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View Full Version : Diaphragm problem in LE85 or 2405?



tjm001
12-16-2015, 01:39 PM
Just put the components into my just finished DIY L300s which are on the DIY forum. Initial testing revealed some distortion in the higher and louder passages of some music in one channel. From past experience I'm quite sure it's either a cracked diaphragm or the coil scrapping the side of the gap in one of the drivers. But before removing the LE85 and 2405s to have them bench tested by someone I was contemplating running some kind of sweep generator tones in the higher frequencies through the amp to try to reproduce the distortion and therefore isolate the culprit driver. I'm hoping it's the 2405s because I bought them on eBay about 5 years ago and never used or tested them until now. Whereas the LE85s I've had for many years and a JBL repair center just installed new aluminum diaphragms in them a couple of months ago. But have not had very good luck with JBL repair facilities in the last few years.

Anyway since I got rid of my Heath-kit signal generator about 40 years ago, I was wondering if anyone knows of some computer software program that would be useful in trying to do this. Maybe putting tones of 5 to 8Khz on a CD and playing it through the amp? Whatever. Any thoughts or ideas? Thanks.

Tom

grumpy
12-16-2015, 01:47 PM
easy one:

http://onlinetonegenerator.com/


...

Anyway since I got rid of my Heath-kit signal generator about 40 years ago, I was wondering if anyone knows of some computer software program that would be useful in trying to do this. Maybe putting tones of 5 to 8Khz on a CD and playing it through the amp? Whatever. Any thoughts or ideas? Thanks.

Tom

tjm001
12-16-2015, 02:20 PM
easy one:

http://onlinetonegenerator.com/

Thanks!

Wagner
12-16-2015, 03:53 PM
Just put the components into my just finished DIY L300s which are on the DIY forum. Initial testing revealed some distortion in the higher and louder passages of some music in one channel. From past experience I'm quite sure it's either a cracked diaphragm or the coil scrapping the side of the gap in one of the drivers. But before removing the LE85 and 2405s to have them bench tested by someone I was contemplating running some kind of sweep generator tones in the higher frequencies through the amp to try to reproduce the distortion and therefore isolate the culprit driver. I'm hoping it's the 2405s because I bought them on eBay about 5 years ago and never used or tested them until now. Whereas the LE85s I've had for many years and a JBL repair center just installed new aluminum diaphragms in them a couple of months ago. But have not had very good luck with JBL repair facilities in the last few years.

Anyway since I got rid of my Heath-kit signal generator about 40 years ago, I was wondering if anyone knows of some computer software program that would be useful in trying to do this. Maybe putting tones of 5 to 8Khz on a CD and playing it through the amp? Whatever. Any thoughts or ideas? Thanks.

Tom
Similar sounding experience here just lately with an irreplaceable Stephens spun aluminum diaphragm; the adhesive attcahing the voice coil to the aluminum was letting go and you could only hear there was a problem with certain material (notes/frequencies) on the "new" DVD release of "Magical Mystery Tour"
Took care of it with a capilary application of Bob Smith's "Insta-Cure":
http://www.bsi-inc.com/hobby/insta_cure.html
Remove the diaphragm, look for and hopefully see the beginnings of separation and then apply some of this stuff on an angle so that capillary action carries it all the way around the joint but no where else
I had to apply a little light pulling action to actually see that my joint was starting to fail and was the source of the harsh raspy popping on those certain frequencies
Find a piece of music that excites the problem predictably and isolate it by disconnecting drivers until you find it through elimination if you have no other way; that's what I had to do
At least mine was easily identifiable as to coming from only one cabinet
Try to catch it before it totally separates and then you'll have a big mess trying to realign it properly
Catch it in time and it will be good as new! (probably better with this stuff)
A little goes a LOOOOOOOOOOOOOOOOOOONG way
Hope that's it! :yes: (bet you it is, that glue is pretty old now)

Good luck!
Thomas

macaroonie
12-16-2015, 04:53 PM
NCH tone generator will let you run a sweep. You can also run it up incrementally. Free online

tjm001
12-16-2015, 05:40 PM
NCH tone generator will let you run a sweep. You can also run it up incrementally. Free online

Thanks man. I'll check that one out too.

FYI.. The speakers sound great! Actually brought tears to my eyes after all those 10 years in boxes in the closet. It's just that little rattle-like sound in one of them at certain high frequencies. I just hope it's not the LE85. I've had nothing but problems since the JBL authorized repair center in Chicago put in the wrong diaphragms in them about 10 years ago. I then find original type aluminum diaphragms and take them to another JBL repair center across the river in Maryland to be installed and now maybe more trouble. I just hope it's the 2405s. Diaphragms are only about $33 and easy to install.

Tom

Doc Mark
12-17-2015, 08:41 AM
Morning, Tom,

Have you removed the offending diaphragm, and cleaned the gap really well? Sometimes just a tad of flotsam and jetsam gets into the gap, and that can cause a buzzing sound at certain frequencies. Cleaning the gap is fairly easy, but you do need to be careful removing, and reinstalling the diaphragm. Just a thought, but it costs you nothing to check the gap, and may solve your problems. Good luck, and God Bless!

Every Good Wish,
Doc

P.S. check post #10 in this link, and read about someone else who had the same problem as you, and resolved it by cleaning the gap and removing tiny metal particles.
http://www.audioheritage.org/vbulletin/showthread.php?29919-Diaphragm-distortion-on-le85

Mannermusic
12-17-2015, 11:15 AM
Thanks man. I'll check that one out too.

FYI.. The speakers sound great! Actually brought tears to my eyes after all those 10 years in boxes in the closet. It's just that little rattle-like sound in one of them at certain high frequencies. I just hope it's not the LE85. I've had nothing but problems since the JBL authorized repair center in Chicago put in the wrong diaphragms in them about 10 years ago. I then find original type aluminum diaphragms and take them to another JBL repair center across the river in Maryland to be installed and now maybe more trouble. I just hope it's the 2405s. Diaphragms are only about $33 and easy to install.

Tom

Glad to see the project is coming together! Voice of experience: Beware the aftermarket $33 diaphragms. Don't cut it in my experience in terms of output or response. Can check the data base here as well. Hopefully Doc is right - junk in the gap. Mike

tjm001
12-17-2015, 03:12 PM
Glad to see the project is coming together! Voice of experience: Beware the aftermarket $33 diaphragms. Don't cut it in my experience in terms of output or response. Can check the data base here as well. Hopefully Doc is right - junk in the gap. Mike

Thanks. After testing for a few days I'm of the opinion that there is a very high probability that Doc is right. And that it is the LE85. The thing I remember after picking up the LE85s from the JBL repair facility was the comments of the tech. He said there sure was a lot of debris in the gaps and that the last person that worked on them (Chicago JBL facility) did not know what they were doing.

So I'll pull it out and see what I can do. If that fails I take it back to JBL Maryland.

They still sound pretty good and sure look real L300s! Thanks all for the tips so far.

Tom

Wagner
12-17-2015, 04:46 PM
Thanks man. I'll check that one out too.

FYI.. The speakers sound great! Actually brought tears to my eyes after all those 10 years in boxes in the closet. It's just that little rattle-like sound in one of them at certain high frequencies. I just hope it's not the LE85. I've had nothing but problems since the JBL authorized repair center in Chicago put in the wrong diaphragms in them about 10 years ago. I then find original type aluminum diaphragms and take them to another JBL repair center across the river in Maryland to be installed and now maybe more trouble. I just hope it's the 2405s. Diaphragms are only about $33 and easy to install.

Tom
I'm telling you after reading your additional posts and others, clean the gap thoroughly as Doc suggests (easy) and check that VC to diaphragm joint carefully
Especially after reading you write "rattle-like" 'cause that's exactly an accurate descriptive of how mine sounded when they started to come undone (unglued)
And he's probably right, that "tad of flotsam and jetsam" is most likely a tiny crumb of ancient adhesive that's flaked off (where do folks think that the trash in all those gaps comes from in the first place? Rotted foam and out gassed adhesives!)
IF it still measures well (DCR wise) and it still passes a signal reasonably well when it's not "rattling" then that's about all it can be, a mechanical failure combined with a possible impediment caused by unwanted debris and that my friend is a simple matter of adhesive that's outlived it efficacy

Clean it all up and run a bead of that Insta-Cure around it anyway while you've got it apart
It's superior to anything they had when they made that one, that's for sure
You'll never suffer an adhesive failure with that Bob Smith stuff, I can promise you that
Then you'll be good for another 30 years or so or until you just wear it out, whichever comes first
(it's easy to source as well, all the Hobby Towns carry it for one source and theirs is always fresh and date coded))

It's definitely worth a go before you ship it off to someone else; especially if you could repair it as good as new yourself for less than $5 bucks and an hours time
Definitely a lot quicker, cheaper and just as good as before, short of a new part with zero risk (can't make it any worse than it already is!) :)