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JBL 4312c

M

mewoods

New Member
Just picked up a pair of, kind of rough, JBL 4312c's for super cheap. Any tips on what to check to see if they are viable for use or just door stops? I don't have an amp to hook it up to other than a cheap Sony 5 channel home theater receiver. Pretty sure it wont drive the JBL's very well. ;)
 
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I have two pair of 4312C's--both studio black, but one pair is early production with the 2213 AlNiCo woofers and the other, later production with the 2213H ferrite woofers--ask away!!! Biggest thing is to make sure all drivers work and clean the L-pad pots.
 
savatage1973 said:
I have two pair of 4312C's--both studio black, but one pair is early production with the 2213 AlNiCo woofers and the other, later production with the 2213H ferrite woofers--ask away!!! Biggest thing is to make sure all drivers work and clean the L-pad pots.
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Is there a way test the drivers other than just plugging into an amp. Any way to check/test the crossover? The boxes are a wreck but I picked then up for next to nothing so great place for me to start off my audio tinkering. If electronics check out I am a cabinetmaker and can replace or improve upon the boxes. I know most would probably want original mint condition examples but I am not looking for collectablity; more so functionality. My 15 year old saw them and asked if she can have them in her room. From what I read seems they would be great near field for her small room but maybe a little loud when driven with 100 watt amp?
 
Good taste. She will surely have better sound than her contemporaries whose "hi-fi" is ear buds or little blue tooth speakers. Nice going.
 
They are a very flat and very honest monitor speaker. The good? They will reproduce anything that goes in. The bad? They will reproduce anything that goes in (garbage in = garbage out).

Pair them with a nice quality amp or receiver in the 50wpc range and you'll have more music than she needs. If all six drivers work, chances are that there's no problem with the speakers, they are pro monitors and can take a lot of grief provided it isn't clipped to hell.
 
They will sound very rich on a tube amp and there quite efficent so no need for big power.Mine sounded great as near field monitors in a bedroom system with a pair of Dynaco mkiv monoblock amps and a pas 2 preamp
 
mewoods said:
My 15 year old saw them and asked if she can have them in her room. From what I read seems they would be great near field for her small room but maybe a little loud when driven with 100 watt amp?
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In a small bedroom, 100 WPC would be overkill. A small vintage receiver will give her more than enough power to drive them. I'm currently driving a pair of L36 Decades in a small bedroom with a 14 WPC Sherwood S-7100A and it sounds great.

In addition to the Sherwood, something like Pioneer SX-424 or SX-525 or a Sansui 221 or 331 would work well in small bedroom.
 
How did the test go? Got pics?

The L-pads for mids and tweeters often get dirty/scratchy or develop a "dead" spot. Give them a good twisting (20 rotations?) before declaring a mid or tweeter dead.
 
mewoods said:
Is there a way test the drivers other than just plugging into an amp. Any way to check/test the crossover?
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Actually, just plugging them in and trying them is the simplest and easiest way to test them--otherwise, you can pull each driver and measure with a DMM the DCR and continuity (or lack thereof). The two potential issues with the crossovers are the L-pad pots and ageing electrolytic caps--work the pots and they should be fine, the caps are another project for when you are feeling "frisky"--the XOs are kind of a PITA to get out--you have to carefully remove the foilcals to get to the screws or just order new reproductions (available on that auction site, but not necessarily cheap).

Another tip/trick with those big old white JBL woofers is to rotate them 180 degrees to re-center the VC--if not used regularly or not stored under decent conditions, they can "sag" and develop a voice coil rub that can generally be corrected by rotating the woofer and letting gravity do the work.
 
Haven't hooked them up yet. I only have that super thin speaker wire that came with a Sony surround sound system. Going to give it a go tonight regardless. Will post pics but boxes are kinda rough. I'm a cabinetmaker so not too worried about the need to improve or replace the boxes of electronics function as should.
 
Here they are. Hard to see the damage but boxes are scratched up and some damage to the bottom panel. Looks like may have gotten wet and swelled the area around the dado for the back. Hoping the electronics haven't suffered. Grill cloth is remarkably in pretty good condition. No pulls or tears.
 

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Set up and all the drivers are working! Xo's too. Crappy Sony surround sound amp with dental floss speaker wire but that will change soon. XO pots are a little scratchy but not overly worried about them. Did rotate them a number of times as suggested. Initially, in my haste, plugged in my iPhone and played mp3's haha. Now listening to cd's through another inexpensive Sony CD player. Not hi fi yet but Mark Knopfler One Take Radio Sessions sound MUCH better through this set up than what I have been listening to. Next? Amp, cables, dac, turn table, speaker stands and proper CD player. Possibly even in that order.
 

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Most JBL's are efficient enough to sound very good with small wattage.
My little Scott 15watt tube amp works well with some L-101's and a 35watt Luxman receiver takes it to party volumes even.
I found mine a few months ago for $20 and put a little work into them and am a new JBL fan as well. They are just so easy to listen to for hours at a time and never feel like you;re missing anything in the music.
Now I understand why people love these "old" heavy wood speakers.
Good looking out Pop!
Your daughter will love you forever for the classic improvement to her favorite music!! :banana:
 
mewoods said:
Here they are. Hard to see the damage but boxes are scratched up and some damage to the bottom panel. Looks like may have gotten wet and swelled the area around the dado for the back. Hoping the electronics haven't suffered. Grill cloth is remarkably in pretty good condition. No pulls or tears.
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Not as "rough" as you implied--go spend $3 on some Kiwi Black Shoe Polish and buff them out--you will be pleasantly surprised.
 
All driver working...that is sweet :thumbsup:

You can spend a whole lot of $ and do a lot worse on quality.
 
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