JBL L112 - Crossover Confusion

[boputnam]

Bo.....that's what I said too....at least I thought I did.

OK. Whew...

This:

The 128H woofer in the L112 is a "positive to black" terminal woofer.

So that preceding quote is, unfortunately...incorrect....Sorry Bo

was at-odds with:

Therefore, on the crossover schematic the black/grn wire goes to the black terminal on the woofer; solid green wire goes to the red woofer terminal.

this last quote, being a correct statement.

As designed, the cabinet would be connected with amp output (+) connected to the Red cabinet terminal, which traces to the GRN wire to the 128H (+). Thus, the woof is going to have cone "in" movement on (+) signal (i.e., it is a negative polarity transducer as you noted).

As we know from later dated JBL Tech Notes on JBL's (unique) polarity convention, JBL has since recommended that this vintage of cabinet be connected with amp (+) connected to Black cabinet terminal so that the woof will have cone "out" movement on (+), as is current industry convention. This "reversed" cabinet connection will reverse the absolute motion of all the transducers, while maintaining their relative polarity (crucial for matching the crossover design).

The most important thing here, faithful readers, is to follow the wiring color code on the network schematic - only by these connections will you maintain the crossover (and cabinet) design characteristics.

[opimax]

OT a little, pardon me

I got a little confused when changing XO on my 250

What about on a 4 way XO ? maybe another day

Someday I need to verify (understand) the original 250 and the ones Guido built to make sure I do have them hooked up properly...

I understand enough to keep my woofers all firing out at the same time but not checking individual connections at the XO

Mark

[brudha]

When you open a vintage JBL cabinet the woof is connected non-BLK to Red terminal, that is, solid color (non-BLK) to Red - always. I don't work on raw drivers like you do, but I have opened dozens of un-tampered cabinets and it's always the same - absolutely consistent. The scheme is steadfast. Any wire with anything "BLK" goes to the black terminal.

This wiring diagram of the L220 woofer (LE14H) looks to be the opposite of your statement. It shows the Green/Black going to the RED post and the solid Green going to the BLACK post. I could have sworn when I took them out that the Green/Black was on the Black post. Now I'm all confused........

[4313B]

Here's a couple more to add to the fun:

L112 and L220 (alnico)

[brudha]

Here's a couple more to add to the fun:

L112 and L220 (alnico)

Those pics still show the black-striped wire going to the black post though.

What's the deal with the L220 LE14H being the reverse, in that, the green/black goes to the RED post? Is it possible it's a typo in the original manual? Like I said, I'm reasonably certain the green/black was on the black when I removed them. Now, upon reinstall I'm not sure how to proceed..........

[4313B]

Is it possible it's a typo in the original manual?

Absolutely.

In any case, you should be able to tell which way sounds correct.

I'd start with solid green to the red terminal on the LE14H.