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Multi-Way Conventional loudspeakers with crossovers

Beryllium fatigue
Beryllium fatigue
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Old 7th August 2018, 11:55 AM   #1
Joshcpct is online now Joshcpct  Germany
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Location: near luxembourg
Question Beryllium fatigue

Hi folk

Insiders fear the TAD diaphragm crackin

How to detect this?
Some write about rings (assume in shape of the phaseplug?) and to hold the Dia against light (i assume rings appear illuminated then??) for check.

However, just found ET703 dia on ebay with those "signs" of scratches:
Click the image to open in full size.
If you look close, one corner has bright, another dark scratches.
They look like finger nail scratches but.... is that the beryl fatigue sign?

Does such driver necessarily crack soon?
Does it distort when sweeping now like that?
Has anyone tried to rescue such condition by coating (e.g. aquaplas paint film applied on inside) ??

cheers
Josh
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Old 7th August 2018, 12:48 PM   #2
lowmass is offline lowmass  United States
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I do not have direct experience with this driver but those really dont look like cracks to me.

I do have some experience with Be domes ( not loudspeaker related). Last time we tryed to "clean" one using acetone then rinse in de ionised water with an alcohol rinse. We got some markings that looked like your darker "scratches".

We have seen lighter "scratches" similar to yours from rubbing surface

Cannot say for sure but like said we have seen similar markings that have nothing to do with cracks. Best of course to get some input from someone who has direct experience.
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Old 7th August 2018, 07:01 PM   #3
Joshcpct is online now Joshcpct  Germany
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Hi lowmass. Thx for sharing your experience! Thats calming in a way! How thick are your domes/materials?

Come on, any TAD users here? Raise the voice
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Old 7th August 2018, 10:58 PM   #4
TBTL is offline TBTL  Germany
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Does it have ferrofluid?
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Old 8th August 2018, 01:43 PM   #5
lowmass is offline lowmass  United States
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Quote:
Originally Posted by Joshcpct View Post
Hi lowmass. Thx for sharing your experience! Thats calming in a way! How thick are your domes/materials?
The domes we had made were about 1/2 mm thick and 75 mm diam.

They were used in a small vacuum furnace for X Ray diffraction study. The domes are transparent to X rays so they make a good "window" to shoot that light through.

We got oil on some of them and needed to clean off. Its very difficult to clean and it stains easily and due to the "flat" finish every thing you touch it with can leave a noticeable mark.
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Old 8th August 2018, 03:16 PM   #6
Joshcpct is online now Joshcpct  Germany
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@lowmass
Interesting. U wear gloves? Toxic? Careful touching or is it quiet flexible material?
I know for speakers 1000th inch thickness is normal, so bit less. But someone told me beryl domes arent as sensitive as everyone sais and they probab crack when u hammer them against the phaseplug with moronic first order hipass
Otherwise that guy said it was possible to press and slightly deform with the finger and it came back.
Confusing story. Hows ur experience??

@TBTL : ferrofluid isnt used on hi quality horn drivers. So beryl and FF dont meet normally
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Old 8th August 2018, 04:17 PM   #7
hottattoo is offline hottattoo  United States
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https://materion.com/products/beryll...agm-assemblies

You can get excellent performance from these diaphragms by replacing the Jbl 2441 and similar drivers aluminum diaphragms. These have a PEEK surround to prevent cracking / failure. Beryllium is lighter and stiffer than any metal used in speaker drivers. It is toxic, so I would wear gloves when handling an a mask if particles / dust are airborne.
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Old 8th August 2018, 05:28 PM   #8
lowmass is offline lowmass  United States
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I wore gloves BUT not because its toxic. It was just to keep contaminants off Be domes that were 10K $ each !!

Be in solid form is not a problem. Its when you grind/ sand into dust, and or heat to a vapor that its trouble.

Its also quite strong and makes great springs. My motocross bike has Be shock spring. The domes we had were very rugged at 1/2 mm thick and I suspect the much thinner domes in loudspeakers are more durable than most would think so handle with care BUT don't worry bout it
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Old 9th August 2018, 03:39 AM   #9
ScottG is offline ScottG  United States
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-it looks like the brushed-on glue for the VC as it ages.
__________________
perspective is everything
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Old 9th August 2018, 03:23 PM   #10
Joshcpct is online now Joshcpct  Germany
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Quote:
Originally Posted by ScottG View Post
-it looks like the brushed-on glue for the VC as it ages.
Ya you made me thinking just now: ive seen that orbital shadow on other beryl domes. Just not all the way around but bit here bit there...

Also part of fatigue?

So little reply. I start believing not many have ever had beryl in this forum. The few that have are rare and may ignore whats happening inside...
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