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JBL L100 Restoration

bzowk

bzowk

New Member
Hey Guys -

I'm planning on restoring my old JBL L100's that my father gave me long ago, but wife put me on a budget. I wish I had taken better care of them when younger as they are in rough shape and been through a lot. I'll definitely have to re-cone the woofers and refinish cabinets, but wanted to ask a few questions if i may...
  1. What is the best method to test individual drivers to see if they need to be re-coned? (specifically the tweeter & mid-range)
  2. I've found this re-cone kit, but am still shopping around since on a budget. Any suggestions or suggested sites to save money yet maintain quality for these kits?
  3. I've seen multiple articles with people rebuilding the crossover for them. Seems "Dennis Murphy’s L100 Crossover Upgrade" seems to be the best for money. From experience does anyone know if something like this would be worth the cost?
  4. Finally, once restored I want to build a system to drive them which also has enough power. Having endless computers & parts, I'm planning on setting up a touchscreen device. Anyone suggest a DAC / Amp which would be ideal for this? Was looking at HiFiBerry DAC2 Pro, but assume I'd need an amp in addition which could get pricey fast.
Suggestions appreciated - Thanks!
 
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L100s don’t need much power, that should be easy.

Why do you feel that they need new cones?

BTW, this would probably be better in the Lansing forum, click on REPORT and ask a mod to move it if you wish.
 
To test the speakers, just hook them up and listen. There is a good chance that the level controls are corroded, so you may need to spray some Deoxit D-5 inside them (I think you need to remove the woofers and spray into the back of the pots; it's been a while since I was inside mine). Even if the crossover capacitors are leaking, you should still get some sound out of the mids and tweeters. Are the drivers visibly damaged? These JBLs are pretty tough. Torn cones can be glued, dust caps can be undented or replaced.

Post some pics of what you're working with so we can better advise you.
 
Thanks Guys...

Good idea & suggestion on the grill covers. Unfortunately, I don't think I know where they are :(. If I cannot find, plan to rebuild or perhaps build them into cabinet like was done here.

I dug one of them out of storage a few minutes ago and here are a couple of pics which I'd think would explain the re-coning and full restoration overall.
L100_1.jpg L100_2.jpg L100_3.jpg L100_4.jpg

There's quite a bit of dust on them, but still obviously have more issues than a cloth can fix...

Thanks
 
Definitely. Know it won't be cheap, but speakers are worth it so wanted to post to see if anyone had suggestions. Planning to follow these steps fairly closely, but wanting to explore all options (especially cost saving ones) before starting. Open to any ideas or suggestions you may have. Thanks
 
Hi I did a similar restoration about 7 years ago on a set I bought on ebay. Love them! Restoration was an investment, but worth it.

For the woofers: I searched and searched for white replacement cones without luck. One voicecoil was in bad shape. I sent mine to Orange County Speakers who were JBL specialists. Their cone came close to the original look. They went out of business, but if you google them I recall one of their employees went out on his own.

Tweeters:. Mine were good, but needed foam surround. Identical versions are available at speaker shops like "Midwest speakers"

Mids: One failed recently and I resorted a working one from replacement from eBay.

Lpads: mine were cooked, literally partially melted. Parts Express has exact replacements.

Crossovers: I rebuilt mine to stock configuration after contemplating several upgrade versions out there.

bzowk said:
Definitely. Know it won't be cheap, but speakers are worth it so wanted to post to see if anyone had suggestions. Planning to follow these steps fairly closely, but wanting to explore all options (especially cost saving ones) before starting. Open to any ideas or suggestions you may have. Thanks
Click to expand...
 
bzowk said:
I'm planning on restoring my old JBL L100's that my father gave me long ago, but wife put me on a budget. I wish I had taken better care of them when younger as they are in rough shape and been through a lot. I'll definitely have to re-cone the woofers and refinish cabinets, but wanted to ask a few questions if i may...
  1. What is the best method to test individual drivers to see if they need to be re-coned? (specifically the tweeter & mid-range)
  2. I've found this re-cone kit, but am still shopping around since on a budget. Any suggestions or suggested sites to save money yet maintain quality for these kits?
  3. I've seen multiple articles with people rebuilding the crossover for them. Seems "Dennis Murphy’s L100 Crossover Upgrade" seems to be the best for money. From experience does anyone know if something like this would be worth the cost?
  4. Finally, once restored I want to build a system to drive them which also has enough power. Having endless computers & parts, I'm planning on setting up a touchscreen device. Anyone suggest a DAC / Amp which would be ideal for this? Was looking at HiFiBerry DAC2 Pro, but assume I'd need an amp in addition which could get pricey fast.
Click to expand...
I built that crossover for my L100a speakers years ago. I highly recommend it, as the original crossovers weren't up to the job.

Someone else recently asked about the Dennis Murphy L100 Crossover. I responded here
https://audiokarma.org/forums/index...-century-crossover-help.957300/#post-14728234

To answer him, I looked up prices and availability of parts for the crossovers. The PDF file I attached in that post explains it all, with schematic diagrams, parts lists, photos and diagrams of the new crossover I built. Unfortunately, prices for crossover parts have gone up. I included some options that can lower the price.

If you do plan on building it, make sure the woofer, mid-range, and tweeter drivers work in your speakers. Test them with the simple AA battery test (explained in the PDF).

Don't worry about those variable L pads – they're probably badly oxidized – and may not conduct any signal to the mid-range drivers or tweeters. The new crossover doesn't use variable L pads at all, as all of them, new or old, are prone to oxidation.
 
You could get in touch with Midwest Speaker in Minnesota. They should still be an authorized JBL repair center.
 
bzowk said:
I'm planning on restoring my old JBL L100's that my father gave me long ago, but wife put me on a budget
Click to expand...

To start not a huge JBL fan, do I appreciate them yes... not my every day speaker.

That being said if these were your fathers speakers... the wifey has nothing to do with your restoration or cost.

Get a marriage counselor... get them restored correctly and enjoy them as your dad did:)
 
I'm not a fan of the L100 but I do own the first pair I ever heard back in 1971, or so. They belonged to a friend and he sold them to me in condition not as bad as yours a couple of years ago. I bought used tweeters off Ebay. The woofers are in good shape. The cabinets will survive. The grille frames are beat but he did buy new foam inserts a few years ago and I have those. Honestly, I understand your sentimental attraction to these but they're not worth your time and money. You'd be better off finding a pair with beat cabinets and intact drivers and start over. At least then you'd have original drivers. But would they still be your Dad's speakers after all that? Probably closer to what he had than rebuilding yours with after-market re-cones. I still have my Dad's JBL 030 system from 1956, so I know how you feel. I didn't take the best care of that speaker over the years but they were tougher and all the drivers still work perfectly. I have JBLs that sound much better, but the 030 was my Dad's and, even though he put it to the curb for Goodwill to pickup when he went to stereo, I dragged it to my room about 50-years ago and still have it today. You are doing your project for sentimental reasons and there's nothing wrong with that. Unfortunately when you're all done, they'll still just be L100s.
 
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About a year later, I have mechanically restored the first pair of L100s I ever heard. And I've now played them for the first time in years, using the appropriate 50th Anniversary Legacy Edition of Miles Davis' "Kind of Blue" for their audition.

I started with this:

52152280644_fb366d55d7_k.jpg


52147003871_d683f2ead7_k.jpg


Ended up with this. Ready to play:

52151050832_b2b3f44771_k.jpg
 
2464FDFA-E1FD-48B1-A6B0-91F990493479.png B11CBC56-A5B2-481E-905D-EC8532BE889E.jpeg This is a work in progress. I’m looking at upgrading to the same crossovers as you however, I rebuilt the original crossovers using high-end caps so as to get used to their sound for a few months first. At some point I will upgrade and see how much difference I can hear.
I bought these knock-off grills that I think look great but, they sound like ****. They cut 3 dB overall and really muttle the mid to high end. Very noticeable to everyone when I pull them off. Once I looked at the construction of them it was fairly obvious. In reality, they would be perfect acoustic wall panels.
Overall I’m pretty happy with the speakers for what they are, a 50 year old speaker design.
 
Jflijohn said:
I bought these knock-off grills that I think look great but, they sound like ****. They cut 3 dB overall and really muttle the mid to high end. Very noticeable to everyone when I pull them off. Once I looked at the construction of them it was fairly obvious. In reality, they would be perfect acoustic wall panels.
Click to expand...
It's okay to let others know where these sound-muffling grilles came from. Think of it as a community service. My repro grilles are unpainted and don't seem to have the same detrimental effect.
 
BMWCCA said:
It's okay to let others know where these sound-muffling grilles came from. Think of it as a community service. My repro grilles are unpainted and don't seem to have the same detrimental effect.
Click to expand...
526CDACC-4FB6-44C5-AB57-79E62F2E139A.jpeg So, I honestly don’t remember where I got them but (I just saw quite a few sources on the web listing it as Quadrex) to further my point, this is the back side with a 100 watt equivalent light bulb on the front side. Even photons can’t make it through this super-fiber.
It’s not Huntley Audio.com (as in the photo) they just made the frames. I’m replacing these with the Huntley Audio.com cloth grills. Not data yet.
 
Jflijohn said:
View attachment 2596994 So, I honestly don’t remember where I got them but (I just saw quite a few sources on the web listing it as Quadrex) to further my point, this is the back side with a 100 watt equivalent light bulb on the front side. Even photons can’t make it through this super-fiber.
It’s not Huntley Audio.com (as in the photo) they just made the frames. I’m replacing these with the Huntley Audio.com cloth grills. Not data yet.
Click to expand...
Judging by the too deep error overcuts that extend out into the border those were made in washington state..how long ago did you purchase them?
 
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