Intro and request for repair help

[chilledspode]

Hi!

I am brand new here, and I have a immaculate set of L65's, even the black fuzz under the original smoked glass lives on. This looks to be a great resource, I expect to spend some time in here.... :-).

I live in the Canadian Arctic and so I have some interesting logistical issues when I need equipment repairs done.

I have a question: one of the speakers has started to develop a slight crackling when playing, left channel only and only when playing vs sitting idle but powered up. I do not possess the knowledge to determine if it is a midrange driver or a crossover failure starting. This issue or one like it seemed to crop every couple of years and seemed to be related to the presence and brilliance controls getting dirty and if you spun them repeatedly the issue would go away - that trick isn't cutting it anymore.

Can someone guess what I am up against - as I will have to dismantle and send the offending assembly out for repairs.

Kind regards,

Mark

[johnaec]

First, you need to determine if it's just a single speaker in the cabinet or something that's coming through all the speakers in that cabinet. If the noise comes through all the drivers, you have either connection, crossover, or amp/preamp problems. If so, switch the L65's to opposite channels, L-R, to see if the sound goes with the speaker or the channel.

If the noise is obviously coming from just one driver in the cabinet, swap it out and replace it with the driver from the other cabinet. If the sound goes away, the problem is with the driver. If you still have the sound in the replacement driver, the crossover is the most likely culprit.

John

[chilledspode]

Hi John,

Sound (no pun intended) advice.

I will do as you suggest - should have been able to come up with that myself.... sigh

On a general note what is the general failure modes of old but not abused speakers, beyond deterioration of the paper/foam driver elements.

Should speakers of this vintage have the crossovers rebuilt as a matter of course?

Mark

[johnaec]

A common point of failure on older speakers is corroded connections. As far as crossovers go - someone else will have to answer that, though I'm sure the stock ones can be improved upon. I just don't know if originals deteriorate or not. I've got a pair of L65A's and 4315A's and the original crossovers still seem fine to me, (as far as they go...) Bypassing the caps seems to be highly recommended. Search on "bypass caps" for lots more info.

John

[chilledspode]

Thanks John,

Let me poke around on the caps issue - I have always hated those things....

Cheers

Mark

[johnaec]

Another thing to check is that all the internal connections to the speakers are solid. You just have to take things one step at a time - 'process of elimination.

John

[Zilch]

Welcome, Mark.

If exercising the presence and brilliance controls used to fix it, I'd start with replacing those L-Pads with new ones, available from Parts Express or a similar source up there, if you have one....

[chilledspode]

if you have one....

Good to see a well rounded sense of humor.... :-) The nearest decent audio shop is probably 1,000miles away

I poked around the PartsExpress site and L65 returned '0' results. Great site, and thanks for pointing it out, but I didn't see where I could replaement JBL parts for my speakers - am I missing something?



Mark

[Zilch]

am I missing something?Yes. The standard L-Pads they sell there. The quality of the 100W ones is better than the 50W, but they are larger in diameter and may not fit. Also, you have to choose 3/8" or 1" shaft length for mounting compatibility.

Somebody (Johnaec?) who has accessed or replaced L-65 L-Pads will have to advise you on which to buy. At $30 for four of them, they may just solve your problem....

See also:

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L65%20Jubal%20ts.pdf

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L65A%20Jubal%20ts.pdf

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L65B%20ts.pdf

[chilledspode]

Wheee!

What a read - just poked around on a 'L65' search. I am a pretty good engineer of the civil variety and I can hold my own in most discussions but I feel like a 5yr old in here.

Thanks to all, what a site!

Mark

the more I learn the less I know