Polarity issues again

[Mr. Widget]

I just got my L88’s and bo was correct.

I never doubted him. I wouldn't say I never doubt him, but I digress.

So how does the quad setup sound?

Widget

[Wilsonj]

So how does the quad setup sound?

Widget

I will have let you know later. Right now the receiver (Marantz 2500) is in the shop. So I decided to refinish the cabs on the L88's. I'll post some pics along the way.

[Zilch]

I don't get it.

Folks WANT lobes everywhere?

[DMMD]

Since it hasn't come up in awhile.... BUMP! What a difference reading this thread can make for someone with a first pair of vintage JBL.

I did a double headspin today... it becomes very apparent when you are adding connectors to transducer input wires in order to connect with cheaper M - F faston terminals instead of the legacy nickel spring posts. Now which one was positive again?

Red to red, black to black.... except most JBL's of course...

[Alan Fletcher]

Your question is very puzzling. Why is there an issue here?

Just use standard 14 gauge lamp cord. Most have molded stripes on one of the conductors. I usually use the striped side as positive, although I believe convention is opposite, marked side negative.

In any case, just connect the striped side to the + terminal on both your receiver and the speaker, and the smooth (or unmarked) side to the - terminal on your receiver and the speaker. Do the same for all four speakers and you are in business.

There may be phase issues between the two pairs because of differences in the design and their interaction with each other... port locations, driver size, room placement, etc. In that case, use your Speakers A/B switch and only use one pair at a time depending on your preference.

-A

[B&KMan]

Sorry - late to the dance. Been travelling...

sorry for me too

Well dear Wilsonj, the great boputnam is absolutely correct, and I agree in same recommendations...

I have , in same of manys JBL peoples, one time to other, a keeped a problem to polarity for speaker, network and driver...

After verified by countersy of this great forum information of JBL my speaker LF is normal connection is go back if you put a impulse...

see for complementary info the thread and particulary post 82 & 83...


http://www.audioheritage.org/vbullet...0&postcount=82

http://www.audioheritage.org/vbullet...1&postcount=83

I expose the result of good and wrong polarisation driver response and phase... and the best is according of JBL engeneer set-up...

in this case, the LF is build to go back and if you connect other way (where sense is command) your response is lack and poor ...



Yes, confusion domain by many non standart, and difference of refresh cone kit or third part kit cone, but essentially, keep track way of egeneer JBL. and original polarity and phase JBL recommendation...

this is my 2 cents recommendations.




Jean.

[boputnam]

...What a difference reading this thread can make for someone with a first pair of vintage JBL.

Which pair did you get...?

[spaulcox]

I lived in LA 1979-1981 and finally ran into a guy who was a technecion for JBL in the late 60's, and I asked him what the deal was with this reverse polarity. According to him, back in the beginning when James first got his contract with Fender, he simply made a mistake in the first large shipment to Fender. He simply put the red post on the wrong side. He had shipped out maybe 500 drivers like this before he realized what had happened. The story says that they decided to just leave it that way, so if someone bought a replacement speaker, it would still be in phase with the original one.

As a note, if you are playing through an old Twin, Bandmaster, Showman, or any other amp with JBL speakers in it... Make the black connector (+) and the red connector (-) and you will get way more punch out of your amp.

Speaker Guy

[spaulcox]

As he should be. They do.

The 123A-1 is a rarity in JBL Land - it is POSITIVE (cone out on (+) to Red terminal). This was used in the L88 and succession early vintage L100's. However, later in life JBL reversed the wiring direction on the voicecoil and voila! - the 123A-3 which is a NEGATIVE transducer (cone in on (+) to Red terminal).

If you SEARCH with a string containing "polarity" and "123A" you will find plenty on this.

So, WilsonJ my grab is the transducers in the L88 are exactly opposite what you would want to pair them with a L100A Late model. Now, in earlier days I preferred to cross-wire AT the transducer; however, JBL issued a note on this which I posted on venerable Thread No. 9, JBL Polarity Convention - see Post #43 there. JBL recommended in a case like yours, where you need to reverse all the L88 components (two in this case) you can simply connect the speaker binding posts backwards: (+) from amp to Black.

I lived in LA 1979-1981 and finally ran into a guy who was a technecion for JBL in the late 60's, and I asked him what the deal was with this reverse polarity. According to him, back in the beginning when James first got his contract with Fender, he simply made a mistake in the first large shipment to Fender. He simply put the red post on the wrong side. He had shipped out maybe 500 drivers like this before he realized what had happened. The story says that they decided to just leave it that way, so if someone bought a replacement speaker, it would still be in phase with the original one.

As a note, if you are playing through an old Twin, Bandmaster, Showman, or any other amp with JBL speakers in it... Make the black connector (+) and the red connector (-) and you will get way more punch out of your amp.

Speaker Guy

[Harvey Gerst]

I lived in LA 1979-1981 and finally ran into a guy who was a technician for JBL in the late 60's, and I asked him what the deal was with this reverse polarity. According to him, back in the beginning when James first got his contract with Fender, he simply made a mistake in the first large shipment to Fender. He simply put the red post on the wrong side. He had shipped out maybe 500 drivers like this before he realized what had happened. The story says that they decided to just leave it that way, so if someone bought a replacement speaker, it would still be in phase with the original one.

As a note, if you are playing through an old Twin, Bandmaster, Showman, or any other amp with JBL speakers in it... Make the black connector (+) and the red connector (-) and you will get way more punch out of your amp.

Speaker Guy

Interesting story. So the reverse polarity thing only happened with speakers made for Fender?

[edgewound]

I lived in LA 1979-1981 and finally ran into a guy who was a technecion for JBL in the late 60's, and I asked him what the deal was with this reverse polarity. According to him, back in the beginning when James first got his contract with Fender, he simply made a mistake in the first large shipment to Fender. He simply put the red post on the wrong side. He had shipped out maybe 500 drivers like this before he realized what had happened. The story says that they decided to just leave it that way, so if someone bought a replacement speaker, it would still be in phase with the original one.

As a note, if you are playing through an old Twin, Bandmaster, Showman, or any other amp with JBL speakers in it... Make the black connector (+) and the red connector (-) and you will get way more punch out of your amp.

Speaker Guy

I'm sorry, but that story doesn't make sense. JBL's were manufactured that way before speakers were supplied to Fender.

[Mike Caldwell]

I'm sorry, but that story doesn't make sense. JBL's were manufactured that way before speakers were supplied to Fender.

I had the same thought. JBL's were not officially supplied to Fender as a speaker option until the blond series of amps that came out in the very early 1960's. I also don't think the Dick Dale legend of the D130 being created for him holds true as the D130 was already in production in the later 1940's. The "F" series were a Fender variation with different voice coils and surround treatments.

The latest JBL neo speakers are + forward complete with a sticker on the frame to remind you.

Mike Caldwell

[JBL 4645]

A "D" cell is the large 1.5V flashlight battery. As was noted I wouldn't hook it up and walk away, but a quick tap of the wire is enough to see which way the cone is going. The 9 volt was mentioned by some one else.

I read about the "D" cell thing years ago in a David Weems book on building speakers. He showed a little rig with a double throw switch and a battery in a tuna can, to test polarity and woofer damping in a box. You switch it back and forth and listen for an equal thump, You add or remove stuffing to make them sound as close as you can for proper closed box damping. This does work if you don't have a signal generator or other test gear.

All of my ideas are stolen from others.

Don

I guess you can place the speakers next to each other while using an SPL db meter or an RTA to analyze the (thump) to see if there same?

That was hurting my head tuning myself upside down. So I’ve reformatted the image and rotated it around for easy viewing.

[JBL 4645]

Guys I stumped onto this site early this year and found parts of it easy to understand and I sure some of you will be able to understand the most of it. It’s nicely laid out with images and lots of other technical stuff.

http://www.lenardaudio.com/education/17_cinema.html

[Harvey Gerst]

Plus, nobody who worked for JBL in the 60's would call themselves a "technician". That just wasn't a job title at JBL during that period. The JBL musical instrument "F" series speakers came about because of a unique set of circumstances:

1. As head of Quality Control, I was also head of the Repair Department; not exactly the biggest deal in the world, since the "Repair Department" consisted of one guy at the time.

2. I happened to be the only person at JBL who played electric guitar, so I was able to figure out the cause of the problems with Fender speakers being returned for repair.

And once again, for the record, Dick Dale had nothing to do with the design of any JBL speakers, and Leo Fender didn't visit JBL to ask for improvements in Fender JBL speakers.

I sent a memo to Bill Thomas, explaining the problems with musicians messing up our standard speakers, and a solution to fix them, along with a proposal for adding two more models to create a new line of musical instrument speakers - the "F" series.

The modified D130's would be called D130F's.

The modified D131's would be called D120F's.

A new 10" speaker (made up of existing parts from a D123 pot and an LE10 frame) would be called a D110F.

A new woofer would be created (from existing 15" speaker parts) and would be called a D140F.

The biggest discussion centered around renaming the D131 to the D120F. You didn't screw around with existing model designations back then. Since the D131 was very popular as a guitar speaker, I was reluctant to rename it, but having the names more consistent (i.e., 110, 120, 130, 140) also made a lot more sense to me.

My concerns were settled in about 5 minutes when Bill Thomas stopped by my desk in the factory to see how the new units were coming along. I mentioned my concerns about renaming the D131, and he didn't see that calling it a D120 would be a problem, and that was the end of it.

Either that first year, or the next, JBL took a small space at the July NAMM show in Chicago and showed the new line of MI speakers. The exhibit consisted of the four speakers, a front loaded cabinet with a snap off grill, me and my guitar, and a new MI catalog.

And that's pretty much the whole story. JBL was still a pretty small company, even after we moved from Fletcher Drive to Casitas Ave.. The move to the larger place was not to add more people, but to get more room for parking, shipping, and raw parts. Fletcher Drive was cramped for everybody and spread out over a lot of different buildings.