addition, the silk dome emits much less "sound power" at 8 kHz than the Al-dome...
Based on this observation, the listening tests to try and discern the benefits between different tweeter materials appear to be inherently flawed. Much of what is heard is merely frequency response differences.

What is actually needed is high-resolution equalisation of the on-axis frequency response of each tweeter, so at least they are flat on axis to within 0.1 dB or better. Then it may be possible to conduct a listening test to see if the materials do indeed make a large differences. Using inverse FIR filters to accomplish this sort of equalisation can be done these days.

Of course, some tweeters may have higher levels of harmonic distortion, which could also affect the results of the listening tests. Harmonic distortion levels could be measured to make sure that substandard designs are removed prior to any listening tests.
 

andreasmaaan

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#26
How is it misleading? It seems to be quite informative overall, particularly if one hasn't had the opportunity to see this sort of comparison elsewhere.
The step response may be a limited sort of test signal, but why is it wrong to compare the tweeters by using it? Would a square wave be better?
Misleading because it tends to lead to comments like some of those in this thread (e.g. #3, #15, #22) in which people look at the step responses under the presumption that smoother = better.

Square waves would be no better IMO, no. The most useful comparative measurements can generally be found in HifiCompass’ individual reviews: frequency response, polar response, CSD, nonlinear distortion (IMD would be more useful than HD but IIRC HifiCompass does not measure it with tweeters).
 
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headshake

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Thread Starter #27
I fully agree that the Be tweeter needs a careful listening test as it is the best candidate to replace the Silk tweeter.
I am interested in comparing the Silk to the Be once it comes out. I can say that I have yet to find the t25b-6 sibilant.


...

Material love side note:

The speed of sound through beryllium is nearly 2.5 times faster than that of aluminum or titanium
"https://www.vueaudio.com/beryllium/the-use-of-beryllium-in-transducer"

https://www.engineeringtoolbox.com/sound-speed-solids-d_713.html

Diamond should be even faster.
 
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headshake

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Thread Starter #29
the price for diamond products is unconscionable. Eventually it will be less expensive than Beryllium because they are making it to use as chip substrates. It is already very mass produced.
One would expect that- but I also don't know what it takes to make a diamond tweeter. I know I can get sacks of synthetic diamond out of china for cheap.

The price listed in the hificompass review of the prototypes does not quite match reality. Things are already a little cheaper.

If the diamond is less than a grand/pr I might go for it. No f'n way at $4000/pr.

https://audio-hi.fi/en/bliesma-m-33.html

https://solen.ca/?s=bliesma
 

gene_stl

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#30
Parts Express lists sapphire dome tweeters for about $60. Synthetic sapphire has been made on an industrial scale for well over one hundred years.
Synthetic diamond for much less time but still several decades.

In the case of sapphire it is not clear whether it is single crystal or polycrystalline. The diamond diaphragms are likely to be polycrystalline. Making diaphragms out of them is , just a marketing gimmick. Ceramics and composites probably can perform as well.
 

valerianf

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#31
There is also on the web an Audax dome tweeter Gold plated for $105.
Stratospheric price for the dome tweeter diamond "durst" treated has no real justification.
The silk dome tweeter is not so far in performance at a fair price, and the Be plated is available as a cheap exotic choice.
 

muad

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#32
There is also on the web an Audax dome tweeter Gold plated for $105.
Stratospheric price for the dome tweeter diamond "durst" treated has no real justification.
The silk dome tweeter is not so far in performance at a fair price, and the Be plated is available as a cheap exotic choice.
I don't think it's plated. Pretty sure it's solid beryllium all the way through.

This stuff is like hifi in general... Diminishing returns. The differences are measurable, but questionably audible. And if you can hear the difference, it doesn't mean it sounds better.

I'm using beryllium and its smoother than most tweeters that I've come across. I think at this level it's mostly implementation.
 
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#33
Parts Express lists sapphire dome tweeters for about $60.
Those tweeters seem to have quite good performance, with a flat and extended frequency response. However, they still display a very large, lightly-damped, high-frequency resonance peak.

For comparison, here are some indicative values of the Modulus of Elasticity (E) for a few different materials used in loudspeaker diaphragms. Kates (1981) mentioned that desirable properties of materials for loudspeaker diaphragms are high specific elastic modulus (E/rho, rho=density of the material), large flexural rigidity and large internal loss (tan delta, where the value of tan delta quantifies the way in which a particular material absorbs and dissipates energy).
Code:
----------------------------------------
                  MODULUS OF
MATERIAL          ELASTICITY   TAN DELTA
----------------------------------------
Diamond            1050 GPa     0.0001
Alumina Ceramic     393 GPa     0.01
Sapphire            343 GPa     0.0001
Beryllium           287 GPa     0.005
Titanium            106 GPa     0.002
Kevlar               76 GPa     0.03
Carbon fibre         70 GPa     0.02
Aluminum             68 GPa     0.002
Magnesium            44 GPa     0.006
Paper               2.5 GPa     0.03
Polypropylene       1.3 GPa     0.06
----------------------------------------
 
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valerianf

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#34
Need to add one more material:
Titanium 104 GPa

There is some good tweeter that is using a titanium base material with success.
 
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Mashcky

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#36
I ordered the T25A from Solen when they were on sale during the holiday. The build quality is impressive. Nice heavy aluminum housing and faceplate. Grill looks nice too.

I’m not sure what I’ll use them for yet. Probably a three-way tower with waveguide in the future.
 
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