L212 restore

[sweetliberty]

Hi all
Being a JBL freak from way back. L77, L200's, 4350, and finally L212 - never been happy with anything except JBL.
I have just partially restored a pair of L212's. Very happy with the sound although they could do with some fiddling to improve the already great top end.
Some of the knowledgable ones here (and there are plenty) claim that bypass capacitors are the way to go. Others say that charge coupled caps are better. Which one?
The cabinets are very sorry condition - walnut veneer cracked and faded, fabric stained and clips brocken. To much work in building new cabs. Thinking of doing away with covers and filling and painting in high gloss black polyurathane paint.
Feedback please.

[Zilch]

http://audioheritage.org/vbulletin/showthread.php?t=3555

Current top of the line JBL uses biased Solens.

[Zilchster, too.... :p ]

[sweetliberty]

Thanks zilch however I just replaced the original caps with solens. Charged coupled or bypassed caps? What do you think?
I love these speakers but there is room for improvemnet.

[Zilch]

Solens don't need bypassing.

Your next comprehensive crossover improvement is going to come via biasing.

There's also a problem that may require fixing. They were designed using a 2 pi hole in the ground for measurements. There were consequences:

http://www.audioheritage.org/html/perspectives/smith.htm

I'd have to research whether that was ever addressed. Giskard recalls being shown a notch filter "fix." I'd guess only he could answer that question, or obtain the answer.

There's five caps to bias:

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/L212%20ts.pdf

I just did a similar with four. Ain't gonna be cheap:

http://audioheritage.org/vbulletin/showthread.php?t=14674

Rethink your plans for the cabinets: consider rebuilding them mirror-imaged, a significant improvement. There's a thread here on that, I believe....

[sweetliberty]

Thanks again zilch.
That circuit diagram is most usefull.
They sound a little "nasel" on male vocals. Like a singing through a 3" tube. Turning down the le5 midrange improves this but at the cost of the rest of the midrange.
What do you mean "using a hole in the ground"?

[Zilch]

What do you mean "using a hole in the ground"?I just added the "Hole in the ground" reference link in the post above. :thmbsup:

That may be what you're hearing. Again, I don't know if it was ever fixed in production....

[sweetliberty]

OK I just read the link.

[Zilch]

I don't mean to discourage you with this project, but if you like that configuration, consider Performance Series if they are available to you. Some members are finding them at deep discounts in the U.S. lately.

Johnaec brought PT800 by here for me to measure. Their clarity is stunning.

On the other hand, Giskard may have some ideas regarding repackaging what you presently have. You'll have to wait until he has an opportunity to get back to these forums to help out, tho.

There are some other members who have "redone" L212s. You might want to allow some time for them to post on these subjects as well before deciding how to proceed....

[sweetliberty]

Zilch much apreciated. I will keep an eye out for them
Thanks again.

[MJC]

I don't mean to discourage you with this project, but if you like that configuration, consider Performance Series if they are available to you. Some members are finding them at deep discounts in the U.S. lately.
There are some other members who have "redone" L212s. You might want to allow some time for them to post on these subjects as well before deciding how to proceed....
I'm one of those people who have managed to get the PT800s for cheap, and I do have them in my HT and also get used for DVD-A/SACD. They're very nice.
On the other hand, having a pair of mirror imaged, CC L212s is nothing to turn your back or ears on. I currently have them connected to Citation pre-amp/power amp setup with a turntable as the source. Once again, very nice.
I also have another pair of L212s, in this room, mounted on the wall, connected to this computer, dvd player thru a Marantz receiver. This pair has a by-pass xo.

[Zilch]

Hi, MJC.

Aren't there threads illustrating mirror-image cabinets and biased crossovers for L212?

Could you link them here for reference, please?

I'm still tracking down a Giskard design....

Edit: Not the specific one I was looking for, but here's some ideas for similar configuration:

http://audioheritage.org/vbulletin/showthread.php?p=147625#post147625

http://audioheritage.org/vbulletin/showthread.php?p=147642#post147642

[MJC]

Hi, MJC.

Aren't there threads illustrating mirror-image cabinets and biased crossovers for L212?

Could you link them here for reference, please?

I'm still tracking down a Giskard design....
I don't know that there were any pictures of mirror L212, except what I loaded onto my old computer.
But here is the link to the CC schematic: Post # 9

http://audioheritage.org/vbulletin/s...ht=Biased+L212 (http://audioheritage.org/vbulletin/showthread.php?t=5433&highlight=Biased+L212)