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dahopp
01-29-2009, 10:30 AM
Hello Everyone,
I just found this forum, and see there's a wealth of knowledge here. Hopefully someone can give me some direction, as I don't know much of anything about working on speakers.

My dad bought a pair of L75's, a pair of L26's, and a pair of 4311's new while he was in the army stationed in Germany in 1973 or 74. He shipped them all home, and the speakers stayed in the basement unused through my childhood. The L26's were sold for a few bucks after the surrounds fell apart. But now I've been enjoying the 4311's for the last 6 years, and after refoaming the L75's I've been using them as well.

The Problem: One of my LE8T's comes and goes intermittently. If it isn't working, turning up the volume louder (but not really loud) will usually kick it in. The problem is recreatable connected to a different receiver. I pulled the driver from the cabinet and hooked it directly to the receiver, and it looks like the connection/solder from the terminals to where the wires punch through the cone are fine. Last night I set the volume low, and listened to it cut in and out while playing a song. I'm a computer tech, but I know nothing about how to procede further in troubleshooting this, and fear I'm probably not cablable of fixing it. I'm also not sure how much it would be worth spending to fix this.
Thanks for your insight :)

Mr. Widget
01-30-2009, 10:04 AM
Unfortunately since the L75 is a "full range" system... there are no crossover or other parts to fail other than mechanical connections internally. Does the driver cut in and out outside the cabinet when wired directly? How sound do the spring terminals on the driver itself seem?

Do you think your dad still has the receipt? If he does, your speakers are under warranty. Also, these drivers are old enough to have the now yellow Lans-a-loy surrounds... they need to be replaced. Your LE8Ts and passives all need new surrounds or the DOT-3 treatment (do a search) for you to get the proper bass response from these little guys.


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dahopp
01-30-2009, 03:06 PM
The driver does cut in and out when wired directly to the receiver, and the spring terminals seem to be biting well on the wire, so I'm confident that's not the problem.
I did already replace the Lansaloy surrounds with new foam a year or two back. It was my first attempt, and it came out pretty well. Certainly not impeccable, but not terrible either.
I get the feeling that the driver needs to be completely disassembled to get an accurate diagnosis. I'm not sure what all would be replaced and what work is performed if I had it reconed. Would having the speaker reconed allow for the problem to be fixed if it were just an connection issue (as it seems), rather than failure of the voice coil, etc...?
Can anyone give me a ballpark figure on having my LE8T reconed?

BTW are you serious about a lifetime warranty for the original owner?

Mr. Widget
01-30-2009, 08:51 PM
BTW are you serious about a lifetime warranty for the original owner?Absolutely, however a re-surround would void that.:( JBL only recommends a recone.

Send a PM to Edgewound or Oldmics both are factory authorized and pretty clever with "strange problems."


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TonyM
01-30-2009, 09:56 PM
Carefully connect an ohm meter to the tinsel leads between the frame and cone. Tap on the cone or carefully push it in and out. If the reading doesn't change but it does change when you measure accross the terminals the problem might be where the leads connect to the bottom of the posts. If it does change when you measure accross the leads then they probably need a recone.

I had an Altec 416B do the exact same thing. I replaced the posts and they're still cooking along.

My first JBLs were a used pair of Lancer 44s with the LE8T drivers that I purchased at Recycled Stereo in Berkeley. While the store is long gone we still have the speakers and they still work.

Mr. Widget
01-31-2009, 09:33 AM
I purchased at Recycled Stereo in Berkeley. While the store is long gone we still have the speakers and they still work.Loved that store!!!

I was going to suggest carefully alligator clipping the amp leads directly to the tinsel leads as an alternative test for this... I like your method better.


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TonyM
01-31-2009, 10:54 AM
Yep, I miss all of that stuff. As I remember it was part of the Pacific Stereo chain and they sold all of the trade in stuff there plus B stock items and whatever. As a student it was the only way I could get some of the better pieces plus it was just fun to wander around there. Every week the shelves would be stocked with different trade ins.

If you're tapping on the cone the meter might jump a little because you are inducing a little voltage in the voice coil but it shouldn't go fully open.

If you get to the point that you suspect the post you can connect the ohm meter from the wire under the post to the top and wiggle stuff around and see if the meter moves around, it shouldn't.

dahopp
02-08-2009, 06:51 PM
I checked resistance at both the posts and on the tinsel leads, and both read between 1.2 and 1.4 ohms as I gently moved the driver in and out. I then did hold the speaker wire from the receiver directly to the tinsel leads, and was able to confirm that the problem was still there when bypassing the posts.
I believe it's beyond my means right now to have this driver reconed, and it almost seems I would want to do both that I have rather than one. Any other options for me? I'm assuming not....
Anyone want to buy a pair of L75's? Surrounds replaced, one is working well. Cabinets are pretty clean, and I have the original boxes to ship them in.