JBL K120 longevity

JBL K120 longevity

Postby bpg21 » Mon Apr 25, 2011 9:39 am

Hi All,
I came across a pair of original JBL K120s that have never been reconed. Just wondering how much longer a 35 year old speaker is destined to last. Are they more suseptible to damage a louder volumns? Is the tone going to be better than a recone?
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Re: JBL K120 longevity

Postby mijknahs » Mon Apr 25, 2011 7:44 pm

If its in good shape it can still last a long time. Recones sound good too.
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Re: JBL K120 longevity

Postby Pete B. » Thu Apr 28, 2011 8:14 am

mijknahs wrote:If its in good shape it can still last a long time. Recones sound good too.

I hope you're right.
I just spoke to the guy about this one that popped up on our local Craigslist.
Turns out I know the guy, and will meet to check it out and buy it tomorrow.
TigerStrat tells me this guy is a great guitar player (Ben S.), so I think we will jam a little too.
Here it is:
http://portland.craigslist.org/mlt/msg/2349366818.html
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Re: JBL K120 longevity

Postby mijknahs » Thu Apr 28, 2011 8:33 am

I've used some of my JBLs for over 12 years and never had a problem with them. Never blown a speaker yet.
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Re: JBL K120 longevity

Postby ChiroVette » Mon May 23, 2011 10:42 pm

I have a related question:

I have a Fender Twin with a couple of JBL K120's in them. Like all K120's they are about 35 years old, give or take. Anyway, when playing my "Jerry sound" through them, I am getting what sounds like a microphonic tube sound at the high end, particularly when I play leads on the high E, B, and G strings. It gets less pronounced when I dial down the treble a little. Anyway, my amp guy is doing a load of work on my Twin trying to track down the problem, but after checking all the tubes and determining none of them were microphonic, he thinks that the speakers might need to be re-coned. He is still not 100% certain yet, and has some caps to change and other issues to address with my old twin, but we are not incredibly optimistic about it, which means I may have to re-cone one or both of them.

Now my questions are as follows, and both assume that the speakers need to be re-coned, even though I am not 100 sure yet:

1. What are the differences between the K120 and the E120? I always thought Garcia used the K120's, but just recently found out that he used the E120's. I also always assumed that K being a later letter in the alphabet, would designate the K series as better than the E series, but I was told this was not true.

2. I heard that some JBL's can be re-coned with the other cones/voice coils. So if this is true AND the E120 is a better speaker than the K120, can I have my K120's re-coned with E120 cones and voice coils? I called Simply Speakers yesterday and I didn't ask them this, but I did get a price. The guy told me that it costs $230.00 each speaker plus about $18.00 UPS ground shipping for both, which comes out to about $500.00 for the re-cone.

3. He also said that when you re-cone you should absolutely change the voice coil, and that the price he gave me includes both the re-coning and the voice coil. Is this a decent price? Do you guys know of and/or trust Simply Speakers?


Thanks guys! :)
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Re: JBL K120 longevity

Postby mijknahs » Mon May 23, 2011 10:59 pm

The K120s have an Alnico magnet. The E120 has a ceramic magnet. The K120's were made in the 70's. The E120 in the 80's and 90's. The D120 is what they used in the 60's and early 70's.

The only recone kits for the K120 are the same kit as for the E120. I think this gives them a little bit higher power rating than stock. The price you were quoted is good especially if using genuine JBL parts (normally about $300/each). I recommend going with the JBL parts as opposed to aftermarket if you can afford it. It will be like having a brand new speaker.

Hopefully the speakers don't need to be reconed. Can you check them with another amp? I had a weird sound with my amp a few months ago that only made the sound on certain notes when past a certain volume. It turned out it was a problem with the soldering inside the amp. I re-soldered a bunch of crucial spots and it went away.
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Re: JBL K120 longevity

Postby mkaufman » Tue May 24, 2011 7:29 am

Good point - certain frequencies at certain volumes can cause components to vibrate. Could be a cold soldier joint in the amp. I had that happen once.

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Re: JBL K120 longevity

Postby mijknahs » Tue May 24, 2011 8:17 am

I would never have suspected that a cold solder joint was the problem. I mean the amp was working! Only at certain resonant frequencies would this bad sound occur. If not for Brad and Waldo's advice I would have suspected the speakers were going bad.
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Re: JBL K120 longevity

Postby vwjodyme » Tue May 24, 2011 8:49 am

Yeah, samething just happened to me. got wierd sounds only when playing certain notes/chords. really freaked me out...thought it was the new guitar at first, but turned out to be the connection in the cab :lol:
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Re: JBL K120 longevity

Postby Vin-Tone » Fri Nov 09, 2012 6:49 am

JBL Tech Bulletins use to state the average life span for Musical Instrument or Professional Products was estimated at 10-15 years in modest use applications.
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Re: JBL K120 longevity

Postby TI4-1009 » Fri Nov 09, 2012 7:34 am

Vin-Tone wrote:JBL Tech Bulletins use to state the average life span for Musical Instrument or Professional Products was estimated at 10-15 years in modest use applications.


That would translate to about 300 years for me... :lol:
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Re: JBL K120 longevity

Postby mgbills » Fri Nov 09, 2012 9:24 am

+1 on trying them in another cab.

Or easier yet, hook them up to another amp & leave them in the cab. Run them through a wide band of tone stack settings.

I sure wouldn't want to swap original cone K's for recones if it wasn't necessary.

Most of mine are original. I play them almost every day, and am feeling like they're doing fine.

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Re: JBL K120 longevity

Postby JonnyBoy » Sat Nov 10, 2012 2:35 pm

I got an aftermarket e cone from sound speaker repair and they were almost identical clones to an actual kit I had. That's a cheaper route and that speaker sounds awesome. I do totally understand wanting OEM kits and the E kits are the Kits for the k's they were designed to work for both when the E's came out. Really they are the same speaker, but one is alnico one is ceramic.
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Re: JBL K120 longevity

Postby Vin-Tone » Wed Nov 14, 2012 5:57 am

There are other differences between the K and the E besides the magnet. Again the E kit will work, but it will not sound like original K.

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