I've never seen a C35 that was cut for a 12-inch driver. Every one I've seen, or have, was designed for a 15-inch and you ordered adapter plates to fit anything smaller. I'd guess at home-built but I'd like to see better pictures of the back in-place to be sure. Regardless, it looks nice and solid.
". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers
What would the back tell you? I'm not sure it is original because there is no place for a crossover like the N2400 or N2600. I modified it probably 20 years ago to accept some spring clip terminals too.
It's easy to compare the quality and technique of construction by looking at the fitting of the rear panels. JBL made the cabinets both in plywood and particle-board but the style and fit of the rear panel for me has always been the easiest way to tell a home-built.Originally Posted by Yardstick
Doesn't really matter in your case since it's pretty obvious it's not a JBL cabinet.
". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers
How can you tell it's not a JBL cabinet? I thought the lock mitre joint suggested it might be, but I know that's not an exclusive construction technique. The front and back are MDF.
Most baffles in that era are not MDF. I say it isn't a JBL because they just didn't make one that size that I'm aware of.
". . . as you have no doubt noticed, no one told the 4345 that it can't work correctly so it does anyway."—Greg Timbers
These do seem small compared to a lot of the cabinets that would have had drivers with 16 Ohm labels. I calculate about 2 cubic feet, which is too small according to the 1960's enclosure manual. Maybe those Calrad crossovers were part of a kit. The other crossovers don't have much for indicating marks other than the year. The three coils and all the wires coming out of them suggest they are a 3-way design. Were there other brand name speakers using JBL drivers in that era? Any other way of tracing a kit? I might pull all the fiberglass and see if there are any other markings underneath. It would probably be better to have a synthetic or cotton batting in there anyway.
My current strategy is going to be:
1. Make an N2400 Crossover copy (parts incoming).
2. Modify the existing baffle with a 5" duct on the existing port (also closing the port down slightly).
3. Mount the drivers and hear them play!
If I like what I hear and I want to hear more, I'll modify the crossover as needed and maybe make new, larger volume enclosures.
There were all sorts of companies making generic cabinets and crossovers back then. This isn't a "kit" it just the way people put together speaker systems back then, usually from a catalog. It looks like someone back in the 70's upgraded the crossover, which is a good thing. Just because a crossover has three coils doesn't mean it's a three way. If you trace out what's going on in the crossover I could tell you what you have. It looks like high quality stuff. I've also never heard of or seen a stock JBL cabinet with a 12 inch opening. You have a nice little vintage two way system, why not just enjoy it? There's only so far you can take that driver set.
That makes sense. I wish I knew more about these speakers or had a resource like this when I got them. I ran across a 2-way crossover with three coils a few hours after I posted. I'd almost have to disassemble that crossover to figure it out. I could trace the circuit, but I can't see what the capacitor values are. That also makes it tough to figure out how they should be hooked up. Both crossovers are old and a significant departure from the N2400. I think I bought better parts for my N2400 copy too (based on this thread). Now that I have the parts I can build the crossover I need. If all goes well I may just refresh the front and rear panels, make grilles and clean up the cabinets the best I can. Since the cabinets are pretty beat up and they are a little too small, I might take it a step further and build new cabinets with increased volume. One step at a time.
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