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View Full Version : Diaphragm distortion on le85



andychris
12-01-2010, 04:10 AM
Hello

I've got a pair of LE85. They've got their original diaphragms, but I've got some distortion at high level when I listen to soprano singers. I would like to know if those diaphragms need to be change even if their coils are not cut ? Do they change their sound when they become to be old ? They are in absolute fine optical shape.

thanx for you answers

Tim Rinkerman
12-01-2010, 04:42 AM
How do you know it's the driver and not the crossover?

timc
12-01-2010, 05:29 AM
Or the amplifier clipping?

andychris
12-01-2010, 08:00 AM
Both speakers do the same distortion. neither the treeble neither the wooffer drivers have that distortion, and I've got 3 amplifiers,,,,same probleme............

timc
12-01-2010, 08:49 AM
Since it only occurs on high SPL, the first thing i would check is the leads going from the terminals to the voicecoil. They might be buzzing against the spider or cone.

Second, I would couple the drivers directly to the amplifier and do a frequency sweep. For this you could just disconnect the woofer and treble.

yggdrasil
12-01-2010, 09:03 AM
For each dia; Slightly loosen the screws holding the dia. Push the dia to the extreme in one direction. Test for noise. If still not ok, then redo the process in a slightly different direction.

Report back if you can't find a position without noise.

Mr. Widget
12-01-2010, 09:24 AM
I've got a pair of LE85. They've got their original diaphragms, but I've got some distortion at high level when I listen to soprano singers. I would like to know if those diaphragms need to be change even if their coils are not cut ? Do they change their sound when they become to be old ? They are in absolute fine optical shape.Yes they may change their sound as they get old. Well, not old but rather played a lot or played loudly a lot. I'd suspect you do in fact need to replace the diaphragms. Go a head and check all of your other options first as the proper JBL replacement diaphragms are fairly expensive, though luckily they are still available... this may not always be the case.

Actually the JBL replacement diaphragms are the aluminum diamond pattern edged diaphragms that were developed in the latter part of the 70s/early 80s... they are slightly smoother and more extended than the original LE85 diaphragms that were developed back in the 40s/50s.

Widget

jcrobso
12-01-2010, 09:56 AM
Since it only occurs on high SPL, the first thing i would check is the leads going from the terminals to the voicecoil. They might be buzzing against the spider or cone.

Second, I would couple the drivers directly to the amplifier and do a frequency sweep. For this you could just disconnect the woofer and treble.
Disconnect the other speakers would be the best option so only the Le85 hooked up.

Paul D
12-01-2010, 10:03 AM
I had something similar to this happen when I accidentally crossed them over very low.
At high levels I could actually hear the diaphragms moving, trying to produce the lower frequencies. My active crossover had a button for dividing the freq. by 10 for subwoofer use so they were going down to 100 instead of 1000 hz. The suprising thing was that it wasn't noticable at low volume at first.:banghead:

andychris
12-06-2010, 08:21 AM
Hello

So I found the probleme. In fact some little piéces of metal where inside the air gap where the coil is placed of course. Now it works fine and I can easily adjust the dias as I couldn't do it before.

but I've got a question, I've got aluminium dias and I would like to try titanium ones, but what are the real references of those dias, they mesure 6 ohm. A friend of mine gave me a pair of D16R2425 and they work fine on my LE85 but are aluminium. I know that JBL says that the replacement dias are 2421 but I can't see any differences with 2425, in fact I can read the references 21956 on each dias LE85 or 2425,,,,,,,so, who knows the truth ??????

Mr. Widget
12-06-2010, 09:11 AM
So I found the probleme. In fact some little piéces of metal where inside the air gap where the coil is placed of course. Now it works fine and I can easily adjust the dias as I couldn't do it before.Great!



but I've got a question, I've got aluminium dias and I would like to try titanium ones...Why? Titanium is only used due to it's inherent superiority in durability. For any high frequency device rigidity and lightness of the material are keys to superior sonics... beryllium is the best followed by magnesium and then aluminum... titanium is even less stiff but it is more resilient and therefore less likely to fail when abused or pushed hard in professional applications.


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andychris
12-06-2010, 09:23 AM
OK but why do most of poeple say that titanium dias have smoother sound and better sound quality ? Everybody do not agree whith that ?

Mr. Widget
12-06-2010, 10:02 AM
OK but why do most of poeple say that titanium dias have smoother sound and better sound quality ? Everybody do not agree whith that ?Most people say that? According to my personal experience and the engineering staff at JBL, the opposite is true. If you look at the high end JBLs currently made for home use, as opposed to stadium use, you will find they are using Aluminum, Magnesium, and Beryllium as their models get progressively more expensive.

As for what people say... don't trust anything you read on the internet without some additional corroboration... including anything I say... though I am almost always right. :D


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timc
12-06-2010, 11:29 PM
Great!

For any high frequency device rigidity and lightness of the material are keys to superior sonics...


Widget

Really? I thought Titanium had a better stiffnes to weight ratio? Or maybe im confusing it with Strength to weight ratio?

-Tim

Mr. Widget
12-07-2010, 12:16 AM
Really? I thought Titanium had a better stiffnes to weight ratio? Or maybe im confusing it with Strength to weight ratio?Ti has a greater strength to weight ratio than Al but it is far more resilient like high quality steel... great for bike frames, not so much for HF diaphragms. ;)


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Rolf
12-07-2010, 12:15 PM
I agree. The Aluminum sounds better.


Most people say that? According to my personal experience and the engineering staff at JBL, the opposite is true. If you look at the high end JBLs currently made for home use, as opposed to stadium use, you will find they are using Aluminum, Magnesium, and Beryllium as their models get progressively more expensive.

As for what people say... don't trust anything you read on the internet without some additional corroboration... including anything I say... though I am almost always right. :D


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4313B
12-07-2010, 12:23 PM
One of our operatives in Northridge added some additional information a few years back...

Compression Driver Diaphragm Longevity (http://www.audioheritage.org/vbulletin/showthread.php?3233-Compression-Driver-Diaphragm-Longevity)