Strange thing happened with Bliesma T34A

[superlian]

Does someone have a idea of what happened here?

It could be a children but the mesh is very fine/narrow and the problem is 100% equal on both.

 

[mondogenerator]

Possibly over excursion of the dome?
Just guessing.

 

[kceenav]

^this. Although the amount of damage - deepness of the dents - would be surprising to me. So, might be that someone (...) poked through the mesh with something thin.

 

[stv]

Possibly over excursion of the dome?

I doubt that the force of a tweeter voice coil could result in such a huge damage (supposedly leaving the magnet gap).
also, i suppose the susupension would limit the max excursion long before the dome hits the grille...

 

[mondogenerator]

I doubt that the force of a tweeter voice coil could result in such a huge damage (supposedly leaving the magnet gap).
also, i suppose the susupension would limit the max excursion long before the dome hits the grille...

That's a good critique of my reply.

I notice you haven't contributed anything to the OP at all.

Do you have an opinion on how the damage was caused?

Or you just like to put down others responses?

 

[tmuikku]

If it means anything my Jordan JX92s fullrange drivers developed few kinks, on both drivers. I attributed to children damaging them until I noticed fresh wrinkle with no kids around. The cone damaged due to listening too loud! Some breakup or bottoming of suspension or something makes so much force a wrinkle appears, at least that is the most reasonable explanation I could come up with at the time. Perhaps there is some tension on the material which fails with a enough resonance and deformation happens. Perhaps this can happen to a dome as well.

Did you have a party? If not, check the amplifier output with scope, just in case, before rolling in another pair Music doesn't usually contain mucho highs but distortion does! Or the amplifier could have some oscillation why not.

Keep feeding energy to resonance and things break

 

[stv]

That's a good critique of my reply.

sorry about that, mondogenerator, i did not mean to be rude. I should stop posting without enough time to think ...

superlian, one possible other cause might be a sudden air pressure increase, such as opening a air tight enclosure after a long air transport?

edit: i should add that i once damaged my seas alu dome tweeters when measuring the distance to the microphone with a pointed ruler. i got similar measurement results to yours. I was able to "repair" the domes by carefully pressing the domes into shape after removing the diaphragm construction from the magnet. the strong resonance of the indentation disappeared, but I suspect the 15 kHz resonance will remain (see picture).

 

[Bill poster]

The shape of creases seem to follow the grill pattern

 

[superlian]

The owner og the tweeters tells me that he was trying it close to the dustcap to TAD1201 (>10 kg magnet) as a coax. He used som steel wire to keep it in place i think. Could the magnet force from TAD1201 pull the voicecoil and dome like a spring and then release it so it collided with the grill?


https://audio-database.com/PIONEER-EXCLUSIVE/unit/tm-1201-e.html

 

[Pilover2000]

The shape of creases seem to follow the grill pattern

If that is true might a crossover change be good advice ?

 

[stv]

Could the magnet force from TAD1201 pull the voicecoil and dome like a spring and then release it so it collided with the grill?

the voice coil and dome are non magnetic (if no current flows), but maybe the grilles themselves are magnetic and could have been deformed to crush the domes?

 

[Bergfinn]

...but maybe the grilles themselves are magnetic and could have been deformed to crush the domes?

No, the grills has not been deformed.
Maybe the damage is because I didn't use protecting caps?
I am the owner of the tweeters.

I use T34B now, and YES, I use protecting caps on them.

 

[superlian]

Ok. Lets go

 

[TNT]

Where is your XO and how steep?

//

 

[superlian]

No 1:

A little bit of tape-glue on the fingertip to pull out the dent careful.

Its i tiny hair crack in the dome.

 

[superlian]

No2:
The damage is very sharp.

 

[superlian]

Bergfinn told me that T34b in comparison sounds signifcant better.

I think t34a should sound almost as good as the beryllium version. The beryllium version should only have a small touch of «silk oil» in adittion.

I have earlier tested Seas DXT vs T34b and DXT didnt sound bad in comparison.

My conclusion is that Bergfinn heard the distortion from the dents in T34a and that they therefore sounded like 15 USD metal dome tweeters.

 

[superlian]

I have reconed a pair of Focal Titanium tweeters before.

Maybee i can get new domes from Bliesma and give it a try?

 

[superlian]

Now i got answer on mail from Bliesma. Great service

The cause must be a low frequency signal.
It wasnt used protection capasitor with active crossover.

It is possible to recone them and that will incl freight and VAT cost nearly 50% of new tweeters but its worth it.

 

[daqvin_carter]

Always use a capacitor to protect the tweeter even if you swear you do not need it.
Nothing like power blips to cause LF to sneak into the output.
No good hearing a compression driver slap around when the power flickers and you know those drivers are likely dead now.