Thanks guys. Much appreciated.
Also discovered during my testing why I was seeing that large turn on exotherm. JBL uses a NTC thermistor in the bias network to head off thermal runaway of the...
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Thanks guys. Much appreciated.
Also discovered during my testing why I was seeing that large turn on exotherm. JBL uses a NTC thermistor in the bias network to head off thermal runaway of the...
My L212 sub amp starting sounding weak (lower output at the same sound levels for the satellites), and after having an Al electrolytic failure in one of my TEK 576 curve tracers (which use the same...
I rebuilt the crossovers in my L212 using Dayton polypropylene film caps and it sounds great. I did use values as close as possible to the originals (within 5 - 10%). IMHO polypropylene films sound a...
Pull the cover plate (two screws on the front and a number underneath) and look. The power supply caps are the four large silver cans sticking out of the board. Don't attempt to remove these without...
I am in the process of repairing/upgrading my L212 bass energizer as well. I am using 4 x 27,000 mfd Panasonic 63V THA caps on a separate PC board, and an outboard bridge rectifier. Removal of the...
You can but need to provide the EQ for the driver. Look at the feedback loop in the original. Was considering this route for my L212 bass unit, but considering the added complexity of summming L and...
Along these lines, maybe the coupling capacitor failed short (unlikely, but possible) and there is an excessive amount of low frequency energy being fed to the driver?
Mr. Widget:
Actually, the JC1/JC2s make my L212s sound amazing. Brings them up to the levels of my B&W 803ds which cost almost 10X the JBLs (maybe less than that in today's $). I was amazed at how...
I vote for the air core inductors. Yes they are big. Yes, they are heavy. Yes they are expensive. But they sound better than iron core alternatives and I don't want to worry about exactly what power...
Thanks.
I just hooked them up to my reference system (Cambridge Audio CD/Bryston BDA-1, Parasound JC2 line preamp, JC1 monoblock power) and disconnected my B&W 803ds.
WOW is all I can say....
You can get both the boards and "turrets" from
http://www.tubesandmore.com/
Look under "Hardware and Terminal Items", then "turret boards". Both the boards and turrets should be listed. Note...
I agree with other posts that removing the grills will sound best. Esp if the grill material was not provided by JBL, but an EBay seller. Who knows what the acoustic characteristics are?
I am...
I think we went round and round on crossovers for the L212 sometime back. All I was able to determine was that the main components were pretty much the same for all versions, except for some changes...
The simplest method to use, without a lot of experimentation, is to align the rear of each cone (or the spider position) to the same plane. That should get you pretty close. I had a pair of L100s (or...
After many years of collecting dust, I have finally completed the restoration and modification of my JBL L212 system. It was originally purchased by me in the late '70s. After many hours of sonic...
Yes, that is still the goal. Building new cross overs. I was checking the values in the published schematic to see if they matched the published spec of cross over points of 800 Hz and 3000 Hz. If...
4313B: "Too bad. That could have been fun. You could have whipped up some nice 24 dB/octave LR active filters, put some nice little amps behind them and possibly ended up with something rather...
Sorry, I don't have either the L-pads or the cross overs.
If this is true, then what were the "standard" resistive loads used as substitutes for the drivers? 8 Ohms? If you use 8 Ohm resistors you will not get the response in the 1977 plots with the values...
Please look at the attached data:
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=17989&stc=1&d=1157029720
This is a voltage (not SPL acoustic) BODE diagram of the L212...
I have never heard of the term "acoustic crossover" when discussing passive component crossovers. Every design guide and speaker building document refers to the electrical cossover points in the...
You can also use "TAG" boards, that are popular with the tube amp builders. These are already built as you suggest, with a parallel row of pins.
See, for example,
...
I just got schematics via EMail from HCG customer support. I also was able to see the tech papers posted here under the technical info section for the L212.
The one "error" that I note between the...
I like to use the products containing beeswax and lemon/orange oil. This product has a paste like consistancy and is easier to apply on vertical surfaces than a straight oil. You wipe it on like a...
I am restoring my L212 speakers, and I need the schematics for the cross over networks. I tossed the crossovers years ago when I was planning to tri-amp the L212 with active cross overs, but never...