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JBL K140's [message #23515]

Tue, 28 July 2015 22:23

oren hudson
Messages: 274
Registered: March 2008
Location: Gastonia, NC

Senior Member

I've got a '69-ish 2x15 cab that has JBL K140's in it. The bottom speaker developed a rattling type noise. I discovered that if I pushed in on the vent grill on the magnet, it pretty much quieted it and let that beautiful sound be perfect. I then put a piece of gorilla tape across the opening and the rattling noise went completely away resulting in a perfect sound. Knowing that the vent needs to be open, any ideas as to what the issue could be?

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Re: JBL K140's [message #23516 is a reply to message #23515]

Tue, 28 July 2015 22:30

pleat
Messages: 1454
Registered: June 2004
Location: Belding, Mi

Senior Member

I had a D120F that on certain notes I'd hear a rattle. Turned out that the dust cap was the cause. I used a clear bead of GE silicone glue around the dust cap and problem solved.
pleat

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Re: JBL K140's [message #23517 is a reply to message #23516]

Tue, 28 July 2015 22:44

oren hudson
Messages: 274
Registered: March 2008
Location: Gastonia, NC

Senior Member

I have a feeling that you're onto something there pleat. Like yours, it's not every note, and I'm assuming that blocking the vent reduced the flow of air and didn't shake the dust cover as much, quieting it down. Thanks.

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Re: JBL K140's [message #23518 is a reply to message #23515]

Wed, 29 July 2015 06:36

stevem
Messages: 4775
Registered: June 2004
Location: NY

Senior Member

x2, but do not use too much silicone or you will dampen the high's, in fact thick gel type super glue is what you would get in a complete re-coning kit to apply there ,and that would be my first choice and is what I use.

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Re: JBL K140's [message #23531 is a reply to message #23515]

Thu, 30 July 2015 11:36

Kustom_Bart
Messages: 601
Registered: October 2010
Location: Greenville, MichiGUN

Senior Member

Pleat is right on the money, I have dealt with this myself, do not use super glue, get the recone glue that is used for this purpose, it is cheap and will work perfect. The couple that I did, once you lifter a little to try to get under the cap, the entire cap came off. make sure if it does, do NOT allow anything to get into the voice coil, like old glue. It will destroy the coil and the speaker will need to be reconed after that, here is how to reinstall the cap. While you have it off....polish that puppy up with some brasso or simi-chrome, just be gentle with it. apply a bead of glue where it used to set just below and just above (basically and double bead touching each other) and set it in place and then take a shot glass and turn it up side down and set it on top of the cap to hold it down in place and it will not come off in your lifetime. Smile

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Re: JBL K140's [message #23540 is a reply to message #23531]

Thu, 30 July 2015 23:23

pleat
Messages: 1454
Registered: June 2004
Location: Belding, Mi

Senior Member

Maybe with an Altec aluminum dust cap, but the JBL D140 aluminum dust cap, its only .005 of an inch thick. A little bit thicker than aluminum foil. They crinkle real easy.

As I said in my original post, I used GE silicon glue. It may have dampened the high's a bit, but after 52 years of loud rock and roll, My old ears couldn't hear any difference other than the rattle was gone.
pleat

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Re: JBL K140's [message #23544 is a reply to message #23540]

Fri, 31 July 2015 08:51

C4ster
Messages: 686
Registered: June 2001
Location: Mukwonago, WI (Milwaukee...

Senior Member

I have found that black RTV works very well. Just clip the tip to about 1/8" and lay the RTV in the channel around the dust cover. The RTV stays flexible and sticks to anything. Besides, it's black and blends in.
Conrad

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