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Repairing JBL E140...or not...

#22
Badass MOFO said:
E-140s are killer drivers. I own several of them. I don't believe that any GK amp is capable of destroying them unless you are doing something wrong. On the other hand I could easily blow up any GK driver with a number of different amplifiers.
Does your amp have an impedance matching switch? If so, make sure that you do not overload the output.
A heads up in case you were not aware ..JBL drivers are reverse polarity, in other words, you have to apply a positive bias (instantaneous DC voltage) to the NEGATIVE terminal on the driver to generate forward (or outward cone excursion) of the driver and visa-versa. It is very important to make sure that all of the drivers are in phase when using multiple drivers otherwise you will destroy the one that is wired wrong ..this goes for all multiple driver scenarios.
I do not recommend moving JBL driver cones with your hands as there is only a couple of 1/thousands of an inch tolerance in the field gap for the voice coil windings and they will interfere so it will scrape.
Hope this helps!
Click to expand...

Here's a tech paper on the polarity issue: [Invalid or Expired Link Removed]
 
#23
Good info from all. Thanks - had polarity right. Bass mofo - you are correct - the outside back aluminum nameplate has a mesh glued on the underside to prevent screws and ping pong balls from going down the throat of the speaker and on the inside of the centre (seen after removing dust cap, there was a finer foam filter glued on at one time. What I am guessing is that this foam deteriorated and bits fell off, gummed up a bit and slipped into the space between magnet and voice coil. The cone doesn't rub like you would expect from say a shifted magnet but somethings there. I can gently and evenly move cone slightly forward and see goop stuck to coil (which is a plain silver surface - not the actual wires) so with patience , perhaps a bit of solvent, a very thin shim stock to clean space between - I might luck out - as Bill Whitehorse said - nothing to lose - next step is recone anyway. Waiting for the snow to melt anyway - might as well stay busy.
 
#24
So you have an anodized aluminum bobbin, they also suffer from blistering when they get hot (which is why they are no longer used, and just about all you see are aftermarkets)

If the foam deteriorates, try a thin business card strip soaked in lacquer thinner run around the ID of the bobbin as many times as necessary, changing strip with each pass.
 
#25
Ha! Thanks aged horse - lacquer thinner dissolved the goo off the bobbin and some business card thickness manila stock just fit in the air gap. Did a test run with speaker out of cab and no dust cap and its free and smooth. Next step - dust cap and glue - will try Weber as suggested. Did some poking around and discovered the aluminum vs paper cap discussions - think I'll stick original. Any suggestions if, and what one should glue back over the vent hole on the inside before closing up?
 
#27
Badass MOFO said:
The wattage rating is 400 watts continuous program and 200 watts continuous sine wave for the 2225's and the E 140's the K 140's are rated at 300 watts continuous program but those are only ratings that they need to give so you have some idea of what you are dealing with. They can take many times the rated power. I have done it too. I used to have a K 151-8 rated for 300 watts and it handled 800 watts continuous R.M.S. 20-20,00o kHz (and that is way underrated) driven to clipping and the driver's motor didn't even get warm.
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+1. I use a Sunn 200S with a pair of K-140-16s powered by one side of a QSC CX1202v. With the 8 ohm load, that's about 800 watts RMS at full bandwidth and .05%THD. I've cranked it to the point of almost clipping and the speakers take it fine and ask for more. Great speakers, although I wish there was a smidgeon more high end. I found a custom cab with a K-140 and K-110, but I want to lower the output of the K-110 and maybe raise the crossover point a bit. It's also heavy as sin. But it sounds great.

I love JBLs.
 
#28
edwinhurwitz said:
+1. I use a Sunn 200S with a pair of K-140-16s powered by one side of a QSC CX1202v. With the 8 ohm load, that's about 800 watts RMS at full bandwidth and .05%THD. I've cranked it to the point of almost clipping and the speakers take it fine and ask for more. Great speakers, although I wish there was a smidgeon more high end. I found a custom cab with a K-140 and K-110, but I want to lower the output of the K-110 and maybe raise the crossover point a bit. It's also heavy as sin. But it sounds great.

I love JBLs.
Click to expand...

You are well into the danger zone with the E-140's, especially without a HPF. You THINK they take it fine and you THINK they are asking for more but I know that you are beyond the mechanical limits of the spider on that speaker. Won't take long before you find your speakers with a loose, sprung suspension. Yes, it does happen and pretty often. It's by far the most common failure mode for the D/K/E series speakers.
 
#29
agedhorse said:
You are well into the danger zone with the E-140's, especially without a HPF. You THINK they take it fine and you THINK they are asking for more but I know that you are beyond the mechanical limits of the spider on that speaker. Won't take long before you find your speakers with a loose, sprung suspension. Yes, it does happen and pretty often. It's by far the most common failure mode for the D/K/E series speakers.
Click to expand...

True, but it's worth it. I want to get them reconed at 8 ohms anyway. Neither has the original cone, so I'm not ruining a vintage driver in perfect condition. In the meantime, I get the sound I want, which is what it's all about.

Back in the 70s I blew the K drivers up regularly, but I played even louder then.
 

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