View Full Version : JBL C70 Alpha I - crossover?

12-07-2008, 07:04 PM
Hi All,
I 've been reading literally hundreds of posts on here this past week. Great community on here!

I have a small project restoring a pair of C70 Alpha I. I haven't been able to track down any info regarding the crossover network for this one. Does anyone know what the original one was for this unit?


12-07-2008, 08:19 PM



12-07-2008, 08:37 PM
BMWCCA, that is the right network model number but I think JBL has the wrong schematic in that Technical Manual. The schematic JBL shows is for the newer LX30 as used in the S21 LCS system.

I think this is the correct link:

#17 (http://audioheritage.org/vbulletin/showpost.php?p=5586&postcount=17)

#18 (http://audioheritage.org/vbulletin/showpost.php?p=5588&postcount=18)

12-07-2008, 08:54 PM
BMWCCA & 4313B:

Thanks for your help :D

12-07-2008, 09:01 PM
Wow! Not even close. More like an N100 w/ wide-open 123A?
Strange mistake in the tech sheet. Not that I ever know what I'm talking about.
Thanks for the correction. :)

12-08-2008, 06:09 AM
Strange mistake in the tech sheet.Yes it is.

Here is where the LX30 that the tech sheet schematic shows is used:


124A, LE5-2, 077 (2203A, 2105, 2405)


124H or LE14H, LE5H, 077 (2203H, 2105H, 2405 or 2405H)

12-08-2008, 12:42 PM
Hi guys,
I'm a bit of a newb when it comes to restoring JBLs, so bare with me please. :D

For reference, is this the one I'll be needing to hunt for preferably used? Are these crossovers hard to come by?

http://cgi.ebay.ca/Vintage-JBL-LX30-Hi-End-Speaker-Crossover-NIB-3-Way_W0QQitemZ220316534299QQcmdZViewItemQQptZLH_Def aultDomain_0?_trksid=p3286.m20.l1116

The C70 cabinets are in excellent shape; just a quick light sanding and oil to restore the glow. I may need to "borrow" a couple drivers from my 4311s to get these up and running, but the quest for crossovers is first.

12-08-2008, 01:23 PM
For reference, is this the one I'll be needing to hunt for preferably used?No, that is the LX30 for the S21 system.
Are these crossovers hard to come by?Quite rare.

You can build the crossovers you need by yourself since I've provided you with the schematic.