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Author Topic: Tweeter polarity  (Read 16235 times)

Gary Weller

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Re: Tweeter polarity
« Reply #20 on: April 07, 2011, 03:13:41 pm »

I snagged a pair of used jrx115s super cheap and am starting to play with them. The speaker I am testing now looks to have had a tweeter diaphragm replacement (the horn was mounted upside down). The magnatude graph seems to loose coherence and amplitude around 2k (right where the passive crossover is set). I flipped the polarity on the tweeter and got the second graph, which is much more even. Note that I bypassed all crossovers and EQs to get those graphs. Does this imply the tweeter is out of polarity? The leads are properly connected, could this be an after-market diaphragm that was wound the wrong way? Will reversing the polarity on the tweeters solve my problem, or is there something bigger I should worry about?

Bennett could be right...it could be an after market LF 15 or even a recone kit. For years, JBL has wound their voicecoils opposite of everyone else in the industry. DC voltage to the red post drives their cones rearward instead of forward. Either the LF or HF driver could be off.

If you use subs, the jrx115s should be in phase with those as well.

As you have already learned, it is simple enough to fix with wiring.

Incorrect. Starting in the '50s JBL had standardized on a polarity convention specific to their drivers. As time went on and "MI - musical instrument" drivers became a large part of their inventory JBL began to fall in line with the rest of the industry and newer speakers were wired to the spec we accept as standard today. That is, positive voltage = voice coil moves out.
 
Because it was not possible to change entire lines or products already in production simply to meet the "MI standard" JBL began a gradual phase in of their products. They did not change existing products. Regardless of that fact mutli driver boxes, those with crossovers, should be considered "in phase", and they will be until re-wired or the crossover modified. That also includes bi-amped products where the internal wiring has taken this into account. The only time phase is an issue will be when a raw driver is used by another manufacture or home brew specialist, and then, maybe. "Fixing the wiring" is only an option if the wiring is incorrect to begin with, and I suggest some education on a subject prior to making blanket and misleading statements covering entire product lines.
 
It is best to check polarity in those cases, or any case where you may feel there is a polarity problem. You can do this by referencing JBLs white paper on the subject, the final word on JBL polarity. See below;
 
http://www.jblpro.com/catalog/support/getfile.aspx?docid=241&doctype=3

By looking at this white paper and looking at my "new" SR4732A boxes I just got, It looks like I'll have to reverse the polarity of either my subs or the jbls to get them in phase with each other, correct? My subs are positive equals outward movement.


http://www.jblproservice.com/pdf/SR-Series/SR4732A.pdf
« Last Edit: April 07, 2011, 03:16:16 pm by Gary Weller »
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Mark Chrysostom

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Re: Tweeter polarity
« Reply #21 on: April 07, 2011, 03:55:34 pm »

You need a "Cricket" tester from Galaxy. Magical little box.

http://www.galaxyaudio.com/CRICKET.jsp

As a side note, I know from experience (and JBL tech info) that many of their boxes show "reversed" polarity in the HF driver when compared to the LF. It's normal. Most of their products use spade connector of different sizes so it's impossible to hook up backwards.
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Chuck Simon

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Re: Tweeter polarity
« Reply #22 on: April 07, 2011, 04:06:04 pm »

Quote
My subs are positive equals outward movement.

So is your SR4732A, as long as it is original wiring in the cab.

From the JBL link that Bob supplied:

"SR Series (Prefix SR): all models are positive"
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Tim McCulloch

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Re: Tweeter polarity
« Reply #23 on: April 07, 2011, 04:08:21 pm »

Bennett could be right...it could be an after market LF 15 or even a recone kit. For years, JBL has wound their voicecoils opposite of everyone else in the industry. DC voltage to the red post drives their cones rearward instead of forward. Either the LF or HF driver could be off.

If you use subs, the jrx115s should be in phase with those as well.

As you have already learned, it is simple enough to fix with wiring.

 
Incorrect. Starting in the '50s JBL had standardized on a polarity convention specific to their drivers. As time went on and "MI - musical instrument" drivers became a large part of their inventory JBL began to fall in line with the rest of the industry and newer speakers were wired to the spec we accept as standard today. That is, positive voltage = voice coil moves out.
 
Because it was not possible to change entire lines or products already in production simply to meet the "MI standard" JBL began a gradual phase in of their products. They did not change existing products. Regardless of that fact mutli driver boxes, those with crossovers, should be considered "in phase", and they will be until re-wired or the crossover modified. That also includes bi-amped products where the internal wiring has taken this into account. The only time phase is an issue will be when a raw driver is used by another manufacture or home brew specialist, and then, maybe. "Fixing the wiring" is only an option if the wiring is incorrect to begin with, and I suggest some education on a subject prior to making blanket and misleading statements covering entire product lines.
 
It is best to check polarity in those cases, or any case where you may feel there is a polarity problem. You can do this by referencing JBLs white paper on the subject, the final word on JBL polarity. See below;
 
http://www.jblpro.com/catalog/support/getfile.aspx?docid=241&doctype=3


By looking at this white paper and looking at my "new" SR4732A boxes I just got, It looks like I'll have to reverse the polarity of either my subs or the jbls to get them in phase with each other, correct? My subs are positive equals outward movement.


http://www.jblproservice.com/pdf/SR-Series/SR4732A.pdf

NO.  The DC polarity of a transducer does NOT, by necessity, determine the phase behavior of 2 systems through the acoustic crossover.  You will need to determine this with an FFT analyzer.

Tim Mc
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Gary Weller

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Re: Tweeter polarity
« Reply #24 on: April 07, 2011, 05:33:10 pm »

Quote
My subs are positive equals outward movement.

So is your SR4732A, as long as it is original wiring in the cab.

From the JBL link that Bob supplied:

"SR Series (Prefix SR): all models are positive"

Somehow I missed that on the first reading, Thanks!
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Ivan Beaver

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Re: Tweeter polarity
« Reply #25 on: April 07, 2011, 05:52:00 pm »


By looking at this white paper and looking at my "new" SR4732A boxes I just got, It looks like I'll have to reverse the polarity of either my subs or the jbls to get them in phase with each other, correct? My subs are positive equals outward movement.


http://www.jblproservice.com/pdf/SR-Series/SR4732A.pdf
Maybe or maybe not.  What the POLARITY (NOT PHASE) is between different freq bands depends on quite a few different factors.  In many cases you want them to be out of POLARITY. But always in PHASE.  You can't test phase with a  battery BTW.

It all has to do with the physical placements of drivers-crossover slopes and types, eq applied and so forth.

It is the end result of a smooth phase and amplitude response that you are interested in-and it doesn't matter whether one band is out or in POLARITY (NOT PHASE!) with the adjacent band.

I am just a proud member of the POLARITY police and try to correct people when they use the term phase incorrectly.  There is a MAJOR difference.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

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Bob Leonard

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Re: Tweeter polarity
« Reply #26 on: April 07, 2011, 06:22:05 pm »


By looking at this white paper and looking at my "new" SR4732A boxes I just got, It looks like I'll have to reverse the polarity of either my subs or the jbls to get them in phase with each other, correct? My subs are positive equals outward movement.


http://www.jblproservice.com/pdf/SR-Series/SR4732A.pdf
Maybe or maybe not.  What the POLARITY (NOT PHASE) is between different freq bands depends on quite a few different factors.  In many cases you want them to be out of POLARITY. But always in PHASE.  You can't test phase with a  battery BTW.

It all has to do with the physical placements of drivers-crossover slopes and types, eq applied and so forth.

It is the end result of a smooth phase and amplitude response that you are interested in-and it doesn't matter whether one band is out or in POLARITY (NOT PHASE!) with the adjacent band.

I am just a proud member of the POLARITY police and try to correct people when they use the term phase incorrectly.  There is a MAJOR difference.

Ivan is of course correct. In this case if you refer to the schematic again you'll note two of the drivers using JBLs older standard show outward movement and the third inward movement with the cabinet connected properly to the amplifier, plus to plus, minus to minus at the input.
 
This is intentional by JBL and will confirm Ivans statement.
 
In all cases try not to over engineer the solution. Simply hook up the input cables to the speaker as stated in the owners manual. If from that point you have an issue you can always contact JBL and they will always gladly assist.
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Brian Ehlers

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Re: Tweeter polarity
« Reply #27 on: April 08, 2011, 12:52:10 pm »

I am just a proud member of the POLARITY police and try to correct people when they use the term phase incorrectly.  There is a MAJOR difference.
It doesn't help that equipment manufacturers traditionally use the greek characters theta or phi to label the polarity button.  In engineering and mathematics we use these characters to denote phase.
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Chris Davis

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Re: Tweeter polarity
« Reply #28 on: April 08, 2011, 01:53:53 pm »

I am just a proud member of the POLARITY police and try to correct people when they use the term phase incorrectly.  There is a MAJOR difference.
It doesn't help that equipment manufacturers traditionally use the greek characters theta or phi to label the polarity button.  In engineering and mathematics we use these characters to denote phase.
Very true...  Well, at least that is probably why it originated the way it did...and since audio signals are AC in nature, there you have it.   But, in this special case, you are not using AC mechanisms  to manipulate "it".  You are just flipping two wires, regardless of whatever "it" may be.

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Re: Tweeter polarity
« Reply #28 on: April 08, 2011, 01:53:53 pm »


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