JBL L65A restoration

[nasinn]

Hi markd51, thanks for that will study it in detail. Kits have arrived at the post office so I'll pick them up after my holiday and report back on the progress.

On the topic of the crossovers I just got a oscilloscope / signal generator and had a bit of a play with one of the speakers. What I did was feed through my amp a sine wave of different frequencies and recorded the peak to peak voltages of the input terminals and of each of the driver terminals. The scope does not have one of these automatic response plot generator so it was a bit of a manual changing of frequencies and noting the Vpp values. With this Vpp information of the input vs. the drivers I did the voltage gain https://en.wikipedia.org/wiki/Gain_(electronics) plot, see below. One not is I don't think I was quite at the center of the brilliance / presence pads, but I can redo this all if there is any value in this sort of analysis.



In addition to those measurements I also set up the crossover schematics in KiCad and ran a spice simulation of the frequency response and added to the plot results I was a bit unsure on the L4 connection as the original schematic has some strange inductor symbol (I am not an electrical engineer - so I am keen to hear what that means but my googling tells me its a tapped inductor but it was not clear to me where to connect the R7 to, but the sim did not ran when I connected it at the bottom of L4).



Not sure what the value of all this is, or if I was just keen on trying out the oscilloscope haha... My hope would be that this could give some indication of the state of the caps, but I am very keen to get some input on this stuff from someone with experience in this sort of stuff.

Cheers,
Jonas

 

[nasinn]

In other news I picked up a pair of L20Ts from a friend, they were pretty banged up and one tweeter was dead. With the help of the forums here I repaired the broken wire in the tweeter and it is back in operation Other than that the foam was OK, not great but will let it be for now. The cabins are quite damaged so I will give them some love and maybe write up a post on that somewhere here, then the idea is to make a speaker selection switch as my amp does not have one (should be okay to have it as a parallel connection with A / B / A + B as both sets are 8 ohm and amp should handle 4 ohm), so I'll be able to enjoy some tunes in the kitchen - so lots of projects in the pipes.

Cheers

 

[SaturationPt]

L20t should have rubber surrounds on the woofers. Are you talking about the foam damper in the 035Ti?

 

[nasinn]

L20t should have rubber surrounds on the woofers. Are you talking about the foam damper in the 035Ti?

Yes the foam referring to the one in the tweeter, poking it it came back, not instantly so maybe i replace it at some point but first I'll do the boxes up.

 

[nasinn]

Long time no update,

Took my a while to find the time to do both speaker cone refoams, each took about a day to complete with all the setting. In general it was quite straight forward with the simply speakers kits, although two things confused me a bit:

• There was no mention or instructions of how to install the mass ring, which these seem to have but I somhow managed
• The adhesive set contained a treatment for the surrounds but I don't think they should be applied to these types of surrounds so I did not

Attached are a few images to give a feeling for it, but all in all I can't hear any difference but the look is just so much cleaner now, so my mind is at rest

Jonas

 

[Hannes123]

Grüezi! Das sieht gut aus, saubere Arbeit

 

[Hannes123]

...another L65A owner here. Are you planning to do any upgrades to the crossover?

 

[markd51]

Long time no update,

Took my a while to find the time to do both speaker cone refoams, each took about a day to complete with all the setting. In general it was quite straight forward with the simply speakers kits, although two things confused me a bit:

• There was no mention or instructions of how to install the mass ring, which these seem to have but I somhow managed
• The adhesive set contained a treatment for the surrounds but I don't think they should be applied to these types of surrounds so I did not

Attached are a few images to give a feeling for it, but all in all I can't hear any difference but the look is just so much cleaner now, so my mind is at rest

Jonas

The Woofers and all else look super! Bravo!

 

[Mr Boochie]

Welcom to the forum!

Yeah, they did a really "lovely" job to the Woofers! There might be the small chance of replacement foams, but I might guess too much damage was previously done, and would likely suggest as you surmised, complete new aftermarket Recone Kits from such like Simply Speakers.

I;d likely go this route myself. Might be wiser to replace all, Voice Coils-everything...

https://www.simplyspeakers.com/jbl-recone-kit-aftermarket-jbl-122a-RK-JBL122a.html

Yeah. My L166 find had the woofers messed up like that. I went with cone and voice coil. The Aquaplas was applied onto the front, as the cones aren't made anymore with the Aquaplas on the back from JBL. Sound seems okay.
Speaker Repair Pros of Orange County did the repairs.











The white Aquaplas covering isn't that obvious, through the grille.

 

[nasinn]

...another L65A owner here. Are you planning to do any upgrades to the crossover?

Hallo Hannes, thanks for you kind words. To answer your question, yes that is on the long term plan, I did some strange measurements as seen above and also in the post below linked below:

https://audiokarma.org/forums/index...r-checking-measurement-vs-simulation.1023524/

There I got the recommendation to change some select caps regardless of any measurements, which I might do once I figure out which replacements are suitable. I also liked the idea of doing one at a time to try to listen for any changes.

Hope that helps,
Jonas

 

[nasinn]

The Woofers and all else look super! Bravo!

Thanks markd51, your input was good leading up to it!

 

[nasinn]

Yeah. My L166 find had the woofers messed up like that. I went with cone and voice coil. The Aquaplas was applied onto the front, as the cones aren't made anymore with the Aquaplas on the back from JBL. Sound seems okay.
Speaker Repair Pros of Orange County did the repairs.

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The white Aquaplas covering isn't that obvious, through the grille.

Those look nice, I also like the white. I had never heard of the L166, they look pretty wild! Those Orange County guys seem to have done a good job.

I am not sure that is the same sort of white adhesive thing that I was confused by, the simply speakers instructions only mentioned applying on the surrounds,

as can be seen around 38:22. But yeah, I will just see if it holds up for the next few years!

 

[Mr Boochie]

Those look nice, I also like the white. I had never heard of the L166, they look pretty wild! Those Orange County guys seem to have done a good job.

I am not sure that is the same sort of white adhesive thing that I was confused by, the simply speakers instructions only mentioned applying on the surrounds,

as can be seen around 38:22. But yeah, I will just see if it holds up for the next few years!

I had all my JBL speakers reconed (back before JBL had surround kits) --- at Orange County Speakers or a tech in North Hollywood that was an authorized JBL speaker repair tech . Speaker Repair Pro is run by the son of the now-defunct speaker repair unit of OC Speakers.