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wrager
01-26-2012, 11:53 AM
http://www.pispeakers.com/JBL_Polarity.pdf

So is it true that with these transducers, black is positive? I guess I'm new to the party...

Lee in Montreal
01-26-2012, 12:07 PM
http://www.pispeakers.com/JBL_Polarity.pdf

So is it true that with these transducers, black is positive? I guess I'm new to the party...

Party is over since the mid 1980s if I am not mistaken. Then JBL joined the bandwagon. A 1.5v battery is your best friend to determine the polarity of your speakers.

louped garouv
01-26-2012, 12:28 PM
how does one determine the polarity for a compression driver?

impulse testing?

boputnam
01-26-2012, 02:59 PM
JBL Technical Notes Volume 1, Number 12C - Polarity Conventions of JBL Professional Transducers (http://www.jblpro.com/catalog/support/getfile.aspx?docid=241&doctype=3)

pos
01-28-2012, 03:45 AM
how does one determine the polarity for a compression driver?

impulse testing?

Yes, holmimpusle for example will show you the thing immediately
I was surprised when I installed some truextent diaphragm to see that they also follow the "old" reversed logic, whereas their doc tell the opposite!
http://materion.com/~/media/Files/PDFs/Electrofusion/EQF3023_PrecisionDiaphragm.pdf
The "+" on their diaphragm is in fact a "-", so the doc should read "positive voltage on - terminal moves diaphragms towards phase plug"...
This is good for compatibility with older diaphragms that these are supposed to replace, but I wish their doc at least tell the truth, as I had to reinstall my diaphragms...

Mr. Widget
01-28-2012, 10:29 AM
This is good for compatibility with older diaphragms that these are supposed to replace, but I wish their doc at least tell the truth, as I had to reinstall my diaphragms...I only see this about polarity:

Polarity ........................................... Positive voltage at + terminal moves
.................................................. ..............diaphragm towards phase plug

I guess that could be correct as well as ambiguous, as in: For the vintage JBLs the positive terminal is the black one and possibly with Radians it is the red one? I don't actually know about the polarity of Radian drivers. My point being, they are saying that if you use the driver's "positive" terminal, you get a forward movement. They are not saying which terminal is the positive terminal.


Widget

pos
01-28-2012, 11:42 AM
Yes they are: there is a "+" on the diaphragm, so the doc *is* wrong
54622

grumpy
01-28-2012, 12:03 PM
Just be careful to ensure that the test system (mic/pre/line/software) has a
physically verifiable polarity. E.g., baseline with a low frequency driver that
DC can be applied to, and the excursion observed... noting if it matches
the polarity of the measured pulse with the test system.

Mr. Widget
01-28-2012, 12:14 PM
Yes they are: there is a "+" on the diaphragm, so the doc *is* wrongSo you are saying that a positive voltage on the "+" terminal of the coil does not produce a diaphragm motion towards the phase plug as the document clearly states?


Widget

pos
01-28-2012, 12:47 PM
Yes, I am positive about that ;)

When I installed the diaphragms I wanted to keep the original behavior of the JBL driver so I connected the black terminal to the + on the truextent to get a reverse polarity, but it was in phase...
I know my test setup respects polarity so I am pretty sure about this (and also the fact that now that I reconnected the red terminal to the + the popularity is the same than my other JBL drivers)

I just recheck while writing this post: my truextent with red terminal connected to the + on the diaphragm has the same polarity than my 2435.

Mr. Widget
01-28-2012, 02:05 PM
Yes, I am positive about that ;)

When I installed the diaphragms I wanted to keep the original behavior of the JBL driver so I connected the black terminal to the + on the truextent to get a reverse polarity, but it was in phase...I'll contact Truextent and see what they say about that.


Widget

AMACNEE
01-30-2012, 06:52 PM
Curious as to how to use a 1.5 volt battery to test polarity?

Mr Wizard
01-30-2012, 08:06 PM
Curious as to how to use a 1.5 volt battery to test polarity?

Connect a wire to each speaker terminal.
Touch one wire to the negative side of the 1.5 volt battery terminal and hold it in place.
Touch the other wire to the positive side of 1.5 volt battery terminal, if speaker cone pushes
outward, the wire on the positive side of 1.5 volt battery terminal is the speakers positive terminal.
If you flip the wires on the the battery the speaker cone will pull inward.

It helps to have a fresh battery. Also it is easier to see a woofer cone move than a tweeter diaphragm.

Mr Wizard

Robh3606
01-30-2012, 08:16 PM
Do not use a battery to check polarity on a compression driver. Cones only say mids and woofers where you can see the movement.

Rob:)

Mr Wizard
01-30-2012, 08:45 PM
Do not use a battery to check polarity on a compression driver. Cones only say mids and woofers where you can see the movement. Rob:) I stand corrected. Also it is easier to see mids and woofers move when checking polarity. Do not use a battery to check polarity on a tweeter/compression driver. . Mr Wizard

carolus
01-31-2012, 07:37 AM
Do not use a battery to check polarity on a compression driver. Cones only say mids and woofers where you can see the movement.

Rob:)
Hi Rob,
FYI,
1) This is my home method: with battery (even 1,5Vdc) , long bristol-paper-rule (in a V-shape) and millimeter measuring rule ...
It's very easy to see the (+) or (-) 1/10mm diapragme deplacement .... So, my JBL2482 and 2441 are now with the correct polarity,
Second method,
2) And for a total check with drivers on horn (and blind woofers in casing) i use ... "phase-it", a fine pretty tool from Gato-Audio .... (final test with cabling between amp and driver ... no mistake)

Allez, salukes & the best,
Karel
54667

Earl K
01-31-2012, 09:25 AM
Yes, holmimpusle for example will show you the thing immediatelyI was surprised when I installed some truextent diaphragm to see that they also follow the "old" reversed logic, whereas their doc tell the opposite!http://materion.com/~/media/Files/PD...nDiaphragm.pdf (http://materion.com/~/media/Files/PDFs/Electrofusion/EQF3023_PrecisionDiaphragm.pdf)The "+" on their diaphragm is in fact a "-", so the doc should read "positive voltage on - terminal moves diaphragms towards phase plug"...This is good for compatibility with older diaphragms that these are supposed to replace, but I wish their doc at least tell the truth, as I had to reinstall my diaphragms...
When I installed the diaphragms I wanted to keep the original behavior of the JBL driver so I connected the black terminal to the + on the truextent to get a reverse polarity, but it was in phase...I know my test setup respects polarity so I am pretty sure about this (and also the fact that now that I reconnected the red terminal to the + the popularity is the same than my other JBL drivers)

> Black ( on the driver ) to "+ on the TrueExtent" voice-coil gave you a positive displacement ( or "in-phase" as you mistaken call it ) just as TrueExtent says you should get ( assuming you connected a positive going pulse to the black terminal on the driver ) .

> Maybe the problem here is that you think the " minus terminal ( for any type of polarity test ) " equates to the black terminal ( on the driver ) , when in fact ,"minus" (from say a tiny, tiny battery ) goes to the red terminal ( for a polarity test ).

> This is for Legacy JBL stuff / also assuming you want to achieve a positive diaphragm displacement from a positive pulse ) .


> Language can be a tricky thing , even for the natives .

:)

PS : BTW, I don't endorse the use of batteries for this type of test .

Allanvh5150
01-31-2012, 11:35 AM
You can also do it by observing the wind direction of the coil and a compass.

Allan

pos
01-31-2012, 12:40 PM
The doc (http://materion.com/~/media/Files/PDFs/Electrofusion/EQF3023_PrecisionDiaphragm.pdf) states "positive voltage on the + terminal moves diaphragm towards phase plug", which is definitely not the case.
What else can I say :dont-know:







> Black ( on the driver ) to "+ on the TrueExtent" voice-coil gave you a positive displacement ( or "in-phase" as you mistaken call it ) just as TrueExtent says you should get ( assuming you connected a positive going pulse to the black terminal on the driver ) .

> Maybe the problem here is that you think the " minus terminal ( for any type of polarity test ) " equates to the black terminal ( on the driver ) , when in fact ,"minus" (from say a tiny, tiny battery ) goes to the red terminal ( for a polarity test ).

> This is for Legacy JBL stuff / also assuming you want to achieve a positive diaphragm displacement from a positive pulse ) .



> Language can be a tricky thing , even for the natives .

:)

PS : BTW, I don't endorse the use of batteries for this type of test .

Mr. Widget
02-01-2012, 12:16 PM
Semantics aside, I have contacted Truextent and with red faced embarrassment, they apologize for their error. Yes, in fact they have exactly duplicated JBL's diaphragm polarity convention and their spec sheet is incorrect.

Good call pos!


Widget

grumpy
02-01-2012, 01:40 PM
in fact they have exactly duplicated JBL's diaphragm polarity convention
... as one would hope for a drop-in replacement. :D I actually just assumed that was the case, ignored the spec sheet in that regard entirely, and got lucky (in not spending time chasing down a response notch that should not have been there).

Nice to get this all nailed down though.

Earl K
02-01-2012, 01:52 PM
,,,,and with red faced embarrassment, they apologize for their error. Yes, in fact they have exactly duplicated JBL's diaphragm polarity convention and,,,
their spec sheet is incorrect.
> Language can be a tricky thing , even for the natives .Well,,, at least I got that part right . ;) & Sorry for ever doubting you, pos .:crying:

:)