Strange rattling noise from woofer |
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Jo bg
Young Croc Joined: 08 March 2017 Status: Offline Points: 552 |
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Posted: 29 July 2021 at 10:13am |
Hi
Anyone knows what this noise could be? B&c 18 sw115-4 ohm , has been spanked hard in a th118 for 5 years, so we can say it did it's job, but still I would like to know what's up, second driver developing this issue in a th118. No voicecoil rubbing, everything moves right without frictions, there is just this high pitched metallic rattling that rises with level . They are going in for a recone next week, but still don't knowing what is happening drives me mad. If someone can enlighten me I would be grateful! Video of driver making such noise |
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Jo bg
Young Croc Joined: 08 March 2017 Status: Offline Points: 552 |
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Ps it's not the grille...
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kedwardsleisure
Old Croc Joined: 20 January 2009 Location: Staffordshire Status: Offline Points: 4938 |
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have you checked for tiny tears in the surround/suspension? Dust cap glued all around?
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Kevin
North Staffordshire |
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Jo bg
Young Croc Joined: 08 March 2017 Status: Offline Points: 552 |
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Thanks for the hints, I will check this evening!
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Earplug
Old Croc Joined: 03 January 2012 Location: Europe Status: Offline Points: 7199 |
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Have you tried "tapping" around the cone? There might not be any rubbing, but a loose winding on the coil that might be heard if you hit the cone at different points around the thing close to the center/coil. Edited by Earplug - 30 July 2021 at 5:43am |
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Earplugs Are For Wimps!
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Tinnitus Rex
Registered User Joined: 31 October 2020 Status: Offline Points: 274 |
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Have a close look at the spider suspension to see if has detached from the voice coil stem underneath the cone , pushing the cone full forward usually reveals this .if it has this can be fixed.a stitch in time saves a recone
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"couldn't we just like... use headphones?"
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Peter Jan
Young Croc Joined: 16 December 2008 Location: Belgium Status: Offline Points: 1019 |
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Check if the spider is still properly glued to the chassis.
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Wikl109
Young Croc Joined: 29 April 2009 Location: Yorkshire Status: Offline Points: 968 |
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I'd say this is a good shout. I had one of the bass drivers on my home system develop a problem exactly like this some years back. No rubbing when pushing the cone and it played fine at a low volume. However when turning the system up and play anything with really deep rumbling bass there was a slight high frequency rattle from the drive unit. I could only come to the conclusion the winding on the former had come loose. It was replaced under warranty as it was a manufacturing fault. |
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Cheers, Chris.
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Tinnitus Rex
Registered User Joined: 31 October 2020 Status: Offline Points: 274 |
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This is exciting,when are you drawing the result? I bet 90dB on the spider and 50 on the surround
Edited by Tinnitus Rex - 30 July 2021 at 2:08pm |
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"couldn't we just like... use headphones?"
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APW
Young Croc Joined: 13 November 2012 Location: Kent, UK Status: Offline Points: 1173 |
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I'd put money on the bottom few turns of the coil have broken loose (come off the coil former), seen it a few times on customers kit when the coil assembly has clouted the motor backplate... normally due to lack of or incorrectly set HPF. |
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smitske96
Young Croc Joined: 16 February 2016 Location: The Netherlands Status: Offline Points: 1085 |
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@APW
The 18SW series should not get damaged that way. Excursion is eventually limited by the suspension and can't reach Xdamage.
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Wikl109
Young Croc Joined: 29 April 2009 Location: Yorkshire Status: Offline Points: 968 |
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In my case it was clearly a manufacturing fault and not caused by over excursion. Rather annoyingly the other bass driver in the other speaker developed the same fault a couple of years later.
By that time it was out of warranty and I had to fork out £100 for a new 8" bass driver to be shipped over from America. Both replacement drivers have been playing fine for 10 years plus now so it was probably a problem with the adhesive being used at the time of original manufacture on that batch. I still have the second faulty unit here somewhere. It could be one of a number of things that's caused Jo bg's problem but I think a loose winding from the coil is quite possible. |
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Cheers, Chris.
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