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Multi-Way Conventional loudspeakers with crossovers

spots at the back of a woofer paper cone?
spots at the back of a woofer paper cone?
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Old 12th September 2019, 05:39 PM   #1
daemonsgr is online now daemonsgr  United Kingdom
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Default spots at the back of a woofer paper cone?

Hi,

One of the JBL woofers has some extra material on the back of the paper cone.
Is this common or a manufacturing problem?
I can send it back if needed.

Thanks
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Old 12th September 2019, 06:12 PM   #2
Galu is offline Galu  Scotland
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I would regard this as normal and part of the coating process applied to the rear of the cone.

This old Bose woofer coating looks even lumpier. Perhaps it helps break up cone resonances!
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Old 12th September 2019, 07:25 PM   #3
daemonsgr is online now daemonsgr  United Kingdom
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Quote:
Originally Posted by Galu View Post
I would regard this as normal and part of the coating process applied to the rear of the cone.

This old Bose woofer coating looks even lumpier. Perhaps it helps break up cone resonances!
Thanks a lot!!
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Old 12th September 2019, 07:33 PM   #4
Galu is offline Galu  Scotland
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You're most welcome. Maybe they were scraping the bottom of their 'paint' pot!

I certainly wouldn't go to the trouble of returning the driver - more chance of heavy drivers being compromised through transit damage.
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Old 12th September 2019, 08:19 PM   #5
phase_accurate is offline phase_accurate
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All my JBLs (2206 and 2226) have that as well and also my Beyma 15LX60v2s (of which I suspect, that they have cones from the same manufacturer).
I would say that this is coming from the process used to manufacture these cones. They are not made by cupping some wet sheets of paper into shape but rather by a process like the one that is used for hand paper making with a paper/glassfiber slurry and a fine mesh. Maybe someone whose mother-tongue is english might properly describe it. But you can rest assured that it is basically a sign of quality.

Regards

Charles
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Old 12th September 2019, 09:12 PM   #6
Galu is offline Galu  Scotland
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I understand what you mean Charles.

Here's everything one needs to know about the speaker cone manufacturing process!

https://www.pearl-hifi.com/06_Lit_Ar...e_Tutorial.pdf
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Old 12th September 2019, 09:46 PM   #7
daemonsgr is online now daemonsgr  United Kingdom
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Quote:
Originally Posted by Galu View Post
You're most welcome. Maybe they were scraping the bottom of their 'paint' pot!

I certainly wouldn't go to the trouble of returning the driver - more chance of heavy drivers being compromised through transit damage.

no no! they sound super nice and I waited 2+ months for them!
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Old 12th September 2019, 10:19 PM   #8
simoon is offline simoon  United States
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Those are a completely normal part of the cone making process.

Some driver companies purposely do similar things to help with rigidity and resonance control.

Just take a look at the highly regarded SB Acoustics Satori papyrus mid.

Click the image to open in full size.
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