JBL D140F (I found two NOS)

[braud357]

I don't think it makes any difference which polarity is chosen (+ or -) as long as it's the same for multiple speakers. Let me know if I am wrong. I could be delusional, but it seems I remember thinking firing backwards (JBL's red to +) protected the speaker somehow.

They will definitely work when wired "backwards" ! Back in the 1970's (when I was a wee lad) i I decided to upgrade to JBL speakers. I loaded a couple of Peavey 2x15 cabs with D-140F 8 ohm speakers. I just knew that the red terminal on a speaker is ALWAYS positive ! I gigged with them for 3 years and was satisfied with the sound - and I never had a failure ! I only learned later on that they were reverse polarity ! (If you think that this one is good - you should hear about my adventures with "Ohms Law" !!

 

[StereoPlayer]

They will definitely work when wired "backwards" ! Back in the 1970's (when I was a wee lad) i I decided to upgrade to JBL speakers. I loaded a couple of Peavey 2x15 cabs with D-140F 8 ohm speakers. I just knew that the red terminal on a speaker is ALWAYS positive ! I gigged with them for 3 years and was satisfied with the sound - and I never had a failure ! I only learned later on that they were reverse polarity !

I did exactly the very same thing….

 

[agedhorse]

I don't think it makes any difference which polarity is chosen (+ or -) as long as it's the same for multiple speakers. Let me know if I am wrong. I could be delusional, but it seems I remember thinking firing backwards (JBL's red to +) protected the speaker somehow.

The problem with wiring them with red = + (for a factory stock one) is that the cabinet can't be combined with anything else that's been produced in the last ~35 years. Guaranteed incompatibility.

JBL's red = negative does absolutely nothing to protect the speaker.

 

[6thplanet]

Any reason JBL chose to do it that way?

 

[Redbrangus]

It was in the beginning -- the early days and there was no 'standard'. They made a decision about the polarity of their voice coils and then stuck with it, even while the industry coalesced around an opposite 'standard'. I'm sure they felt it would be too disruptive to their installed base of drivers to change until they just couldn't ignore it any longer. And sure enough, when they finally did convert to the more accepted 'standard', it did create significant confusion among dealers, users, and manufacturers who used their products. A very similar thing happened with manufacturers who used XLR connectors before the emergence of a standard as to whether pin 2 or pin 3 carried the '+' part of a balanced signal. Many of them -- especially the Brits -- had standardized on 'pin 3-hot' prior to the industry designating the standard as being 'pin 2-hot'. This is an actual, officially adopted ANSI standard; to the best of my knowledge, there is no actual standard that designates that a positive voltage supplied to the positive terminal of a loudspeaker produces a forward voice-coil motion. It's just an accepted convention.

 

[Geri O]

Any reason JBL chose to do it that way?

Somewhere way back, we were told this crazy-sounding story from a rep firm guy that would come see the band when he was in town, that JB Lansing had become pissed off at Mr. Alter Lansing and, I think, Gauss and EV as well and began manufacturing his speakers with the “backwards” black-positive standard to spite them all. Which in and of itself doesn’t make much sense. But it’s fun to think back, “remember that goofy-a$$ story that the rep firm guy told us about JBL and their wiring” kinda moment.

Right or wrong, when I first went to work at the PA company and started getting familiar with the various boxes and components, I decided, again right or wrong, that everything would be wired to push forward on the positive pulse of my Cricket polarity checker. That meant wiring up JBL components “backwards”, as in the positive wire to the black terminal. I kept up with all of this fairly easily since I was the only guy taking care of the system upkeep. And the Cricket polarity checker was my friend in those days.
And I soooo appreciated the day when JBL introduced new drivers that had changed the standard to red-positive. Geez, Luiz, already! At least they were well-labeled about the change.

Thankfully, some time after that, the owner went with just about all EAW gear and 99% of this polarity foolishness subsided. Still have to check behind the guys in the shop working on speaker cabs to be sure that replacement drivers are wired correctly.