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Buzz but not delamination?

65.240.194.62

Posted on May 7, 2021 at 07:05:45

ketchup
Audiophile

Posts: 621
Location: Pennsylvania
Joined: February 29, 2004

My 3.6Rs have a slight buzz on some bassy tracks, and I discovered that if I walk behind the speaker and press on the horizontal steel pieces under the socks it goes away (I'm pressing the steel pieces forward, toward the front of the speaker).

I assume that this means it's not the voicecoil pulling away from the mylar. Is that true? If so, what is actually causing this buzz and how do you fix it? Is it the bar vibrating against the perforated steel? If so, that seems like an easy fix. I can either put something between the bar and perforated plate to stop the motion or glue them together. Or could it be the bar rattling against the frame where it attaches? Could it have come loose?

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RE: Buzz but not delamination?

Norman M

09:25:43 05/08/21

3M fastbond 30 NF

emailtim

09:47:08 05/08/21

RE: Yes, I would say the bar (or several) has become unstuck. ...

andyr

17:40:08 05/07/21

...

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RE: Buzz but not delamination?

Norman M

09:25:43 05/08/21

3M fastbond 30 NF

emailtim

09:47:08 05/08/21

RE: Yes, I would say the bar (or several) has become unstuck. ...

andyr

17:40:08 05/07/21

RE: Yes, I would say the bar (or several) has become unstuck. ...

ketchup

18:04:41 05/07/21

RE: Yes, I would say the bar (or several) has become unstuck. ...

shumi

04:27:02 05/08/21

RE: "The plant uses 3M fastbond 30 NF to glue the bars...do not use too much." ...

andyr

05:40:32 05/08/21

RE: "Was it just the ends of your bars that became loose " ...

andyr

18:07:38 05/07/21

RE: "Was it just the ends of your bars that became loose " ...

Roger Gustavsson

02:54:53 05/08/21

RE: "These can come lose, it is just a screw." ...

andyr

05:43:26 05/08/21

from the factory

Roger Gustavsson

05:52:34 05/08/21

What is the red goop in the tube ???

emailtim

09:44:52 05/08/21

RE: What is the red goop in the tube ???

ketchup

11:17:41 05/08/21

RE: What is the red goop in the tube ???

pictureguy

22:30:40 05/08/21

RE: What is the red goop in the tube ???

Norman M

10:16:47 05/09/21

RE: What is the red goop in the tube ???

pictureguy

10:44:23 05/09/21

RE: What is the red goop in the tube ???

Roger Gustavsson

01:46:01 05/09/21

Wow, it's amazing that those,..

DustyC

08:07:12 05/08/21

RE: Yes, I would say the bar (or several) has become unstuck. ..., posted on May 7, 2021 at 17:40:08

andyr
Manufacturer

Posts: 12548
Location: Melbourne
Joined: September 2, 2000

This happened to my IIIAs, many years ago.

Given the glue failed once ... I didn't want it to fail again. So I drilled a hole through each end of each bar - and through the metal driver-surround - and used 4mm (5/32", in your language!) bolts with a spring-washer, to clamp the bars tight, permanently.

Mind you, if you do this, you need to tape A3 sheets of paper both sides of the driver, to stop drill-scarf from getting onto the mylar or into the holes.

Andy

RE: Yes, I would say the bar (or several) has become unstuck. ..., posted on May 7, 2021 at 18:04:41
ketchup Audiophile Posts: 621 Location: Pennsylvania Joined: February 29, 2004	Thanks! What glue are you talking about that failed? Was it just the ends of your bars that became loose and screwing them back down corrected the problem?

RE: "Was it just the ends of your bars that became loose " ..., posted on May 7, 2021 at 18:07:38
andyr Manufacturer Posts: 12548 Location: Melbourne Joined: September 2, 2000	Yes - and as there were no mechanical fixings that I could see, I assumed Magnepan must've used glue, originally. Screwing the bars down ... stopped them vibrating. :-)) Andy

RE: "Was it just the ends of your bars that became loose " ..., posted on May 8, 2021 at 02:54:53

Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010

I have some humps in the response of my 3.6 (80-90 Hz). I have located it to the two buttons on top of the bass driver holding the Mylar to the backplate. These can come lose, it is just a screw. Mine are still not buzzing but I have a PEQ cutting out the resonances right now. I am too lazy stripping them down right now.

The crossbars on the perforated sheet steel are glued and can come lose. My old Tympanis (-76/77) have them glued and screwed.

RE: Yes, I would say the bar (or several) has become unstuck. ..., posted on May 8, 2021 at 04:27:02
shumi Audiophile Posts: 155 Location: Virginia Joined: January 11, 2020	The plant uses 3M fastbond 30 NF to glue the bars...do not use too much.

RE: "The plant uses 3M fastbond 30 NF to glue the bars...do not use too much." ..., posted on May 8, 2021 at 05:40:32
andyr Manufacturer Posts: 12548 Location: Melbourne Joined: September 2, 2000	So if it fails after a number of years ... why would you simply want to use the same glue, to repair the failure? Andy

RE: "These can come lose, it is just a screw." ..., posted on May 8, 2021 at 05:43:26
andyr Manufacturer Posts: 12548 Location: Melbourne Joined: September 2, 2000	Interesting, Roger - the 'tuning buttons' on my IIIa and 2.5 bass panels are riveted on (not screwed). Andy

from the factory, posted on May 8, 2021 at 05:52:34

Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010

This is what they do:

The early Tympanis were just glue no buttons.

Wow, it's amazing that those,.., posted on May 8, 2021 at 08:07:12
DustyC Audiophile Posts: 963 Joined: November 4, 2000	panels don't vibrate right out of the frames given the way those picture frame "u" staples fasten them down. But I guess it works! Did a double take on those fingernails.

RE: Buzz but not delamination?, posted on May 8, 2021 at 09:25:43
Norman M	"Did a double take on those fingernails." And are those fingernails glued on?

What is the red goop in the tube ???, posted on May 8, 2021 at 09:44:52
emailtim Audiophile Posts: 5373 Joined: July 2, 2017	What is the red goop in the tube ??? . 2022/03/30 Historical Records CENSORED

3M fastbond 30 NF, posted on May 8, 2021 at 09:47:08
emailtim Audiophile Posts: 5373 Joined: July 2, 2017	3M fastbond 30 NF . 2022/03/30 Historical Records CENSORED

RE: What is the red goop in the tube ???, posted on May 8, 2021 at 11:17:41
ketchup Audiophile Posts: 621 Location: Pennsylvania Joined: February 29, 2004	The red goop is most likely Loctite for the screws.

RE: What is the red goop in the tube ???, posted on May 8, 2021 at 22:30:40

pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008

couple different kinds of loctite. FOUR, to be exact.

The RED, I think is the 'hardening' type and will be a real Btch to remove.

the purple is a softer type and meant for smaller screw......I'd use THAT one....
Too much is never enough

https://www.henkel-adhesives.com/us/en/insights/all-insights

RE: What is the red goop in the tube ???, posted on May 9, 2021 at 01:46:01
Roger Gustavsson Audiophile Posts: 2054 Location: Huskvarna Joined: February 12, 2010	It looks like Loctite 268. https://www.henkel-adhesives.com/us/en/product/threadlockers/loctite_268.html

RE: What is the red goop in the tube ???, posted on May 9, 2021 at 10:16:47
Norman M	"... will be a real Btch to remove." The cure being worse than disease?

RE: What is the red goop in the tube ???, posted on May 9, 2021 at 10:44:23
pictureguy Audiophile Posts: 22597 Location: SoCal Joined: October 19, 2008	I'm not a Loctite removal expert, BUT the hardening stuff is tough.......And I think the Loctite literature calls out fasteners above a certain size. NOT 1/4" or whatever, for sure. The non-hardening is best for this applicaiton IF IT IS Necessary at all.... Too much is never enough

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