View Full Version : 4311 crossover issues ?

07-07-2003, 08:14 PM
Greetings from a newbie,
Forum looks very interesting, with the correct amount of attitude when required !
I have owned a pair of 4311WX-A Monitors. After years of putting up with imaging problems IWhat I finally did was relocate the mid and tweeter on one box to be mirror image ala 4312. it has helped, I still wonder why they weren't built like this originally?
Here's the latest dillema. My 4311's are getting their crossoverschecked over as anything with caps in it have a way losing their values after a decade or two. So after extracating them from the cabinet, I was shocked to figure out that the woofer is running as a full range driver ! My Questions are these.
Has anyone tried limiting the frequencies that are sent to the woofer ? What kind of results could I expect?The mid range takes over from 1.5khz. What value low pass coil be appropriate for this application ?
What's all this, about "negative polarity" issues with the speakers ?Someone please straighten me out on this. Am I to assume that JBL had a sense of humour or was the Coffee Truck honking outside the factory, at the wrong moment for the consumers!!??
Input would be appreciated , Thanks Dan MacLean

07-07-2003, 08:43 PM
Hello Dan

I was shocked to figure out that the woofer is running as a full range driver !

Yup that's the way they ran them up to the 4312. The 44XX 12" monitors had them set-up the way you would expect. That's the way they were designed. You can play with the crossovers but you will change the character of the speaker.

What's all this, about "negative polarity" issues with the speakers ?

JBL was opposite from the norm positive voltage on the neg equals forward movement. JBL has a polarity document in the tech article part of the Pro Site.


07-07-2003, 08:43 PM
...doesn't sound so. ;)

Hey, Dan -

Yup, the 4311 LF transducer is seeing full range, identical to the 4312 series. That was design, then. Surely Giskard, Widget or others here will know the engineering behind that.

Here's a Link to the 3111 Network - you can see it for yourself: http://www.jblproservice.com/pdf/Network%20Schematics/3111%20Network.pdf

As to polarity - there's some stuff compiled here that discusses this issue. Maybe you've found it: http://www.audioheritage.org/vbulletin/showthread.php?s=&threadid=9

JBL early-on adopted a convention opposite to the one finally adopted by industry. JBL is predominantly "negative" (cone in on positive signal) - see: http://www.jblpro.com/pub/technote/tn_v1n12b.pdf

This doesn't matter unless you were inclined to swap out the 2212H (negative) for a 123A (oddly, positive), then you'd need to wire GRN to Black terminal to maintain the intended cabinet polarity (i.e., the designed phasing with the MF and HF). The only other time it matters, is if you are pairing vintage JBL cabinets with any other brand - the JBL's will be out-of-phase, and you'll get cancelling.