Polarity issues again

[Wilsonj]

Here we go. I have gone threw most of the threads and I’m still confused. My receiver has A&B speaker engage buttons. If I put a set of L100A late (123A-3woofer) on A and a set of Nova L88 on B and engage booth buttons at the same time will I have polarity (oppositely phased drivers) issues? If you want to hang me for this I guess it’s only fitting that I supply the rope.



Jim

[Earl K]

This is Bos' territory,,, but ,

Given the two models of speakers here's my suggestion ;

(i) Hook up one of each type to the respective A & B outputs for just the right channel on your receiver . then

(ii) Put both speakers into close proximity of a rooms corner ( close = mere inches away from the wall/corner & each other)

(iii) Play bass heavy music first into one speaker & then both speakers ( attenuate as much as you can the top end & midrange content ) .

(iv) What you're doing is a listening test. If the woofers are in phase the bass will get louder when you engage the "B" button. If the sound thins out when the two woofers are played together, then they are out of phase.

(v) If the woofers are out of phase / I think I would simply flip the polarity of the cabling running to the L88s

(vi) I wouldn't worry much about the phase/polarity on the tweeter sections unless the two box types are closestacked ontop of each other. If that's the case / maybe buy bigger speakers .



:)

[Wilsonj]

This is Bos' territory,,, but ,

Given the two models of speakers here's my suggestion ;

(i) Hook up one of each type to the respective A & B outputs for just the right channel on your receiver . then

(ii) Put both speakers into close proximity of a rooms corner ( close = mere inches away from the wall/corner & each other)

(iii) Play bass heavy music first into one speaker & then both speakers ( attenuate as much as you can the top end & midrange content ) .

(iv) What you're doing is a listening test. If the woofers are in phase the bass will get louder when you engage the "B" button. If the sound thins out when the two woofers are played together, then they are out of phase.

(v) If the woofers are out of phase / I think I would simply flip the polarity of the cabling running to the L88s

(vi) I wouldn't worry much about the phase/polarity on the tweeter sections unless the two box types are closestacked ontop of each other. If that's the case / maybe buy bigger speakers .



http://audioheritage.org/vbulletin/images/smilies/smile.gif


Thanks Earl, makes sence. Now if I could only afford bigger speakers.:(

[Don Mascali]

The ol' D cell battery and a short piece of wire is a good trick. Look to see if the woofer moves in or out and hook them up acordinglly.

Edit: I have used this for compression drivers out of the box too. You stretch a piece of plastic wrap over the exit and you can see if it moves in or out. I can't ever remember which driver does what, and this is a quick and dirty check.

[Earl K]

Hi Jim'

- I'm trying to understand the genesis of your confusion & understand why you have these overall polarity concerns,,,, So , what's up ? What is it that you are trying to accomplish that concerns polarity is preventing ?

ANOTHER TEST ( I see Don as jumped in ) good !
- Another simple polarity test is the 1.5 volt battery type. Simply connect the batteries terminals to those of each speaker type ( of course they must be disconnected from amp first ) . The 1.5 volts DC is sufficient voltage to cause a visual cone displacement of the woofer. Find the battery orientation that moves the woofer cone outwards for one of your speaker models. Remember what battery connections go to which color terminal on the back of the speaker box . Repeat this exercise at the other type of speaker. Note the relative direction of cone movement in comparison to the first box. If they are both outwards then both woofer types in their own boxes are "in phase".

- It's always good to test things twice and do two types of tests to corroborate the findings .

- I've looked at the schematics for both speakers / and according to them the tweeters should be in phase if you don't revrese polarity of the speaker cables.

EDIT : ( see Bos' post at the bottom - my assumption is apparently wrong )

- So , forget what I said above about simply reversing cable polarity if one type of woofer is out of phase . If a woofer type is out of phase, flip one model type ( say the L88 ) inside the box by reversing the wires .

EDIT : ( see Bos' post at the bottom - apparently a simple switch of the polarity of the cabling going to the L88 is the way to go )

:)

[Mr. Widget]

Here we go. I have gone threw most of the threads and I’m still confused. My receiver has A&B speaker engage buttons. If I put a set of L100A late (123A-3woofer) on A and a set of Nova L88 on B and engage booth buttons at the same time will I have polarity (oppositely phased drivers) issues?

Silly question... are you using them all in the same room? If so why? If not polarity and phase don't matter.

Widget

[Earl K]

EDIT :
Jim - a AA battery is enough voltage to see sufficient cone movement for the phasing test ( I just did it ) . Don't use a 9 volt.


:)

[Mr. Widget]

I've always used a weak 1.5V D cell... works fine.

Widget

[Wilsonj]

Hi Jim'

- I'm trying to understand the genesis of your confusion & understand why you have these overall polarity concerns,,,, So , what's up ? What is it that you are trying to accomplish that concerns polarity is preventing ?


:)


Here is the reason. I have a rather large receiver 250w per side. I own a pair of L100A late. And was looking at adding another pair of speakers to the system in the same room. I thought things would be fine with that much power But then I came accross the phase issue.

[Earl K]

Hi Jim

Okay,, I get it .

Do you have enough info now to figure out the phase & polarity issues ?

:)

[rek50]

"The ol' D cell battery and a short piece of wire is a good trick" :blink: I thought a D size cell (Battery) was 1.5 Volts. Where did the 9 Volts come in? If D cell means Dry Cell then it could be many different Voltages. Or is it that you guys are just "Funnin" and trying to catch the sleepers? As you can tell I'm new here, but none the less, I enjoy reading and learning about the "Alchemy" of sound.

[Earl K]

"The ol' D cell battery and a short piece of wire is a good trick" I thought a D size cell (Battery) was 1.5 Volts. Where did the 9 Volts come in? If D cell means Dry Cell then it could be many different Voltages. Or is it that you guys are just "Funnin" and trying to catch the sleepers? As you can tell I'm new here, but none the less, I enjoy reading and learning about the "Alchemy" of sound.


- No , the 9 volt reference was from my end. All from my own bad brain / not Dons' .

- My apologies to Don for the inference and any implications made .

rek50 - Glad to see you are not asleep ! ( obviously I am )

:)

[Don Mascali]

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.:D

[Earl K]

- I've edited my previous posts to remove the 9 volt references .

- As just mentioned ,, it all started in my brain ( as an incorrect assumption on my part ) :(

[Wilsonj]

Hi Jim

Okay,, I get it .

Do you have enough info now to figure out the phase & polarity issues ?

:)

yes and no. I would need both sets of speakers to do the test to see if they are in phase with each other. At this time I only have the L100A late. I did the test on them. Positive on the battery to red on the binding post and negative on the battery to black on the binding post the cone moved in. reversed settings and the cone moved out. If I got the same results with the L88s they would be in phase with each other. Right? It would be nice to know the results of this test on the L88 before I bought the L88s.

[Mr. Widget]

It would be nice to know the results of this test on the L88 before I bought the L88s.

Why?

Who cares? Based on what your test shows they will be in phase, but so what... if they weren't you could simply flip the wires of either set. As long as they all go out (or in) with the same polarity you are good to go.

Widget

[Earl K]

Hi Jim

I wouldn't overthink this phase thing too much more.

If these L88(s) fit with your budget requirments / then buy them.

The L88 is essentially an L100 / but is lacking the 5" midrange. A quick scan of the schematics for the two crossovers also supports this view. They are very close siblings. This also means the tweeters were wired up in the same way / so tweeter phasing should not be an issue .

Running both types together to get a bigger sound should be quite successful. As Mr Widget pointed out, you'll just want to identify the polarity of the L88s' woofer , when & if you buy them. If the L88s woofers are backwards / then just flip around the wires inside the box that lead to the woofers terminals .

If you buy them and then run into a situation where you have more questions / then by all means reactivate this thread for some more input. :)

:cheers:

[Mr. Widget]

I wouldn't go flipping wires in a speaker system... unless I was designing them myself.

In this case it is a moot point as the L88s are all "old school" JBL which are reverse polarity from the standard convention. His test of his L100s revealed that his JBLs are also "old school"... no worries here.

Widget

[Mike Caldwell]

Hello

To check polarity / phase I use a Galaxy Audio polarity tester. It has two units, one sends a test pulse on either a speaker level output or at a line level output. The other unit has a built in microphone and two LED's the blink with the test pulse one is + the other is -. These are great for test compression drivers and speakers as well. The battery test is cheaper but really only works well on cone speakers. When listening to see if two cabinets are in phase I found that pink noise or FM noise between radio stations works well, when listening in the center between two speakers you can tell if there is a null from cancellation or not very easy.
Here is a link to Galaxy Audio and their ploarity tester.
http://www.galaxyaudio.com/CRICKET.html

Mike Caldwell

[Mr. Widget]

Wow at $99 the Cricket could be even cheaper than the Saran Wrap technique.:D

Widget

[Earl K]

I wouldn't go flipping wires in a speaker system... unless I was designing them myself.

In this case it is a moot point as the L88s are all "old school" JBL which are reverse polarity from the standard convention. His test of his L100s revealed that his JBLs are also "old school"... no worries here.

Yeh But, Yeh But, ( forget the "old school" conventions for now - Jim has already articulated his on going confusion after reading all the available text based descriptions )

I think that Jim is concerned that the 123A-1 and 123A-3 woofers might for some reason move in different directions when a positive voltage is applied to same-colored terminals. (That's been my interpretation of all this chitchat up to this point.) If so, then testing those actual woofer-cone movements ( with a 1.5V battery ) and then ( if need be ) synchronizing the direction of those cone movements is the obvious next step and remedy .

:)

[Wilsonj]

In this case it is a moot point as the L88s are all "old school" JBL which are reverse polarity from the standard convention. His test of his L100s revealed that his JBLs are also "old school"... no worries here.

Widget

I think I got it guys. And we did't even have to get out the rope.:)

Thank you all so much,

[boputnam]

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

I'm confused on the results of your test. Best thing would be to get the damned Cricket that Mike Caldwell speaks of, except you may not often need it. My comes in quite handy...

The 123A-3 was only used in the last of the L100's, and is a NEGATIVE transducer. All the L88's I sorted through used the 123A-1 which is a POSITIVE transducer - an oddity in this world of ours.

Here's my read of the attached tech sheets:

L100A - Late:
LF - (-)
MF - (-)
HF - (+)

Nova L88 - this is a guess. You need remove the LF and see if Red binding post connects to the GRN lead. If so...
LF - (+)
HF - (-)

The L88 ts do not specify which cabinet binding post (on the schematic) is Red. Therefore, by schematic convention the top one is Red to (in this case) GRN (going to the red terminal on the 123A-1). That would be running (+), or cone out. Your test said it tested cone in (-). Could be, but the ts's are pretty standardized that way (but not completely). If my hunch is right, your HF is out of phase with the L100A Late. Pull the LF on the L88 and check that the GRN lead connects to the Red cabinet binding post.

9-volts are overkill (and only use them on LF's if at all), but if you use a beat one they are great because the terminals just fit right onto the transducer's, making it very quick. Just drain the 9v almost to death before using.

I differ with Widget on this one - if you're cross-phased, you should wire in the cabinet to rectify, otherwise you are not getting the additive sound you hope for by pairing cabinets. However, do youself (and ensuing owners) the courtesy of labelling what you've done on the back of the cabinet.

[Wilsonj]

I'm confused on the results of your test.

The L88 ts do not specify which cabinet binding post (on the schematic) is Red. Therefore, by schematic convention the top one is Red to (in this case) GRN (going to the red terminal on the 123A-1). That would be running (+), or cone out. Your test said it tested cone in (-). Could be, but the ts's are pretty standardized that way (but not completely). If my hunch is right, your HF is out of phase with the L100A Late. Pull the LF on the L88 and check that the GRN lead connects to the Red cabinet binding post.



My test was on the L100A late 123a-3 woofer (cone in) not on the L88

[Mike Caldwell]

Hello
As Bob said only use a 9 volt batt on a woofer / cone driver. 9 volts dc straight to the voice coil of a tweeter or compression driver will not / should not burn out the voice coil if only held on it for a moment but it will stretch the diaphragm, most certainly if it is aluminum. You do that one time and the cost of the Cricket tester is not too bad. There is also another company who makes kinda the same thing only it has a test CD to play to produce the test signal. It would be more limited in what you could do with it and where but I'm sure it is less expensive. I think the Crickets are around $300 or so now.


Mike Caldwell

[boputnam]

I think that Jim is concerned that the 123A-1 and 123A-3 woofers might for some reason move in different directions when a positive voltage is applied to the similar colored terminals. 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.

[Wilsonj]

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.

That is music to my ears. Makes things simple. :applaud:

[Mr. Widget]

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.

I'll trust that our resident polarity checker, checked his facts... I knew there were some L100s that were of the non standard "old school" JBL convention which is opposite to the polarity of the rest of the speaker universe...:blah: but I admit I was too damn lazy to look for Bo's thread with the little chart in it and figured what are the odds that the venerable old L88 would be one of the few odd balls that used the basakwards voice coil...

Back to what we have all been saying... no worries, check 'em, switch 'em if necessary and you are good to go.

Widget

[boputnam]

I'll trust that our resident polarity checker, checked his facts... :blah: :blah: :blah:

Dammit, Widget!! :bash:

The "L100-series-ts" is a most relevant posting. I compiled it from the available single L100 ts's.

If read carefully it shows the transition from the 123A-1 to the 123A-3 over time. Note the two earlier iterations of the L100's have the 2213H was a (near) direct replacement for the 123A-1, but you needed to "reverse polarity". That note disappeared on the L100A Late (with it's 123A-3).

[Wilsonj]

Nova L88 - this is a guess. You need remove the LF and see if Red binding post connects to the GRN lead. If so...

LF - (+)
HF - (-)

The L88 ts do not specify which cabinet binding post (on the schematic) is Red. Therefore, by schematic convention the top one is Red to (in this case) GRN (going to the red terminal on the 123A-1). That would be running (+), or cone out.


I just got my L88’s and bo was correct. The green lead connects to both the red binding post and the red terminal on the 123A-1. Battery test (+) cone out

[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...:D

[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 :D

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/vbulletin/showpost.php?p=33180&postcount=82

http://www.audioheritage.org/vbulletin/showpost.php?p=33181&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.


:cheers:

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.:D

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.:D

[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 (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.

[Mr. Widget]

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.Since "James" had been dead since 1949, I doubt he "screwed up".:D

Seriously, since Harvey was there, I think his version of the creation of the JBL line of MI speakers is a bit more likely. :bouncy:



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.:bs:

That would only make sense if you had other speakers that were also used for the instrument and the two sets of speakers were out of phase with each other.


Widget

[Zilch]

It's apparentl that MI guys make stuff up.

SR and studio guys do the same to "enhance" their knowledge base.

[DIY guys don't do that, nope.... :p ]

[boputnam]

Just so our gentle readers get it right, now, or in the future:


Interesting story. So the reverse polarity thing only happened with speakers made for Fender?No, definately not. Most vintage JBL transducers are "negative" convention, if you will. When in-doubt, test for direction of cone movement using a 1 to 3 voltage drive.


JBL's were manufactured that way before speakers were supplied to Fender.'zactly.

And Harvey - great post. Always enjoy the sharing some of your history at JBL!! :)

[JBL 4645]

What’s the best way of testing for polarity with an oscilloscope?

[jblbgw_man]

What’s the best way of testing for polarity with an oscilloscope?

Use a dual channel cro minimum, on channel one have a split of the input "reference" tone and set the internal trigger to this channel, either use a microphone or sample the speaker drive (amp output) with channel 2 or if it is bi amped then also sample the other speaker drive on channel 3, selecting apropriate time base and setting up for dual trace or quad trace if you are lucky enough to have one. You should see a "time shift" in the horizontal trace with reference to the referenced input (input 1), if the signal is phase shifted with the original source, the horizontal time shift will represent the phase delay, if your cro has markers set them at the peak of each sine wave, use the graticules on the display with reference to the time base setting and work out the shift, or if it's a smart cro then you can achieve this using your delta markers. 180 degree phase shift will be very obvious as the sine wave will look somewhat inverted to the referenced input signal...... hope this helps ....good luck!:D

[Harvey Gerst]

Just so our gentle readers get it right, now, or in the future:



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

No, definately not. Most vintage JBL transducers are "negative" convention, if you will. When in-doubt, test for direction of cone movement using a 1 to 3 voltage drive.

And Harvey - great post. Always enjoy the sharing some of your history at JBL!! :)
Yeah, my "question" was asked with tongue planted firmly in cheek.

[boputnam]

Yeah, my "question" was asked with tongue planted firmly in cheek.I know - it was brilliant. I worry for the newbies here who may not suss out our sense of humor. :D

[Don Mascali]

JBL 4645 said,
"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?"


No, the little tester I was talking about was to check the damping on a single "Closed Box" woofer. When optimally damped the sound made on make and break are about the same. You can then add or remove stuffing to adjust.
Putting two speakers together is usually done to check phasing between them.

[JBL 4645]

Use a dual channel cro minimum, on channel one have a split of the input "reference" tone and set the internal trigger to this channel, either use a microphone or sample the speaker drive (amp output) with channel 2 or if it is bi amped then also sample the other speaker drive on channel 3, selecting apropriate time base and setting up for dual trace or quad trace if you are lucky enough to have one. You should see a "time shift" in the horizontal trace with reference to the referenced input (input 1), if the signal is phase shifted with the original source, the horizontal time shift will represent the phase delay, if your cro has markers set them at the peak of each sine wave, use the graticules on the display with reference to the time base setting and work out the shift, or if it's a smart cro then you can achieve this using your delta markers. 180 degree phase shift will be very obvious as the sine wave will look somewhat inverted to the referenced input signal...... hope this helps ....good luck!:D

jblbgw_man

Thank for that brief information there. If I stumble across a cheap (oscilloscope) in a second-hand store I’ll look for those findings that you commented on, again thank you.

bop

One rather simple, question the (polarity) on the (JBL 2240) sub when attached with a 1.5v battery gives inverted motion the driver is being pulled backwards.

So should the sub be wired up with (+ on to –) rather than (+ on to + and – onto -)

Thanks.:)

[JBL 4645]

JBL 4645 said,
"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?"


No, the little tester I was talking about was to check the damping on a single "Closed Box" woofer. When optimally damped the sound made on make and break are about the same. You can then add or remove stuffing to adjust.
Putting two speakers together is usually done to check phasing between them.

Don

I was doing a test rather early this morning, in fact I haven’t slept since yesterday. Anyway I placed the SPL db metre within 28in away from the sub and noted the (thump) at 70dbc for the only brief moment when the terminals where connected. I for got to set the microphone up to the preamp and test in on the RTA,

I’m tired I’m getting some sleep now before I crack up.:snore:

[spaulcox]

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.


This is great information... I was bewildered by this reverse polarity thing and vulnerable to any explanation. The only mystery that still remains is why did Fender apply (or wire) the positive output to the negative (red) terminal of the JBL drivers? When I first discovered this in 1970, I was in a band with a guitar player using a dual showman with 2 D130's. When we re-wired them polarity correct, the difference in punch was very noticeable. Also when JBL manufactured their own cabinets like the 4560, those cabinets were wired polarity correct. (negative or sleeve to RED.) Several responses suggest that it makes no difference as long as all drivers are the same. Wrong! If you are miking a kick drum and the initial attack is forward, but the signal transmitted to your drivers is backward, you lose the initial punch in the chest. Not to mention the actual drum will be out of phase with your sound system. You don't want the initial attack of any wave form sucking in. Why did JBL not supply any notation on the speaker itself, or on the white paper that came in the box, to let us know that these terminals are backwards from everyone else in the world??? I also wondered how the original designer made the decision to make the red terminal negative. Being a speaker building hobbyist who as a pro musician have always built my own PA enclosures, you take for granted that RED IS HOT.

[louped garouv]

perhaps the "conventions" were not yet established

[spaulcox]

Great work Harvey!

JBL should keep these speakers in production. I use the E-110 as a mid driver in my studio monitors, and the E-120 as mid drivers in my PA system. Their upper mid frequencies are so transparent (they make a Sax sound exactly like a Sax.)

Now to get them we have to go to E-bay. I saw a pair of unopened K-120's go for $1700


Speaker Guy :applaud:

[Harvey Gerst]

Okay, I now have a personal theory about why the old JBL speakers had negative polarity, but I'll need some of you speaker rebuild guys to confirm it. I just thought about it today. Here goes:

On the old JBL speakers, there was very little voice coil overhang; i.e., the voice coil height was basically similar to the gap length. I had speakers come into the repair department that actually had the voice coil popped out of the gap. It was a rare occurrence, but I saw several examples of that during my days at JBL.

So, my theory is that good old Jim Lansing understood that a loud positive pop coming through an amp could push the speaker cone forward, clean out of the gap, while that same pop to a negative polarity speaker would slam the coil back into the basket, but that negative slam would cause less damage to the speaker than an outgoing pop would.

You'd hit the voice coil to cone glue joint, and that would absorb some of the shock.

Anyway, that's my personal theory as to why the original JBL speakers had reverse polarity. In all the years I spent at JBL, I never thought to ask anybody why we did it that way. I'm sure George Martin or Howard Wieser probably knew the real reason.

[boputnam]

...why did Fender apply (or wire) the positive output to the negative (red) terminal of the JBL drivers? Back in the day, JBL's polarity "was" the convention! :)


...Being a speaker building hobbyist who as a pro musician have always built my own PA enclosures, you take for granted that RED IS HOT.Always best to check. Especially when someone might have had their grubbies inside something you just purchased, and either intentionally or mistakenly got it wrong.

Always best to check. Get the Cricket (http://www.galaxyaudio.com/CRICKET.jsp)...


Okay, I now have a personal theory about why the old JBL speakers had negative polarity ... I just thought about it today. Harvey, that is the most cogent reason I've heard. Would certainly have solved the "They're jumping the gap!!" issue... Nice one.

[boputnam]

If you are miking a kick drum and the initial attack is forward, but the signal transmitted to your drivers is backward, you lose the initial punch in the chest. Not to mention the actual drum will be out of phase with your sound system. Be careful not to confuse electrical polarity with acoustic (time) phase.

Merely by position of the subs, they are typically out-of-phase with the kick drum and bass (and with the Mains, too, if physical separation is sufficient).

Know your λ (lambda)...;)

[DavidF]

"This is great information... I was bewildered by this reverse polarity thing and vulnerable to any explanation..."

Compression drivers had to "pull" on the voice coil. I can easily see a small engineering group establishing a standard that positive going current pulls in all drivers, woofers or horn drivers. JBL chose to go all coils the same, Altec chose to have woofers different from their compression drivers. Ain't it that simple, after all?

I still hold that since I can't be sure that every one of my vinyl and digital disks, and each and every cut on same, are outputting absolute polarity, then I can't also pretend it makes a difference if my woofers Woof or Moof.

[boputnam]

I still hold that since I can't be sure that every one of my vinyl and digital disks, and each and every cut on same, are outputting absolute polarity, then I can't also pretend it makes a difference if my woofers Woof or Moof.I really like that...

:p

Well done.

[indycraft]

To woof or to moof........that is the question?


Compression drivers had to "pull" on the voice coil. I can easily see a small engineering group establishing a standard that positive going current pulls in all drivers, woofers or horn drivers. JBL chose to go all coils the same, Altec chose to have woofers different from their compression drivers. Ain't it that simple, after all?

I still hold that since I can't be sure that every one of my vinyl and digital disks, and each and every cut on same, are outputting absolute polarity, then I can't also pretend it makes a difference if my woofers Woof or Moof.

[grumpy]

... or foow/foom, ... fwiw. :)

[spaulcox]

Okay, I now have a personal theory about why the old JBL speakers had negative polarity, but I'll need some of you speaker rebuild guys to confirm it. I just thought about it today. Here goes:

On the old JBL speakers, there was very little voice coil overhang; i.e., the voice coil height was basically similar to the gap length. I had speakers come into the repair department that actually had the voice coil popped out of the gap. It was a rare occurrence, but I saw several examples of that during my days at JBL.

So, my theory is that good old Jim Lansing understood that a loud positive pop coming through an amp could push the speaker cone forward, clean out of the gap, while that same pop to a negative polarity speaker would slam the coil back into the basket, but that negative slam would cause less damage to the speaker than an outgoing pop would.

You'd hit the voice coil to cone glue joint, and that would absorb some of the shock.

Anyway, that's my personal theory as to why the original JBL speakers had reverse polarity. In all the years I spent at JBL, I never thought to ask anybody why we did it that way. I'm sure George Martin or Howard Wieser probably knew the real reason.



Speaker Guy:

The only twist on all that is that JBL knew the RED post was negative, so when they used their drivers in their own enclosures they wired them accordingly so that a positive charge moved the speakers forward. I like the first story I heard about this, in that it was simply a mistake in initial production. They had shipped large quantities in the beginning before they even realized they were wired backwards, then decided to keep it that way so that the next batch would be in sync with the previous ones.

[spaulcox]

Be careful not to confuse electrical polarity with acoustic (time) phase.

Merely by position of the subs, they are typically out-of-phase with the kick drum and bass (and with the Mains, too, if physical separation is sufficient).

Know your λ (lambda)...;)


Speaker Guy;

Good graph, so you want your subs in phase with your kick drum, unless you have your mains 87 feet out front of the stage. At this point you want to reverse the polarity of your subs 180 degrees.

[Harvey Gerst]

Speaker Guy:

The only twist on all that is that JBL knew the RED post was negative, so when they used their drivers in their own enclosures they wired them accordingly so that a positive charge moved the speakers forward.
Except, the positive signal from an amp went to the Red terminal on the x-over, and the black terminal of the Crossover went to the black of all the drivers. So, after exiting the network, the positive signal out of the x-over went to the speakers Red terminal, which resulted in the speakers moving backward, into the gap. At least, that's how I remember it on the N500, N1200, N2500, etc..

Again, this is as I recall, from 40+ years ago.

[spaulcox]

Except, the positive signal from an amp went to the Red terminal on the x-over, and the black terminal of the Crossover went to the black of all the drivers. So, after exiting the network, the positive signal out of the x-over went to the speakers Red terminal, which resulted in the speakers moving backward, into the gap. At least, that's how I remember it on the N500, N1200, N2500, etc..

Again, this is as I recall, from 40+ years ago.

Speaker Guy;

I'm not sure why this is so interesting to me... but it is. The old 4560 and those Scoop bass bins from the seventies (they had the single and duel 15 design) were wired so that positive (tip) of the phone plug advanced the speakers forward. Also a 12dB per octave passive crossover network flops the phase 180 degrees. The more recent SR4715 with two 2226H, which I own 4 of, also move forward with positive.

I still think they just made a mistake in the beginning??? I have worked with Altec, Utah, Jensen, Peavey, McCaulley, Eminence, Celestion, Yamaha, Carvin, EV, Community, Cerwin Vega, Oxford, Rola, Community, Grundig, Olson, Weber, Cleveland, Heppner, and several more. JBL is the only speaker I've seen with RED negative.

PS Don't get me wrong... out of all of those... JBL drivers are my favorites. I also really miss the D, K, & E series. I understand the alnico shortage, but liked the "E" series too. JBL should really bring them back!

[Domino]

I just got my Cricket yesterday for Phase checking. What a great unit!!
http://www.musiciansfriend.com/product/Galaxy-CPTS-PolarityContinuity-Test-Set?sku=421165&src=3SOSWXXA