DingDing
03-03-2015, 02:19 PM
Imagine for a second that you're teaching a toddler to work out this puzzle box
http://imsdm.scene7.com/is/image/imsdm/031254?$osaMain$
Now replace the toddler with me, the box with JBL 4343B and the pieces with wires and polarity but keep the same mindset, we good? :D
Ok, so on to the issue here. I own a pair of 4343B with charge coupled network and passive xover between (mid, hf and uhf). The lf driver (2235h) and the rest requires active xover. The rear of the speakers has two sets of terminals, one pair for the lf and one pair for the mid, hf and uhf drivers.
1) I'm going over the polarity of the system and I hooked up a 9V battery to check the polarity of the woofer. Connecting the speaker terminals to a 9V battery, Red to + and Black to - made the cone go inwards. Since the speakers will be used together with subs where Red to + and Black to - made the cone move outwards I need to make some adjustments.
2) I did not do a polarity check on the (mid, hf and uhf) wired to the network as I was afraid I might damage something, and I wouldn't know how to see the polarity of the hf and uhf drivers anyways.
3) Since the speakers require an active crossover they also require four channels.
4) I assumed it would be as easy as (Amplifier Red to Speaker Black) and (Amplifier Black to Speaker Red) but then I came across this post in the forums http://www.audioheritage.org/vbulletin/showthread.php?9-JBL-Polarity-Convention&p=30&viewfull=1#post30
If you are going to reverse the polarity of a JBL cabinet, it must be done AT EACH COMPONENT in the cabinet. You should not simply hook-up the cabinet red-to-black. That will not have the proper effect, because that will result in the signal being pathed through the transducer before the capacitor(s) - this is a DC circuit, and that is backwards. For the crossover network to work properly, the capacitor(s) must see the signal BEFORE the transducer, regardless of cabinet (and transducer) polarity.
To "correct" or re-phase a vintage JBL cabinet, you need to reverse-wire at each component. Simply alter the signal path AFTER the crossover and before the transducer, at each component binding posts.
As example, if your cabinet is out-of-phase (negative), and woofer is wired GRN-to-red post, switch the woofer to GRN/BLK-to-red post. Reverse the wiring for EACH component (this will ensure the mid-range stays 180-degrees out-of-phase in 3-way cabinets). The woofer - and cabinet - will then be positive, and industry standard.
It is handy - but not necessary - to review the network schematics, if you're so inclined, and yours is available:
Link: http://www.jblproservice.com/pdf/Network%20Schematics/
A) So now I'm not sure what to do? I can't do as I assumed in point #4?
B) Should I and how would I go about making the speakers adhere to the current industry standard, please?
PS: I did read the polarity convention of JBL transducers and systems pdf, but again, refer to the puzzle box, please. :D
http://imsdm.scene7.com/is/image/imsdm/031254?$osaMain$
Now replace the toddler with me, the box with JBL 4343B and the pieces with wires and polarity but keep the same mindset, we good? :D
Ok, so on to the issue here. I own a pair of 4343B with charge coupled network and passive xover between (mid, hf and uhf). The lf driver (2235h) and the rest requires active xover. The rear of the speakers has two sets of terminals, one pair for the lf and one pair for the mid, hf and uhf drivers.
1) I'm going over the polarity of the system and I hooked up a 9V battery to check the polarity of the woofer. Connecting the speaker terminals to a 9V battery, Red to + and Black to - made the cone go inwards. Since the speakers will be used together with subs where Red to + and Black to - made the cone move outwards I need to make some adjustments.
2) I did not do a polarity check on the (mid, hf and uhf) wired to the network as I was afraid I might damage something, and I wouldn't know how to see the polarity of the hf and uhf drivers anyways.
3) Since the speakers require an active crossover they also require four channels.
4) I assumed it would be as easy as (Amplifier Red to Speaker Black) and (Amplifier Black to Speaker Red) but then I came across this post in the forums http://www.audioheritage.org/vbulletin/showthread.php?9-JBL-Polarity-Convention&p=30&viewfull=1#post30
If you are going to reverse the polarity of a JBL cabinet, it must be done AT EACH COMPONENT in the cabinet. You should not simply hook-up the cabinet red-to-black. That will not have the proper effect, because that will result in the signal being pathed through the transducer before the capacitor(s) - this is a DC circuit, and that is backwards. For the crossover network to work properly, the capacitor(s) must see the signal BEFORE the transducer, regardless of cabinet (and transducer) polarity.
To "correct" or re-phase a vintage JBL cabinet, you need to reverse-wire at each component. Simply alter the signal path AFTER the crossover and before the transducer, at each component binding posts.
As example, if your cabinet is out-of-phase (negative), and woofer is wired GRN-to-red post, switch the woofer to GRN/BLK-to-red post. Reverse the wiring for EACH component (this will ensure the mid-range stays 180-degrees out-of-phase in 3-way cabinets). The woofer - and cabinet - will then be positive, and industry standard.
It is handy - but not necessary - to review the network schematics, if you're so inclined, and yours is available:
Link: http://www.jblproservice.com/pdf/Network%20Schematics/
A) So now I'm not sure what to do? I can't do as I assumed in point #4?
B) Should I and how would I go about making the speakers adhere to the current industry standard, please?
PS: I did read the polarity convention of JBL transducers and systems pdf, but again, refer to the puzzle box, please. :D