L300 Woofer Phasing

[audiomagnate]

I picked up a beautiful pair of L300's last night and was surprised by the weak bass. A quick battery test revealed that one of the woofers were wired out of phase. The 136A's themselves are wired backwards - they move inward when the positive terminal of the battery is connected to the red terminal of the woofer - which I understand is normal (although a little bizarre IMO). I've got the woofers back in phase and the bass is correct, but my question is, what is the proper way to wire these up? Should the black wire from the crossover go to the black terminal of the woofers? This would result in the woofers moving inwards with a positive pulse.

What was the logic of JBL wiring their woofers backwards back then anyway?

[Odd]

61046

61047

[audiomagnate]

61046

61047


I've seen both of those. None of them make it clear.

[Robh3606]

The JBL way is the Green wire to the Red terminal on the woofer. If you start flipping the driver polarities arround you have to address how the other drivers are wired.


http://www.jblpro.com/BackOffice/ProductAttachments/JBL_TechNoteN1V12C_v5.pdf


Rob:)

[DavidF]

I picked up a beautiful pair of L300's last night and was surprised by the weak bass. A quick battery test revealed the woofers were wired out of phase. The 136A's themselves are wired backwards - they move inward when the positive terminal of the battery is connected to the red terminal of the woofer - which I understand is normal (although a little bizarre IMO). I've got the woofers back in phase and the bass is correct, but my question is, what is the proper way to wire these up? Should the black wire from the crossover go to the black terminal of the woofers? This would result in the woofers moving inwards with a positive pulse.

What was the logic of JBL wiring their woofers backwards back then anyway?



Green wire out of the crossover goes to woofer Red terminal. Black wire to woofer Black terminal (as you surmised).

There has been much discussion on why JBL chose this seemingly backward standard. I don't recall if there was ever a definitive answer found, though.

[audiomagnate]

The JBL way is the Green wire to the Red terminal on the woofer. If you start flipping the driver polarities arround you have to address how the other drivers are wired.


http://www.jblpro.com/BackOffice/ProductAttachments/JBL_TechNoteN1V12C_v5.pdf


Rob:)


That's an interesting read. Thank you. This certainly caused mass confusion in the mind of the person who worked on these in the past. One speaker is wired correctly, the other has the polarity reversed at the input terminals, and the tweeter, resulting in an out of phase woofers and mids. Bizarre. How could someone own a pair of speakers like this and not realize that something was so dreadfully wrong? No wonder he sold them, they sound pretty bad this way. Luckily, that's all that's wrong with them and the fix is a few hours of labor.

So, to sum up, black input terminal to black wire, black woofer wire to black woofer terminal and black mid wire to the black mid terminal, and black tweeter wire to red tweeter terminal, correct? And for correct absolute polarity for the woofers, connect the the amp's negative output to the positive terminal.

[DavidF]

So, to sum up, black input terminal to black wire, black woofer wire to black woofer terminal YES

and black mid wire to the black mid terminal, YES

and black tweeter wire to red tweeter terminal, NO, that doesn't sound correct. Red speaker wire to Red terminal. This makes for a change in the polarity at the driver.

And for correct absolute polarity for the woofers, connect the the amp's negative output to the positive terminal. YES, though assuming your system does not invert polarity.

[audiomagnate]

...and black tweeter wire to red tweeter terminal, NO, that doesn't sound correct. Red speaker wire to Red terminal. This makes for a change in the polarity at the driver.


The official JBL N333 crossover schematic, which shows no driver polarity at all BTW(???) shows the black input terminal connected directly to the red tweeter terminal. This puts the woofer and tweeter in phase with each other (because of the backward labeling of the woofer) and the mid with opposite phase of the woofer and tweeter. It's almost as if they were purposely trying to confuse people with this goofy woofer phasing and ambiguous schematic. This is how I have them wired now and they sound quite good.

Nelson Pass's schematic does show driver polarity, but nowhere does he mention whether the + on the woofer means real world positive or or JBL positive (i.e. negative). Could he have missed the fact that the woofers are labeled backwards? After rereading the article, I'm staring to think so. It certainly seems like a point worth mentioning, and he seems to think the woofer and mid are wired in phase in the original design, which is not the case.

[remusr]

Pre-1990's drivers and systems appear to be negative (plus to pos gives inward movement) transitioning in 1990's to positive as rest of industry. The stored JBL tech note regarding loudspeaker/driver polarity(same as Robh posted above):
http://www.audioheritage.org/vbulletin/showthread.php?32437-JBL-Technical-Notes-Volume-1-Number-12C-Polarity-Conventions-of-JBL-Pro-Tranducers
Regarding internal wiring, some JBL crossovers (4344, 4345, L200B etc) are black/gnd input to LF positive and MF/HF/UHF negatives, while others (ie 4333B, L300B) are same except wire the UHF to red/pos input. Only way to be sure is to confirm with the xo schematic.

[audiomagnate]

Pre-1990's drivers and systems appear to be negative (plus to pos gives inward movement) transitioning in 1990's to positive as rest of industry. The stored JBL tech note regarding loudspeaker/driver polarity:
http://www.audioheritage.org/vbulletin/showthread.php?32437-JBL-Technical-Notes-Volume-1-Number-12C-Polarity-Conventions-of-JBL-Pro-Tranducers
Regarding internal wiring, some JBL crossovers (4344, 4345, L200B etc) are black/gnd input to LF positive and MF/HF/UHF negatives, while others (ie 4333B, L300B) are same except wire the UHF to red/pos input. Only way to be sure is to confirm with the xo schematic.

That link and the schematic have already been posted in this thread. Thanks anyway.

[remusr]

Is there still a problem then? Sounds like you have them wired per schematic now (input gnd/black to woofer -/black, mid -/black & uhf +/red). Or what?

[audiomagnate]

Is there still a problem then? Sounds like you have them wired per schematic now (input gnd/black to woofer -/black, mid -/black & uhf +/red). Or what?

DavidF doesn't seem to think so, but I agree with you, this is the correct way to wire them. The black tweeter wire should be connected to the red tweeter terminal. Are those L300's in your avatar?

Were both 077 and and LE85 labeled backwards? I couldn't find them in the paper that lists polarity of drivers. If so, that puts the woofer and mid in phase with each other, with the tweeter out of phase, a fairly common setup.

[DavidF]

DavidF doesn't seem to think so, but I agree with you, this is the correct way to wire them. The black tweeter wire should be connected to the red tweeter terminal. Are those L300's in your avatar?

Were both 077 and and LE85 labeled backwards? I couldn't find them in the paper that lists polarity of drivers. If so, that puts the woofer and mid in phase with each other, with the tweeter out of phase, a fairly common setup.

It is confusing but I try to remember that in the design the required driver polarities are set in the wiring of the xover. So if a tweeter polarity needs to be opposite from woofer, the tweeter feed comes off the opposite input terminal. Then the assembly staff don't get bogged down trying to figure out red to driver positive or driver negative. Red (white, green, yellow, etc) is always driver positive. Black (black and green, black and white, etc) is always driver negative.

The pro tech sheet illustrates both the proper hook up for the drivers as well as the reversing of the tweeter polarity by taking the input through the driver negative. The pro model is using yellow rather than red for the high horn, though.

In the end if a different polarity seems to work better in your setup then that is the ultimate answer.

http://www.jblproservice.com/pdf/Studio Monitor Series/4333B.pdf

[ivica]

It is confusing but I try to remember that in the design the required driver polarities are set in the wiring of the xover. So if a tweeter polarity needs to be opposite from woofer, the tweeter feed comes off the opposite input terminal. Then the assembly staff don't get bogged down trying to figure out red to driver positive or driver negative. Red (white, green, yellow, etc) is always driver positive. Black (black and green, black and white, etc) is always driver negative.

The pro tech sheet illustrates both the proper hook up for the drivers as well as the reversing of the tweeter polarity by taking the input through the driver negative. The pro model is using yellow rather than red for the high horn, though.

In the end if a different polarity seems to work better in your setup then that is the ultimate answer.

http://www.jblproservice.com/pdf/Studio Monitor Series/4333B.pdf (http://www.jblproservice.com/pdf/Studio%20Monitor%20Series/4333B.pdf)

connection 2405/077 in either polarity (in my opinion) would not produce any difference in the sound, but 2420 has to be properly connected in order to suppress large deep in response around 800-1000 Hz

Ivica

[JuniorJBL]

It was said somewhere that JBL put black on ALL wires that went to the black terminal to reduce confusion when they were on the assembly line.

With that speaker if they are wired correctly and you hook up an amp + to the black input terminal you will have forward cone movement.

[audiomagnate]

It is confusing but I try to remember that in the design the required driver polarities are set in the wiring of the xover. So if a tweeter polarity needs to be opposite from woofer, the tweeter feed comes off the opposite input terminal. Then the assembly staff don't get bogged down trying to figure out red to driver positive or driver negative. Red (white, green, yellow, etc) is always driver positive. Black (black and green, black and white, etc) is always driver negative.

The pro tech sheet illustrates both the proper hook up for the drivers as well as the reversing of the tweeter polarity by taking the input through the driver negative. The pro model is using yellow rather than red for the high horn, though.

In the end if a different polarity seems to work better in your setup then that is the ultimate answer.

http://www.jblproservice.com/pdf/Studio Monitor Series/4333B.pdf

That makes total sense, especially the part about making it easy for the assembly workers. Black wires (or colored/black wires) got to black terminals and solid colored (non black) wires go to red terminals. I guess I'll have to reverse the tweeter leads to get these back to stock. Thanks so much!

EDIT: ivica, you are correct, getting 2405/077 properly phased (according to the schematic) didn't make a perceptible difference, but nonetheless it is comforting to know they are connected as Mr. Timbers intended.

Does anyone know what type/quality of caps are hiding in that black box?

[remusr]

Audio - I do have L300's up front behind the 4345's in my avatar (others are 4430's inside and 4435's on outside), hooked up to Hafler 9505 amp. Mostly listen to 4345's now as they are much more open/musical but I do still like the L300's.
The polarity paper lists 2405H(ie 077 but ferritic not alnico) and 2426H (successor to 2420/LE85 but ferritic) as negatives so I expect the even older 077 & LE85 are also negative polarity, as is 2235H LF(sorta replaces L300's home 136A or H). So the UHF is wired out of phase to MF & LF but at 8500Hz xover wavelength is about 1100/8500*12=1.55 inches which looks similar to difference in sonic centre of deeper 2235 cone so UHF/LF should be in phase and the waves from the long 12" MF horn must just work better with being wired inphase with LF but out with UHF.
Can you elaborate on what you mean as labelled incorrect?

[audiomagnate]

Audio - I do have L300's up front behind the 4345's in my avatar (others are 4430's inside and 4435's on outside), hooked up to Hafler 9505 amp. Mostly listen to 4345's now as they are much more open/musical but I do still like the L300's.
The polarity paper lists 2405H(ie 077 but ferritic not alnico) and 2426H (successor to 2420/LE85 but ferritic) as negatives so I expect the even older 077 & LE85 are also negative polarity, as is 2235H LF(sorta replaces L300's home 136A or H). So the UHF is wired out of phase to MF & LF but at 8500Hz xover wavelength is about 1100/8500*12=1.55 inches which looks similar to difference in sonic centre of deeper 2235 cone so UHF/LF should be in phase and the waves from the long 12" MF horn must just work better with being wired inphase with LF but out with UHF.
Can you elaborate on what you mean as labelled incorrect?

By "labeled incorrectly" I'm simply referring to JBL's red = negative thing. Now that I have them sorted out they're pretty spectacular. I'm trying to imagine how good one of the big four ways would sound.

[BMWCCA]

Now that I have them sorted out they're pretty spectacular. I'm trying to imagine how good one of the big four ways would sound.

:D Don't try unless you're prepared to buy!

Glad you got them working. Enjoy.