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roundnyellow
09-12-2003, 09:44 AM
I recently picked up a set of l212ís at a yard sale, $30.00. Looks like they need new surrounds, sub woofer new cone, tweeters have small dings. Iím very new to the audio world so please have patience. Each speaker has a rheostat and what I guess is a filter bank, they look like theyíve shorted (burnt connections on stats.

Iíve little written about the 212ís. Are worth rebuilding? Are they something I can build a good system around? If I do have them refurbished what should I look out for and how much should I spend?

Thanks,
Gary

Speakertown
09-12-2003, 10:00 AM
That's a good buy at 10X what you paid! Yes, by all means
do those inexpensive repairs. Do no run the woofers until you
get them re-foamed. They may need new cone kits, depending
on the voice coil's condition. The dented tweeters should be
fine unless the coils are also tweaked and rubbing.

Those "reostats" (actally L-pads) are very inexpensive,
like $5. ea. (for genaric), so by all means replace them. Make sure to
get the same ohmage (4,8, or 16), and use 50-100 watt
units.

Those in good cond. are probably worth around $1K.;)

Oops, I should have offered you $100. for them..... rats!:p

boputnam
09-12-2003, 10:56 AM
Originally posted by roundnyellow
Iíve little written about the 212ís. If no one's posted this, here's a L212 - Link (http://www.lansingheritage.org/html/jbl/specs/home-speakers/1977-l212.htm) that will give some more reading material.

I do believe that a one Giskard has a set of these - if he hasn't responded already, he might be off enjoying them... ;)

roundnyellow
09-12-2003, 11:07 AM
Thanks for the info. should I look for a JBL certified repair shop? Do you know of one in the SoCal area.

Once again thanks,
Gary

boputnam
09-12-2003, 11:37 AM
Originally posted by roundnyellow
a JBL certified repair shop ... in the SoCal area. Hey, Gary...

Yea, the Orange County Speaker - Link (http://www.speakerrepair.com/) is highly recommended (even by JBL Pro ;) ). Maybe you can drive over and hand deliver the babies. Or, you can get some surrounds and do the work your self! It's Fun :nutz:, it's rewarding :banghead: it'll impress the whole family! :bash:

Insist on JBL parts, only, is my opinion. No other maker allowed. Period.

So, pleasure us JBL voyeurs with some pics of the trio, hey? That is one sweet deal you got! :coolness:

roundnyellow
09-14-2003, 10:18 AM
Iíve downloaded the spec sheets. Now, remember I, m new to this, what tells/shows me the speaker input requirements. I would like to build a vintage system with components made the same year the 212ís came out. Am I right to assume itís best to over size.

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4313B
09-14-2003, 11:00 AM
Originally posted by roundnyellow
Iíve downloaded the spec sheets. Now, remember I, m new to this, what tells/shows me the speaker input requirements. I would like to build a vintage system with components made the same year the 212ís came out. Am I right to assume itís best to over size.

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The original L212 system with alnico magnet transducers was rated to handle 75 watts continuous program (Hence, amplifiers rated up to 150 watts per channel). The later versions with the ferrite magnet transducers were rated for use with amplifiers up to 300 watts per channel. In all cases, the systems had a sensitivity rating of 91 dB SPL with 1 watt input at 1 meter.

I'm not sure what you mean by oversizing.

For me the biggest issue with restoring a pair of L212's is getting the 066's back in shape. JBL has very few of these diaphragm kits left and they are all quite old (less than twenty at last count). Once these kits are gone, the 066 is no longer serviceable. In addition, a few of the kits I recently looked at had the vapor desposited aluminum starting to flake off. I would recommend that if you do get the 066's back in shape that you rig up some way to protect the domes.

The original L212 used an inverted paper dust cap on the LE5 midrange transducer. Get rid of it and replace it with the black coated aluminum dome.

The 112A/112H 8-inch low frequency transducer now uses a smooth cone similar to the larger 10-inch transducers.

http://www.audioheritage.org/vbulletin/showthread.php?threadid=481

A single B212 Ultrabass is pushed to it's limits reproducing today's media. Although it is a pretty decent design, it simply doesn't have the effective cone area and excursion required to adequately handle program material recorded today at higher volume levels. Used in multiples and spaced closely together to ensure mutual coupling, the 121A/121H transducers in 2.0 cubic foot sealed enclosures are still a very viable VLF solution for medium efficiency systems.

4313B
09-14-2003, 01:13 PM
Attached are the three A212 side panel schematics.